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  • 2951.
    Zenkert, Dan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Hallström, Stefan
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Wennhage, Per
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Higher education in sandwich structures2003Konferansepaper (Annet vitenskapelig)
  • 2952.
    Zenkert, Dan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Jacques, Eric
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Multifunctional Composite Materials using Lithium Ion Functionalization2015Inngår i: International Conference on Composite Materials 20, ICCM-20, Copenhagen, Denmark, 2015, Copenhagen: ICCM , 2015Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this paper we show how one can functionalise carbon fibres by using them as an electrochemicalelectrode. The electrochemical process is the same as in a lithium-ion battery cell so that the carbonfibres act as an active electrode in future structural battery concepts. The functionalization of carbonfibres using lithium ion intercalation reveals three novel and interesting possibilities enabling carbonfibres composites to obtain several other multi-functionalities. These are strain sensing, actuation andenergy harvesting.We have found that by intercalating lithium ions into the nano-/micro-structure of carbon fibres apiezo-electrochemical effect is revealed. This is observed as a change in the potential of the carbon fibreelectrode when applying a mechanical load. The response is direct and easily measurable being in theorder of several mV. This can be utilised as a strain sensor since there is a relation between the potentialchange and the strain in the carbon fibre.Secondly, we have measured substantial axial expansion of carbon fibres when intercalated withlithium ions. The strain measured is as high as 1%. Since the stiffness of carbon fibres is very high, thiscorresponds to very large forces. This can be used for actuation or morphing.Thirdly, the newly found piezo-electrochemical effect can be used to harvest energy by convertingmechanical work to electrical energy. Applying a tensile force to carbon fibre bundles used as Liintercalatingelectrodes results in a response of the electrode potential of a few mV which allows, at lowcharge rates, discharge at higher electrode potential than at charge. More electrical energy is therebyreleased from the cell at discharge than provided at charge, harvesting energy from the mechanical workof the applied force.

  • 2953.
    Zenkert, Dan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Kaufmann, Markus
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Åkermo, Malin
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Optimisation of Composite Stuctures: Design for Cost2011Inngår i: International Conference for Composites 21st Century: Current and Future Trends / [ed] B. Dattaguru, et al, 2011Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Components made in composite material can lower the weight of structures significantly. The higher production and material cost, however, require the application of novel design strategies which allow for the cost-efficient production of these components. A methodology for a combined cost/weight optimization of composite components is presented herein. The objective function is formed by a simplified form of direct operating cost, i.e. by a weighted sum of the manufacturing cost and the component weight. The parameter that governs the balance between manufacturing cost and weight is called weight penalty and incorporates the effect of fuel burn, environmental impact or contractual penalties due to overweight. In addition, a non-destructive testing model is implemented that calculates design allowables of a laminate based on ultrasonic scan parameters. In a case study, the effect of the laminate quality on the direct operating cost is discussed. It is investigated how the permissible flaw size and therefore the scan pitch of a composite laminate can influence the optimal solution in terms of cost and weight; thus, the manufacturing cost, the non-destructive testing cost and the weight of a component can be balanced by optimizing the laminate quality in an early design phase. The optimization framework also contains a draping simulation in combination with a detailed cost estimation package and the calculation of the structural performance based on FE. First, a draping knowledge database is generated in which combinations of seed points and reference angles are evaluated in terms of fibre angle deviation, scrap, ultrasonic cuts and material shear. Second, the cost/weight optimization framework picks the best sets of plies during the subsequent optimization. By means of parametric studies it is shown that the design solution strongly depends on the magnitude of the weight penalty. It is also shown that the non-destructive testing affects the cost and choice of design concept and the permissible flaw size should be altered in order to save both weight and cost. Finally, the methodology is tested by means of a curved C-spar which is designed using plain weave and unidirectional prepreg. Different objectives in the generation of the draping database lead to different design solutions.

  • 2954.
    Zenkert, Dan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Kazemahvazi, Sohrab
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Burman, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Fatigue of foam core sandwich beams under localized loads2011Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Sandwich structures offer significant weight savings in many structural applications due to their high stiffness and bending strength to weight ratios. However, one Achilles heal of sandwich structures is their poor capability to carry localized loads. In this paper we investigate the fatigue behavior of sandwich beams subjected to localised loads.

  • 2955.
    Zenkert, Dan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Kazemahvazi, Sohrab
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Burman, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Fatigue of sandwich beams under localised loads2011Inngår i: ICCM International Conferences on Composite Materials, 2011Konferansepaper (Fagfellevurdert)
  • 2956.
    Zenkert, Dan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Lindbergh, Göran
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Johansson, Mats
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Carbon fibre composites as batteries, sensors, actuators and energy harvesting2019Inngår i: International Conference on Composite Materials ICCM22, 2019Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Reduced mass for improvements in system performance has become a priority for a wide range of applications that requires electrical energy and includes load-bearing components. Use of lightweight materials has been identified as key for successful electrification of future transport solutions. Structure, energy storage and energy distribution are usually subsystems with the highest mass contributions but energy storage and energy distribution devices are structurally parasitic. One creative path forward is to develop composite materials that perform several functions at the same time – multifunctional materials. Combining functions in a single material entity will enable substantial weight savings on the systems level.

    One such concept is a structural battery, a material that simultaneously carry load and stores energy like a battery. Structural batteries employ carbon fibres as structural reinforcement and negative electrode and can also be used as current collectors to save additional weight.

    A number of new physical phenomena when using carbon fibres as battery electrodes have been found which allows for further multi-functionality. These are all based on the fact that carbon fibres intercalated lithium ions as an electrode material. The ion intercalation creates a reversible longitudinal expansion of the carbon fibres which could be used for actuation and morphing. A piezo electrochemical effect couples the electrical potential of the fibre to the strain acting on it, which can be used for sensing purposes. By combining the expansion and the piezo electrochemical effect one can convert mechanical energy to electrochemical energy, providing an energy harvesting function. The long-term vision of this work is to create a composite material that carries load, stores electrical energy, senses its own state, morphs and harvests energy.

  • 2957.
    Zenkert, Dan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Shipsha, Andrey
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Bull, Peter
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Hayman, Brian
    Det Norske Veritas, Norway.
    Damage tolerance assessment of composite sandwich panels with localised damage2005Inngår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 65, nr 15-16, s. 2597-2611Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The work described herein is part of a larger context in which the effect of damage in sandwich composite structures for marine applications has been investigated. The overall aim of this effort has been twofold: to develop and verify existing damage assessment models to be used to assess the effect of damage on marine sandwich structures, and to develop a damage assessment scheme to be used by shipyards, ship owners and navies. More specifically, this paper presents a sub-set of this overall effort looking at impact and indentation damage and its effect on the load carrying capacity of state-of-the-art carbon composite sandwich panels for marine applications. Damage types are modelled based on physical observations from tests. Testing is then performed on different scales in order to validate the models. The overall aim is to use such models to produce information that can be used for decision-making at two levels. The first is to evaluate the damage tolerance of ship structural components and thus to calculate the size and extent of damage that a component can have without risk of growth or failure at ultimate local or global loads on the entire ship. The second is to have information at hand to decide if, and when, a structural part needs to be repaired if damage has been detected. A scheme developed for this purpose is presented herein. Finally the paper will briefly describe a common framework for damage assessment in composite sandwich structures. Herein, models are used in conjunction with the design specifics and functional requirements to create a scheme for repair decisions.

  • 2958.
    Zenkert, Dan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Shipsha, Andrey
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Burman, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Fatigue of closed cell foams2005Inngår i: Sandwich Structures7: Advancing with Sandwich Structures and Materials / [ed] Thomsen, OT; Bozhevolnaya, E; Lyckegaard, A, Springer Netherlands, 2005, s. 171-181Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper deals with fatigue of closed cell foams. The main idea is to use a few simple tests to predict the tension-tension fatigue properties of foams. The required testing consists of crack propagation rate measurements and one tension-tension fatigue test performed at yield stress for the foam. This data can then be combined to construct a synthetic S-N Curve for the foam. Tests on three densities of Divinycell H-grade foam are performed and the results Support this approach. Some preliminary results from two densities of Rollacell WF-grade are given as well. Static properties of foams scale with relative density and once this scaling can be obtained through various static tests and the same scaling appears to be valid for both crack propagation rates and fatigue properties of foams. The implication of this is that once the fatigue behaviour of one relative density foam is established, one can predict the fatigue behaviour of all other relative density foams within the same class of materials.

  • 2959.
    Zenkert, Dan
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Shipsha, Andrey
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Burman, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Fatigue of closed cell foams2006Inngår i: Journal of Sandwich Structures and Materials, ISSN 1099-6362, E-ISSN 1530-7972, Vol. 8, nr 6, s. 517-538Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The static properties of foams scale with relative density and scaling can be obtained through various static tests. The same scaling appears to be valid for both crack propagation rates and fatigue properties of the foams. This implies that, once the fatigue behavior of one relative density foam is established, one can predict the fatigue behavior of all other density foams within the same class of materials. This study deals with fatigue of closed cell foams. The main idea is to use a few simple tests to predict tension-tension fatigue properties of foams. The required testing consists of crack propagation rate measurements and one tension-tension fatigue test performed at the yield stress of the foam. This data can then be combined to construct a synthetic S-N curve for the foam. Testing is performed on three densities of Divinycell H-grade and three densities of Rohacell WF-grade foam. A very simple fatigue model, based on an initial flaw approach, is used to link the crack propagation rate behavior of these foams with their unnotched fatigue life. This approach is backed up by the experimental results. The results obtained can be used to form some general conclusions about the fatigue of closed cell foams, at least of the types used herein.

  • 2960.
    Zetterberg, Mikaela
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Kastby, Claes
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Vibrationsmätningar på handhållna pneumatiska verktyg.2011Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Nuvarande riktlinjer för hur man skall bedöma och klassificera risken för att skador skall uppstå då hand- armsystemet utsätts för vibrationer är baserade på en enkel frekvensviktningskurva. Problemet med dagens rådande standard är att den inte tar hänsyn till alla de faktorer som inverkar på risken med vibrerande handhållna verktyg, t.ex. påverkan av transienter i vibrationerna eller mängden energi som absorberas av hand- armsystemet. Ett annat problem med standarden är att karaktärisering utifrån den tenderar att bli metodoberoende beroende på vilken analysmetod som väljs. Ett sätt att ta hänsyn till fler av de bidragande faktorerna är att använda andra analysmetoder, än de som används i enlighet med rådande standard, som till exempel vibration power absorption eller analytisk wavelettransform. Vidare har de två olika i standarden rekommenderade analysmetoderna, viktningsfilter på smalband och viktningsfaktorer på tersband, applicerats var sin gång på två olika inspelade tidssignaler, en med tydliga toner och en med starka transienter, för att utröna huruvida det blir någon skillnad beroende på vilken analysmetod som väljs och därmed se hur metodberoende karaktäriseringen är. Experimenten visar att de olika analysmetoderna ger olika resultat. Viktningsfaktorer på tersband ger ett resultat som skiljer sig mot viktningsfilter på smalband och påverkar den totala handvägda accelerationen, . Vibrationens karaktär så som tydliga toner i signalen samt deras frekvens är troliga orsaker till varför de olika analysmetoderna ger olika resultat. Resultaten kan användas vid val av analysmetod för att optimera utfallet. Noteras skall dock att vidare forskning och undersökning bör genomföras för att ta reda på hur tonens lokalisering, inom tersbandet, i frekvensplanet samt hur urvalet av frekvenser för summering av påverkar utfallet av för tersband.

  • 2961.
    Zetterberg Wallin, Georg
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Crétier, Matthieu
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    A supervised learning approach to estimate the drivers impact on fuel consumption: A heavy-duty vehicle case study2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The aim of this Master thesis is to provide a statistical analysis of the factors inuencing the fuel consumption, with a focus on the separation of the drivers' performance. The study is focused on the long haulage trucks, which correspond to the application where the fuel consumption becomes of primary interest from the economical point of view. Further developments of the work leads to a graphical representation of the outcomes on a map, highlighting in particular the segments of the road network having the highest variation of the driver-inuenced fuel consumption. The analysis dataset created is the combination of data coming from di erent sources and additional features computed based on them. The datasources are providing respectively the vehicles' operating data and congurations, the road network's characteristics and the weather information. The results obtained prove that it is possible to isolate the driver factor from the overall fuel consumption. This can be achieved by training a model composed by variables statistically chosen through a regression procedure. Further in the analysis the di erent driver factors are used in order to determine the fuel saving potential of the road stretches where the factors are computed. The results are gathered in multiple stages, based on the dimension of the dataset considered and the method used. Two methods are used to train the model: the least squares regression and the ridge regression. First the whole Swedish road network composed by primary roads is analyzed with least squares. 1195 road stretches belonging to this network present a dened and di erent than zero fuel saving potential varying between 0.003 and 83.71 l/100km. Then, a smaller portion of the same road network is analyzed after being provided with road slope information. The fuel saving potential estimated using ridge regression present values between 0.002 and 24.39 l/100km.

    From the geographical point of view little can be deduced from the analysis of the complete network. The E4 provided with slope data, on the contrary, allows a better insight, especially using ridge.

  • 2962.
    Zetterström, Jeanette
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Design Methodology for Protective Structures of Glass Fibre Reinforced Plastic Exposedto Trawling2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Complex subsea oil and gas components installed on the seabed require protective structures,traditionally made of steel or glass fibre reinforced plastic – GRP. The most critical load case is trawlfishing, where trawl weights of several tons are dragged along the seabed.This master thesis work aims to develop a design methodology for such protective GRP covers and is acontinuation of the master theses work performed by REINERTSEN Jonas Elgered and Marco Nikolic in2011.The trawl load case, which is suitable for a dynamic analysis since much energy is transferred over ashort period of time, is modelled with LS DYNA, using one model built up with shell elements and onewith thick shell elements.The idea is for the methodology to work as a tool for evaluating lamina thicknesses and layups for earlycover-geometry designs.

  • 2963. Zhan, Ouyang
    et al.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Persson, Ingemar
    Nilsson, Richard
    Bik, Ulf
    Investigation of Causes for Wheel Squeal on Roslagsbanan in Stockholm2013Konferansepaper (Annet vitenskapelig)
  • 2964.
    Zhang, Jingwen
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Influence of suspension modellingon predicted ride comforton passenger rail vehicles2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The purpose of this this report was to find the sources that led to the deviation between the simulation and measurement on the ride comfort evaluation of a high-speed train. This report consists of a literature study, introduction of the train where the measurement was taken on, result analysis and sensitivity test of the secondary suspension. The literature study focused on the modelling of secondary suspensions and the simulation of rail vehicles. The predicted results were compared with the measured results. Furthermore, comparison was carried out among three different secondary suspension concepts. The secondary suspensions went through a sensitivity test to see how the parameters influence the ride comfort evaluation of the rail vehicle.It was figured out that the main deviation between the simulation and the measurement was focused on a carbody where a hydraulic damper was introduced. The difference was mainly at 1.3Hz and between 7.5Hz and 9Hz.With the main deviations figured out, the sources that might influence the ride comfort evaluation was tested. It showed that the detail of track measurement had influence on the ride comfort evaluation. More detailed measurement should be carried out if higher agreement is wanted. The secondary suspensions went through a sensitivity test. The key parameters and their influence on ride comfort evaluation was pointed out. This report can be a guidance if further tuning on the parameters of the secondary suspensions are needed.

  • 2965.
    Zhang, Meng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Cheemakurthy, Harsha
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Ehlers, Soeren
    Norwegian Univ Sci & Technol, Trondheim, Norway.;Hamburg Univ Technol, D-21073 Hamburg, Germany..
    von Bock und Polach, R. U. Franz
    Hamburg Univ Technol, D-21073 Hamburg, Germany..
    Garme, Karl
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Burman, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    ICE PRESSURE PREDICTION BASED ON THE PROBABILISTIC METHOD FOR ICE-GOING VESSELS IN INLAND WATERWAYS2018Inngår i: PROCEEDINGS OF THE ASME 37TH INTERNATIONAL CONFERENCE ON OCEAN, OFFSHORE AND ARCTIC ENGINEERING, 2018, VOL 8, AMER SOC MECHANICAL ENGINEERS , 2018, artikkel-id V008T07A038Konferansepaper (Fagfellevurdert)
    Abstract [en]

    With increasing need to utilize inland waterways (IWW), the design for IWW vessels gains attention both from a transport efficiency and an emission control point of view. The primarily issue is to estimate the ice pressure acting on the ship hull for inland waterways. Ice information for Lake Malaren is extracted and analysed in this work. Since the ice properties have great influence on the impact load, they are studied based on empirical formulae and are calibrated by reference data. The ice impact is then predicted for an inland water barge. Probabilistic method is selected to derive the load based on available field test data. Several parent datasets are chosen, and different design strategies are implemented to evaluate the ice impact load and investigate the influences from exposure factors. The paper finds that the design curve of alpha = 0.265a(-0.57) can be used for Lake Malaren. The approach itself introduces a possible way to investigate loads on ice affected IWW.

  • 2966.
    Zhang, Meng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Cheemakurthy, Harsha
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Ehlers, Soren
    Hamburg University of Technology.
    Polach, R. U. Franz von Bock und
    Hamburg University of Technology.
    Garme, Karl
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Marina system.
    Burman, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Ice Pressure Prediction Based on the Probabilistic Method for Ice-Going Vessels in Inland Waterways2018Inngår i: Journal of Offshore Mechanics and Arctic Engineering-Transactions of The Asme, ISSN 0892-7219, E-ISSN 1528-896X, Vol. 141, nr 2, artikkel-id 021501Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With increasing need to utilize inland waterways (IWW), the design for IWW vessels gains attention both from a transport efficiency and an emission control point of view. The primarily issue is to estimate the ice pressure acting on the ship hull for inland waterways. Ice information for Lake Mälaren is extracted and analysed in this work. Since the ice properties have great influence on the impact load, they are studied based on empirical formulae and are calibrated by reference data. The ice impact is then predicted for an inland water barge. Probabilistic method is selected to derive the load based on available field test data. Several parent datasets are chosen, and different design strategies are implemented to evaluate the ice impact load and investigate the influences from exposure factors. The paper finds that the design curve of α = 0.265α-0.57 can be used for Lake Mälaren. The approach itself introduces a possible way to investigate loads on ice affected IWW.With increasing need to utilize inland waterways (IWW), the design for IWW vessels gains attention both from a transport efficiency and an emission control point of view. The primarily issue is to estimate the ice pressure acting on the ship hull for inland waterways. Ice information for Lake Mälaren is extracted and analysed in this work. Since the ice properties have great influence on the impact load, they are studied based on empirical formulae and are calibrated by reference data. The ice impact is then predicted for an inland water barge. Probabilistic method is selected to derive the load based on available field test data. Several parent datasets are chosen, and different design strategies are implemented to evaluate the ice impact load and investigate the influences from exposure factors. The paper finds that the design curve of α = 0.265α-0.57 can be used for Lake Mälaren. The approach itself introduces a possible way to investigate loads on ice affected IWW.

  • 2967.
    Zhang, Meng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Marina system. KTH Royal Institute of Technology.
    Cheemakurthy, Harsha
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Marina system.
    Garme, Karl
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Marina system. KTH, Tidigare Institutioner (före 2005), Farkost- och flygteknik.
    Burman, Magnus
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner. KTH, Tidigare Institutioner (före 2005), Farkost- och flygteknik. KTH, Tidigare Institutioner (före 2005), Flygteknik.
    An Analytical Model for Ice Impact Load Prediction2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

     For ships running on ice-covered waters, the ice impact load on ship structure shall be carefully considered. This paper proposes an analytical model which takes two most important ice failure modes, localized crushing and bending breaking, into consideration. The energy method is introduced to estimate the crushing force and the indentation displacement for different scenarios. Ice bending breaking scenario is simplified as a semi-infinite plate under a distributed load resting on an elastic foundation. The two ice failure modes are assumed to share the same contact area. This model is useful to predict the ice impact load and creates a bridge between design parameters (ice properties and ship geometry) and structure loads. 

  • 2968.
    Zhang, Mengmeng
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik.
    Application and Development of the CEASIOM-SUMO-EDGE Suite for Rapid AeroData Assessment of Aircraft Flying Qualities2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In aircraft design, methods for rapid aerodata assessment and data screening at early stages are instrumentalin reducing development cost and first-time-right processes. New efficient tools for the analysis can easethe transition as the traditional and rigidly structured sequential design process gives way to a concurrentmulti-disciplinary process with the compressed time-span required in the competition for market shares.

    The CEASIOM-SUMO-EDGE software suite provides a way from initial sizing to stability and control design andassessment, including effects of aero-elasticity.

    CEASIOM ongoing and further development is driven by user needs, and the thesis reports on fourdifferent design and analysis cases which required enhancement of CEASIOM in several respects.

    The validation study on the B-747 with its multitude of control surfaces required generalizationof control surface definition and modeling. The clean-sheet design of the TransCruiser Mach 0.97passenger transport required compilation, fusion, and screening of aerodynamics data from many sourcesand in different formats. The DanBus and the asymmetrical twin-prop pusher-puller configuration required translationof geometry representation and development of simple propeller models in the automatic meshgeneration and CFD analysis.

    The way forward is provided by adoption of common data formats and geometry (and structural, etc.)modeling conventions. To this end the current proprietary XML format should be replaced by a more generalXML system such as CPACS under development at DLR which will be made public in the near future.

  • 2969.
    Zhang, Mengmeng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Cristofaro, M.
    Wang, Y.
    Da Ronch, A.
    Rizzi, Arthur
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Investigating the piaggio avanti design using CEASIOM2014Inngår i: 29th Congress of the International Council of the Aeronautical Sciences, ICAS 2014, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In early steps of aircraft design the unification of configuration definition is important to avoid user-input errors. Also coupling with each other can strengthen different tools with different specifications simultaneously provided that the geometry definition is transferred with minimum data loss. This is vitally useful especially when geometry data is transferred in order to perform high- fidelity analysis. This paper reports the analysis for the pitch control of a three-lifting-surface aircraft Piaggio Avanti using CEASIOM, a tool- chain software for aircraft preliminary design, with the baseline configuration coming from the conceptual design code AAA, linked by a common name-space CPACS for the means of data collaboration.

  • 2970.
    Zhang, Mengmeng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Nangia, R.
    Rizzi, Arthur
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Design and shape optimization of morphing winglet for regional jetliner2013Inngår i: 2013 Aviation Technology, Integration, and Operations Conference, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Aerodynamic shape optimization on a 3D laminar wing with winglet at transonic speed is studied, with two parallel redesigns come out. The inviscid drag is improved and its pressure distribution has been refined. The winglet folded angle also effects the wing loading and its root bending moment.

  • 2971.
    Zhang, Mengmeng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Rizzi, Arthur
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Aerodynamic wing shape optimization based on the computational design framework CEASIOM2017Inngår i: Aircraft Engineering, ISSN 0002-2667, Vol. 89, nr 2, s. 262-273Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose - A collaborative design environment is needed for multidisciplinary design optimization (MDO) process, based on all the modules those for different design/analysis disciplines, and a systematic coupling should be made to carry out aerodynamic shape optimization (ASO), which is an important part of MDO. Design/methodology/approach - Computerized environment for aircraft synthesis and integrated optimization methods (CEASIOM)-ASO is developed based on loosely coupling all the existing modules of CEASIOM by MATLAB scripts. The optimization problem is broken down into small sub-problems, which is called "sequential design approach", allowing the engineer in the loop. Findings - CEASIOM-ASO shows excellent design abilities on the test case of designing a blended wing body flying in transonic speed, with around 45 per cent drag reduction and all the constraints fulfilled. Practical implications - Authors built a complete and systematic technique for aerodynamic wing shape optimization based on the existing computational design framework CEASIOM, from geometry parametrization, meshing to optimization. Originality/value - CEASIOM-ASO provides an optimization technique with loosely coupled modules in CEASIOM design framework, allowing engineer in the loop to follow the "sequential approach" of the design, which is less "myopic" than sticking to gradient-based optimization for the whole process. Meanwhile, it is easily to be parallelized.

  • 2972.
    Zhang, Mengmeng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik.
    Rizzi, Arthur
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik.
    RDS-SUMO: From lofting to physics-based grids2012Inngår i: Aircraft Engineering, ISSN 0002-2667, Vol. 84, nr 3, s. 140-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Purpose - The goal for this paper is to bring the easy-to-use geometry drawing software RDS to a "solid" mesh, which could be analyzed and simulated in CEASIOM, to enhance both CEASIOM and RDS's capabilities. Design/methodology/approach - The RDS-SUMO interface is developed based on the feature that both RDS and SUMO define their geometric model using cross-sectional information, i.e. their "universe" shapes are close to each other. Findings - The translation is automated and allows the engineer to easily modify and augment the geometry in the process. Two test cases are shown, with their high quality Euler mesh and CFD computations. The A321-look-alike test case tests the mesh quality for transonic aerodynamics, such as high-speed trim and drag divergence; the twin-prop asymmetric aircraft is a "diffi+cult" non-conventional configuration analyzed for yaw stability in one-engine out mode. Practical implications - This paper shows that the CFD solutions based on solid grids could be obtained once the design is proposed and the RDS wireframe model is available. The aerodynamic properties can then be predicted in early design stage, which is very efficient for preliminary aircraft design. Originality/value - This fast meshing tool could obtain "working" grids of a new design within hours.

  • 2973.
    Zhang, Mengmeng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik.
    Rizzi, Arthur
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik.
    Meng, Pengfei
    KTH, Skolan för teknikvetenskap (SCI).
    Nangia, Raj
    Amiree, Rafiz
    Swedish Research Defence Agency (FOI).
    Amoignon, Olivier
    Swedish Research Defence Agency (FOI).
    Aerodynamic Design Considerations and Shape Optimization of Flying Wings in Transonic Flight2012Inngår i: 12th AIAA Aviation Technology, Integration, and Operations (ATIO) Conference and 14th AIAA/ISSM17 - 19 September 2012, Indianapolis, Indiana, American Institute of Aeronautics and Astronautics, 2012, s. 1-17Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper provides a technique that minimize the cruise drag (or maximize L/D) fora blended wing body transport with a number of constraints. The wing shape design isdone by splitting the problem into 2D airfoil design and 3D twist optimization with a frozenplanform. A 45% to 50% reduction of inviscid drag is nally obtained, with desired pitchingmoment. The results indicate that further improvement can be obtained by modifying theplanform and varying the camber more aggressively.

  • 2974.
    Zhang, Mengmeng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik.
    Rizzi, Arthur W.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik.
    Nicolosi, Fabrizio
    De Marco, Agostino
    Collaborative Aircraft Design Methodology using ADAS linked to CEASIOM2014Inngår i: 32nd AIAA Applied Aerodynamic Conference, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The aircraft design stages, conceptual and preliminary, are necessarily collaborative bytheir very nature. An example design carried out in this paper brings the collaborativeaspects of design to life by two academic groups, one in Naples and one in Stockholm, usingtheir own tools ADAS and CEASIOM, working respectively on conceptual and preliminarydesign. The ADAS tool is primarily empirically-based design methodology, and the CEA-SIOM tool is primarily physics-based design methodology. The example chosen is a FAR-23compliant 16-seat twin turboprop aircraft. The high-wing configuration resulting from theADAS conceptual design is the down-selected to CEASIOM where a water-tight model of thegeometry is constructed, a volume grid is generated and 16 flight conditions are simulatedby solutions of the Euler equations, some with propeller off, and others with propellerin order to judge the effect of the propeller wash over the main wing and horizontal tailsurface. Detailed comparisons between ADAS results and CEASIOM results for stability &control characteristics are carried out. In general there is reasonable agreement betweenthe two sets, considering that the empiricisms in ADAS account for viscous effects where asthe CEASIOM are purely inviscid (but nonlinear). The largest discrepancy appears in thepitching moment contribution from the horizontal tail, and various explanations for thisare suggested, including possible effects of the main wing downwash and wake on the tail.

  • 2975.
    Zhang, Mengmeng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Tomac, Maximillian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Wang, Cong
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Rizzi, Arthur
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Variable fidelity methods and surrogate modeling of critical loads on X-31 aircraft2013Inngår i: 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013, American Institute of Aeronautics and Astronautics, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a method for effcient creation of the aerodynamic database for the X-31 experimental aircraft, from low fidelity (Euler) and high fidelity (RANS) CFD. The challenge is to obtain good data for extreme flight conditions. A co-Kriging interpolation model for aerodynamic moments, forces and span loads is used, with an additional decision support system (DSS) using Proper Orthogonal Decomposition for data reduction.

  • 2976.
    Zhang, Mengmeng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik.
    Wang, C.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik.
    Rizzi, Arthur
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik.
    Nangia, R.
    Hybrid feedback design for subsonic and transonic airfoils and wings2014Inngår i: 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014, National Harbor, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A hybrid inverse/optimization method for subsonic/transonic airfoil and wing shapedesign is presented with application to a range of airfoil and wing cases, in preparation forthe test cases defined for the Special Session of SciTech 2014. The method is hybrid in thesense that it combines the traditional inverse design technique with an optimization pro-cedure that determines the optimum target pressure distribution. This paper emphasizesthe first part, the development of SCID, the Surface Curvature Inverse Design method,the theory upon which it is based, including many of the details involved with shocks,smoothing and cross flow. The application of SCID to wing design poses many challenges,and how they are met is discussed in the context of a number of inverse design test casesfor airfoils and wings. The procedure works well for airfoils, whereas twist optimizationfor transonic wings remains a challenge. The real benchmarks for our hybrid approach arethe three Optimization Discussion Group design problems. Solutions are presented for thedrag minimization of the NACA airfoil along with the wing twist optimization problem,and conclusions are drawn from the results obtained. Work has started on the drag mini-mization of the CRM wing in transonic flight, and final results will be presented in a futurepaper.

  • 2977.
    Zhang, Tao
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Marina system.
    Analysis of Active Gyro Based Roll-Stabilization of Slender Boat Hulls2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Currently, traffic congestion often happens in big cities every day. People demand a new conceptual vehiclewhich has a slender shape to reduce space, lightweight structure to decrease the fuel consumption andinnovative technology to adapt for multiple transportation conditions. NEWT is such a conceptual amphibious vehicle that satisfies people's requirements. However, everything has two sides. Slender shape and high centre of gravity will result in instability. When NEWT runs in low speed, it easily gets rolled over. In order to make up for its drawback, gyro-stabilizer has been applied to the vehicle. By tilting the rotational gyro, it generates a counter torque counteracting the roll motion to make the vehicle recover to an upright position.Therefore this master thesis analyses the original stability of the vehicle and the possible improvement by adding the gyro system for both land and water-conditions. The model can handle the problem that thevehicle meets periodic disturbance forces, such as wave excitation force and wind force.

  • 2978.
    Zhang, Wenliang
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. National Engineering Laboratory for Electric Vehicles and the Collaborative Innovation Centre for Electric Vehicles in Beijing.
    Wang, Zhenpo
    School of Mechnical Engineering, Beijing Institute of Technology.
    Zou, Changfu
    Department of Electrical Engineering, Chalmers University of Technology.
    Drugge, Lars
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Nybacka, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Fordonsdynamik.
    Advanced Vehicle State Monitoring:: Evaluating Moving Horizon Estimators and Unscented Kalman Filter2019Inngår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 68, nr 6, s. 5430-5442, artikkel-id 8682143Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Active safety systems must be used to manipulate the dynamics of autonomous vehicles to ensure safety. To this end, accurate vehicle information, such as the longitudinal and lateral velocities, is crucial. Measuring these states, however, can be expensive, and the measurements can be polluted by noise. The available solutions often resort to Bayesian filters such as the Kalman filter, but can be vulnerable and erroneous when the underlying assumptions do not hold. With its clear merits in handling nonlinearities and uncertainties, moving horizon estimation (MHE) can potentially solve the problem and is thus studied for vehicle state estimation. This paper designs an unscented Kalman filter, standard MHE, modified MHE and recursive least squares MHE to estimate critical vehicle states, respectively. All the estimators are formulated based upon a highly nonlinear vehicle model that is shown to be locally observable. The convergence rate, accuracy and robustness of the four estimation algorithms are comprehensively characterised and compared under three different driving manoeuvres. For MHE-based algorithms, the effects of horizon length and optimisation techniques on the computational efficiency and accuracy are also investigated.

  • 2979. Zhang, Z.
    et al.
    Kabral, R.
    Nilsson, B.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Revisiting the cremer impedance2017Inngår i: Proceedings of Meetings on Acoustics, Acoustical Society of America , 2017, nr 1Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In a classical paper (Acustica 3, 1953) Cremer demonstrated that in a rectangular duct, with locally reacting walls, there exits an impedance (”the Cremer impedance”) that maximizes the propagational damping for the lowest mode. Later (JSV 28, 1973) Tester extended the analysis to include a plug flow and ducts of both circular and rectangular cross-section. One limitation in the work of Tester is that it simplified the analysis of the effect of flow only considering high frequencies or well cut-on modes. This approximation is reasonable for large duct applications, e.g., aero-engines, but not for many other cases of interest. Kabral et al. (Acta Acustica united with Acustica 102, 2016) removed this limitation and investigated the’exact’ Cremer impedance for circular ducts including flow effects. As demonstrated in that paper the exact solution exhibits some special properties at low frequencies, e.g., a negative real part of the wall impedance. In this paper the exact Cremer impedance is further analyzed and discussed. Also, the exact solution for rectangular ducts is presented. 

  • 2980.
    Zhang, Zhe
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Optimal damping and slow sound in ducts2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The thesis is dedicated to expanding knowledge on two duct acoustic issues including: 1) the optimal damping of low frequency sound and 2) the development and application of ‘slow sound’.

    To address the first issue, the ‘Cremer impedance’ proposed more than half a century ago has been revisited and further developed. The original motivation is to extend the concept from large duct applications, such as aero-engines, to low frequency applications including vehicle intake and exhaust or cooling and ventilation systems. This leads to the derivation of the ‘exact’ solution of the Cremer impedance for single-lined rectangular ducts valid in the low frequency range in the presence of a ‘plug’ flow. A substantial improvement in the low frequency damping is achieved with the exact solution and a measurement campaign is carried out to validate this.

    However, for both circular and rectangular ducts (including single-lined and double-lined types) the exact solution of the Cremer impedance has a negative real part in the low frequency range. This indicates that an active boundary is required to provide the optimal damping. Two investigations on the negative resistance are conducted. First, the ‘plug’ flow is replaced by a sheared flow by changing the boundary condition in the optimization model. With this modification, the Cremer impedance is recalculated and the negative resistance is still found in most cases, demonstrating that the negative resistance is not necessarily an artefact of the boundary condition. Second, since the Cremer impedance is based on mode-merging, a mode-merging analysis is carried out. The merging result shows that the downstream results are always valid, but some of the upstream results in the low frequency range are invalid in the sense that unexpected mode pairs merge, and the corresponding damping is smaller than expected. This finding is true for both the fundamental mode and higher order modes.

    Regarding the second issue, ‘slow sound’ or sound with a much reduced ‘phase velocity’ is investigated using a resonant periodic system in the low frequency range. This can be seen as an acoustic metamaterial where sound propagates at a much smaller-than-normal speed around its resonance frequency. Following a hydrodynamic particle agglomeration model, the slow sound is applied to manipulate the distribution of small particles in the vehicle exhaust system. Although in principle this acoustic agglomeration method can work, it will only be efficient if the wave damping in the metamaterial is kept small. 

  • 2981.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    The Cremer Impedance: An Investigation of the Low Frequency BehaviorManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The Cremer impedance, first proposed by Cremer (1953) and then extended by Tester (1973), is supposed to give the maximum propagation damping in an infinitely long waveguide. Previous works including a uniform grazing flow have shown negative resistance in the low frequency range for both circular and 2-D rectangular waveguides, i.e., implying an active boundary. In order to further analyze the low frequency behaviour of the Cremer impedance, especially the negative resistance, two investigations are conducted in the current work. First, the previously used Ingard-Myers boundary condition is replaced by the Brambley boundary condition with the introduction of a thin inviscid boundary layer, and results obtained with the two boundary conditions are compared to see the effect of a sheared flow. The frequency range where the two boundary conditions can be applied is also analyzed. Second, discussions regarding the validity of the low frequency result in both the up- and downstream directions from the perspective of mode-merging are presented. This analysis is further extended from the fundamental mode to higher order modes in the frequency range where they are ‘just cut-on’.

  • 2982.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    The Cremer impedance: An investigation of the low frequency behavior2019Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 459, artikkel-id 114844Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Cremer impedance concept based on mode merging is one method that can substantially improve the axial damping in a waveguide. Previous works on the Cremer impedance including a uniform grazing flow have exhibited unexpected phenomenon such as negative resistance in the low frequency range. The current paper is a continuation of earlier works by the authors to extend the investigation of the Cremer impedance with a focus on the low frequency range. Two independent investigations from the perspective of boundary layer effects and mode merging patterns are conducted to better understand the low frequency behavior of the Cremer impedance.

  • 2983.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Lin, D.
    Xiaodong, J.
    Investigation of the 'exact' cremer impedance2018Inngår i: 25th International Congress on Sound and Vibration 2018, ICSV 2018: Hiroshima Calling, International Institute of Acoustics and Vibration, IIAV , 2018, s. 1810-1817Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Cremer impedance, first proposed by Cremer (Acustica 3, 1953) and then improved by Tester (JSV 28, 1973), refers to the locally reacting boundary condition that can maximize the attenuation of a certain acoustic mode in a uniform waveguide. One limitation in Tester's work is that it simplified the analysis on the effect of flow by only considering high frequencies or the 'well cut-on' modes. This approximation is reasonable for large duct applications, e.g., aero-engines, but not for many other cases of interest such as the vehicle intake and exhaust systems. A recent modification done by Kabral et al. (Acta Acustica united with Acustica 102, 2016) has removed this limitation and investigated the 'exact' solution of Cremer impedance, which reveals an appreciable difference between the exact and classic solution in the low frequency range. A measurement campaign is here carried out to experimentally demonstrate such difference. In addition, the exact solution is found to exhibit some special properties at very low frequencies, e.g., a negative resistance. One can question if this negative resistance is physically correct or an artefact of the assumption of a plug flow profile and the use of the so-called Ingard-Myers boundary condition. To investigate this the Cremer solution is here extended to the case with a more general and realistic flow profile, using a modified version of the Ingard-Myers condition suggested by Brambley (AIAA J 49(6), 2011).

  • 2984.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Tiikoja, Heiki
    KTH.
    Peerlings, Luck
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Experimental Analysis on the 'Exact' Cremer Impedance in Rectangular Ducts2018Inngår i: SAE technical paper series, ISSN 0148-7191, Vol. 2018-June, nr JuneArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cremer impedance, first proposed by Cremer (Acustica 3, 1953) and then improved by Tester (JSV 28, 1973), refers to the locally reacting boundary condition that can maximize the attenuation of a certain acoustic mode in a uniform waveguide. One limitation in Tester's work is that it simplified the analysis on the effect of flow by only considering high frequencies or the 'well cut-on' modes. This approximation is reasonable for large duct applications, e.g., aero-engines, but not for many other cases of interest, with the vehicle intake and exhaust system included. A recent modification done by Kabral et al. (Acta Acustica united with Acustica 102, 2016) has removed this limitation and investigated the 'exact' solution of Cremer impedance for circular waveguides, which reveals an appreciable difference between the exact and classic solution in the low frequency range. Consequently, the exact solution can lead to a much higher low-frequency attenuation level. In addition, the exact solution is found to exhibit some special properties at very low frequencies, e.g., a negative resistance. In this paper, liners designed on the basis of the exact solution are tested and the difference between the exact and classic solution in the low frequency range (not low enough to go into the negative resistance region) is experimentally investigated.

  • 2985.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Tiikoja, Heiki
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Experimental analysis of whistle noise in a particle agglomeration pipe2018Inngår i: INTER-NOISE 2018 - 47th International Congress and Exposition on Noise Control Engineering: Impact of Noise Control Engineering, Institute of Noise Control Engineering , 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A self-sustained sound, more usually known as a whistle, refers to a distinct tonal noise created due to the interaction between the sound and flow field. When a positive feedback loop is formed between the two fields, the energy in the mean flow will be transferred into the sound wave, thus giving rise to a whistle. In engineering practice, whistles are destructive as they can produce high sound and vibration levels and may result in risk for mechanical failures. In this work, a flow-related high level tonal noise was found during a measurement on a particle agglomeration pipe, which is a quasi-periodic corrugated structure designed for the exhaust system of heavy-duty trucks. The purpose of the pipe is to enhance particle agglomeration to increase the size of exhaust gas particles. To investigate the origin of the detected tonal noise additional measurements were carried out. Based on the measurement result, the aero-acoustic coupling in the agglomeration pipe was analyzed, revealing that the pipe has a large potentiality to amplify the incident sound power in the presence of a mean flow. Furthermore, the Nyquist stability criterion was applied to confirm the existence of exponentially growing modes in the system at certain conditions.

  • 2986.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    ‘Double-’ and ‘Triple-root’ Cremer Impedancefor a Rectangular Duct with Opposite Lined WallsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    To achieve high low frequency damping in an infinitely long double-lined rectangular duct with zero mean flow, the optimization of axial sound attenuation in the sense defined by Cremer (i.e., using the ‘Cremer impedance/solution’ concept) is examined for the fundamental mode. Two double-root Cremer impedance solutions that merge a mode pair into a single mode are presented. Different mode-merging patterns due to symmetry are found for these two solutions. As an extension, two triple-root Cremer impedance solutions (including one with a negative resistance) that merge three modes are also provided by extending the optimum condition proposed by Cremer. The two triple root solutions are theoretically advantageous in damping compared with the double root solutions, and the advantage is explained from the perspective of mode-merging.

  • 2987.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI).
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Karlsson, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Katoshevski, D.
    Particle Number Reduction in Automotive Exhausts Using Acoustic Metamaterials2017Inngår i: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 10, nr 4, s. 1566-1572Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Air pollution caused by exhaust particulate matter (PM) from vehicular traffic is a major health issue. Increasingly strict regulations of vehicle emission have been introduced and efforts have been put on both the suppression of particulate formation inside the engine cylinders and the development of after-treatment technologies such as filters. With modern direct injected engines that produce a large number of really small sub-micron particles, the focus has increased even further and now also includes a number count.The problem of calculating particle trajectories in flow ducts like vehicle exhaust systems is challenging but important to further improve the technology. The interaction between particles and oscillating flows may lead to the formation of particle groups (regions where the particle concentration is increased), yielding a possibility of realizing particle agglomeration. The oscillating flow may simply be hydrodynamic or as assumed here: the flow oscillations are created by sound propagation rather than hydrodynamic approaches. An analysis is presented which gives the relationship between the speed of sound, the mean flow velocity and the amplitude of the acoustic particle velocity for particle agglomeration to be feasible. It is shown that it can be achieved if the convective speed of sound is reduced to the same order as the mean flow velocity. It is therefore suggested to use the so-called acoustic metamaterials, which can help control, direct and manipulate sound waves. At this stage a phenomenological 1D model is used for the analysis, which allows the authors to build an understanding of the effect of the sound waves and flow oscillations on particle motion and paves the way for further analysis on particle agglomeration.

  • 2988.
    Zhendong, Liu
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Anders, Rønnquist
    NTNU Norwegian University of Science and Technology.
    Numerical Study on the Dynamic Behaviour of Railway Catenary Overlap Section for Higher Speed2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The dynamic behaviour in the contact between pantograph and catenary decides the quality of power transmission, the component service life and the maximum operational speed. The catenary system is desired to be built smooth and uniform in geometry and elasticity along the train-running direction, but due to electric concerns and tensile force retention, the entire catenary is made up by many tensioning sections. To make a pantograph smoothly shift between the neighbouring sections, an overlap of several spans is introduced to work as a transition zone. However, when the pantograph is passing through the overlap section, its dynamic behaviour can be heavily changed and cannot sustain as good contact as in the middle spans of each tensioning section. To clarify the dynamic behaviour in this special section and to ensure a stable contact between pantograph and catenary, a numerical study on catenary section overlap is performed based on a 3D pantograph-catenary finite element (FE) model. The following issues are discussed in this paper: operational speed, wire gradient, damping ratio, and spacing distance in multi-pantograph operation. The results show that the gradient of wires in overlap sections and the damping ratio have great influence on the dynamic performance, especially at high speed and in multi-pantograph operation. In practice, in the overlap section the gradient should be properly designed and some additional damping is beneficial to ensure good dynamic performance for higher speed.  

  • 2989.
    Zhenrui, Wang
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Noise Radiation from Automotive Turbochargers2011Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Turbochargers are now commonly used in modern automotive engines, which increase the density of air entering the engine to produce more power. This device not only greatly improves the degree of engine efficiency, but also reduces the pollutant emissions. However, one of the important issues which must be considered is the noise from turbochargers. This noise can radiate either after propagation through the intake and exhaust ducts or via induced vibrations in the turbocharger housing. Here the in duct sound will be studied and normally this cause problems mainly on the intake side where there is less silencing available. In particular noise from high frequency tones as well as surge noise phenomena can cause noise problems.The main aerodynamic noise from centrifugal compressors are blade tone noise, buzz-saw noise and flow separation (or surge) noise. For instance the tones occurring at blade passing frequencies can be a problem for large turbochargers,e.g., as found on trucks, where they lie in the range around 10 kHz. The most efficient way to achieve quieter machines is the reduction of the sources, therefore it is important to be able to measure and investigate the sound generation ofturbo chargers.In this thesis work the sound generated has been investigated using a dedicated turbocharger acoustic test rig. The main purpose is to investigate methods for estimating the in-duct acoustic power using a micro-phone array. Three differen tmodels are proposed to estimate the power in the propagating acoustic modes and to suppress the flow noise. In order to test the proposed methods experiments have been performed on an automotive compressor at four different operating conditions. The results are compared with the literature in order to identify the dominating sound generation mechanisms.

  • 2990. Zhou, H.
    et al.
    Lopez-Arteaga, Ines
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. Eindhoven University of Technology, Netherlands.
    Nijmeijer, H.
    Broadband planar nearfield acoustic holography based on one-third-octave band analysis2016Inngår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 109, s. 18-26Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Planar nearfield acoustic holography (PNAH) is usually based on narrow-band, single frequency analysis, which is time consuming when the source behavior over a broad frequency range is of interest, as is the case with many industrial sources. In this paper a method, broadband planar nearfield acoustic holography based on one-third-octave band analysis (BPNAH), is described. Data relating to the complex band pressure on the hologram is obtained by combining the root-mean-square pressure corresponding to a one-third-octave band with the phase of the pressure corresponding to a single frequency line. Numerical simulations and measurements show that the BPNAH method allows a significant reduction in processing time, while keeping a similar accuracy to the conventional reconstruction, which is based on the summation of frequency by frequency in the corresponding band. As a simple, time-saving and robust technique, the BPNAH method is particularly well adapted to industrial studies.

  • 2991. Zhou, J.
    et al.
    Karlsson, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Study of thermoacoustic engine for automotive exhaust waste heat recovery2019Inngår i: SAE technical paper series, ISSN 0148-7191, Vol. 2019-April, nr AprilArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, the travelling-wave thermoacoustic engine (TAE) and its application for recovery of waste heat from automotive exhaust systems is investigated. The aim is to give some insight into the potential, but also limitations of the technique for practical applications. This includes packaging, physical boundary conditions as heating and cooling available, but also system perspectives as influence of legislative drive cycles and degree of hybridization. First, the travelling-wave TAE is described as a low-order acoustic network in the frequency domain. Models, including non-linear effects, are set up for every component in the network to describe the propagation and dissipation of acoustic waves. For a TAE with looped structure, the continuity of pressure and volumetric velocity is employed to determine the saturation pressure, as well as the stable operating point. These models are validated against experimental data available in the literature [1]. This is an engine designed for high-temperature application, but is well documented and yields a good reference for the models and to further the understanding of the TAE. Next, an optimized design for a system to be adapted to the operating conditions typical for heavy-duty systems is studied and proposed. No actual physical prototype has been built and verified, but the design is based on, and is of the same efficiency, as machines that have been reported in the literature. The proposed design and the original TAE are then used to discuss the practical implementation for heavy- and light-duty vehicles on a system level. To improve the utilization of the available exhaust waste heat, a configuration of system heat exchangers combining a self-circulating loop with multiple TAE modules is preliminarily studied. Further research for this configuration is needed for practical implementation although current simulation results are encouraging.

  • 2992.
    Zhou, Jiewei
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Attitude Determination and Control of the CubeSat MIST2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The ADCS concept in MIST reects the limitations of the CubeSat in terms of space, power and onboard computer computational capability. The control is constrained to the use of only magnetic torquers and the determination to magnetometers and Sun sensors in spite of the the under-actuation and underdetermination during eclipses. Usually small satellites with a similar ADCS and demanding requirements fail, therefore MIST would be a design reference for this kind of concept in the case it succeeds.

    The objectives of this thesis work are the feasibility assessment of the concept to meet the nominal requirements in MIST and the consideration of alternatives. Firstly, the importance of gravitational stabilization and di erent congurations for the inertial properties are analyzed based on the linear stability regions for nadir pointing spacecraft. Besides, extended stability regions are derived for the case when a momentum wheel is used to consider alternative options for passive stabilization in terms of the inertial properties. Then a controller based on the Asymptotic Periodic Linear Quadratic Regulation (AP LQR) theory, the currently most extended and e ective for pure magnetic control in small satellites, is assessed. Also a Liner Quadratic Regulator design by means of numerical optimization methods, which has not been used in any real mission, is considered and its performances compared with the AP LQR. Regarding attitude determination a Linear Kalman Filter is designed using the AP LQR theory. Finally, a robustness analysis is conducted via Monte Carlo simulations for those control and determination strategies.

  • 2993.
    Zhou, Lin
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strömningsakustik.
    Acoustic characterization of orifices and perforated liners with flow and high-level acoustic excitation2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis is motivated by the need for noise control in aircraft engine with orifices and perforated liner. The presence of high-level acoustic excitation, different flow situations either bias flow, grazing flow or any combination in the aircraft engine, makes the acoustic behavior complex due to the interaction between sound and flow over the lined wall. Both systematic acoustic prediction of aircraft engines and liner optimization necessitate progress in impedance measurement methods by including the effect of the complex flow situations. The aim of the present thesis is to experimentally study the change in acoustic properties of orifices and perforated liners under bias or grazing flow.

    In order to study the effect of different combinations of bias flow and high-level acoustic excitation, an in-duct orifice has been investigated with finely controlled acoustic excitation levels and bias flow speeds. This provides a detailed study of the transition from cases when high-level acoustic excitation causes flow reversal in the orifice to cases when the bias flow maintains the flow direction. Nonlinear impedance is measured and compared, and a scattering matrix and its eigenvalues are investigated to study the potentiality of acoustic energy dissipation or production. A harmonic method is proposed for modelling the impedance, especially the resistance, which captures the change in impedance results at low frequencies compared with experimental results.

    The presence of grazing flow can increase the resistance of acoustic liners and shift their resonator frequency. So-called impedance eduction technology has been widely studied during the past decades, but with a limited confidence due to the interaction of grazing flow and acoustic waves. A comparison has been performed with different test rigs and methods from the German Aerospace Center (DLR). Numerical work has been performed to investigate the effect of shear flow and viscosity. Our study indicates that the impedance eduction process should be consistent with that of the code of wave propagation computation, for example with the same assumption regarding shear flow and viscosity. A systematic analysis for measurement uncertainties is proposed in order to understand the essentials for data quality assessment and model validation. The idea of using different Mach numbers for wave dispersion and in the Ingard-Myers boundary condition has been tested regarding their effect on impedance eduction. In conclusion, a local Mach number based on friction velocity is introduced and validated using both our own experimental results and those of previous studies.  

  • 2994.
    Zhou, Lin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    A systematic uncertainty analysis for liner impedance eduction technology2015Inngår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 356, s. 86-99, artikkel-id 12557Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract The so-called impedance eduction technology is widely used for obtaining acoustic properties of liners used in aircraft engines. The measurement uncertainties for this technology are still not well understood though it is essential for data quality assessment and model validation. A systematic framework based on multivariate analysis is presented in this paper to provide 95 percent confidence interval uncertainty estimates in the process of impedance eduction. The analysis is made using a single mode straightforward method based on transmission coefficients involving the classic Ingard-Myers boundary condition. The multivariate technique makes it possible to obtain an uncertainty analysis for the possibly correlated real and imaginary parts of the complex quantities. The results show that the errors in impedance results at low frequency mainly depend on the variability of transmission coefficients, while the mean Mach number accuracy is the most important source of error at high frequencies. The effect of Mach numbers used in the wave dispersion equation and in the Ingard-Myers boundary condition has been separated for comparison of the outcome of impedance eduction. A local Mach number based on friction velocity is suggested as a way to reduce the inconsistencies found when estimating impedance using upstream and downstream acoustic excitation.

  • 2995.
    Zhou, Lin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Effect of viscosity on impedance eduction and validation2016Inngår i: 21st AIAA/CEAS Aeroacoustics Conference, American Institute of Aeronautics and Astronautics, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Acoustic liners are a key part for reducing aircraft engine noise. Simulation and optimization of liner properties are critically relying on impedance measurement results, so called impedance eduction technology. Traditionally the effect of viscosity has been assumed to have negligible influence. However this paper shows that viscosity has noticeable influence even at low frequencies. The investigation is based on a comparison study using Linearized Euler equations and Linearized Navier-Stokes equations solved by finite element simulations. In the process of impedance eduction a one-dimensional straightforward method is proposed. Normal velocity and displacement have been obtained and discussed. Impedance results are further implemented into a two-dimensional wave propagation code. Finally simulation results have been compared and validated against experimental data.

  • 2996.
    Zhou, Lin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx). KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Effect of viscosity on impedance eduction and validationManuskript (preprint) (Annet vitenskapelig)
  • 2997.
    Zhou, Lin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx). KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Experimental investigation of an in-duct orifice with bias flow under medium and high level acoustic excitation2014Inngår i: International Journal of Spray and Combustion Dynamics, ISSN 1756-8277, Vol. 6, nr 3, s. 267-292Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper experimentally investigates the acoustic properties of an orifice with bias flow under medium and high sound level excitation. Orifices with two different edge configurations were tested. The study includes a wide range of bias flow velocities, various acoustic excitation levels and different frequencies. The nonlinear acoustic scattering matrix was identified by a finely controled two-source method. Aeroacoustic modal analysis was introduced based on eigenvalue-decomposition. Acoustic properties, such as impedance, nonlinear scattering matrix and the eigenvalues were compared and discussed. Experimental results also show that bias flow makes the acoustic properties more complex compared to the no bias flow case, especially when the velocity ratio between acoustic particle velocity and mean flow velocity is near unity.

  • 2998.
    Zhou, Lin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx). KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    The effect of combined high level acoustic excitation and bias flow on the acoustic properties of an in-duct orifice (AIAA 2013-2128)2013Inngår i: 19th AIAA/CEAS Aeroacoustics Conference, American Institute of Aeronautics and Astronautics, 2013, s. 1-13Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper investigates the acoustic properties of an orifice with bias flow under medium and high sound level excitation. Orifices with two different edge configurations were tested experimentally.The study includes a wide range of bias flow velocities, various acoustic excitation levels and different frequencies. The so-called Cummings equation was the starting point for the theoretical modelling. It was modified and a novel orifce acoustic discharge coefficient model was developed both for cases with and without bias flow. The model was experimentally validated. With this model the acoustic resistance is obtained by the harmonic balance method, and the results agree fairly well with the experimental results for low frequencies. Experimental results also show that bias flow makes the acoustic properties much more complex compared to the no bias flow case, especially when the velocity ratio between acoustic particle velocity and mean flow velocity is near unity.  

  • 2999.
    Zhou, Lin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Lahiri, Claus
    Bake, Fredrich
    Enghardt, Lars
    Comparison of impedance eduction results using different methods and test rigs2014Inngår i: 20th AIAA/CEAS Aeroacoustics Conference, 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The last twenty years has seen a large development in inverse techniques for the determination of liner impedance under grazing flow conditions, so called impedance eduction techniques. This paper contribute to a continuing effort to gain confidence in results obtained using different test rigs as well as different impedance eduction techniques. The latter includes the use of different equations for solving for the sound field in the lined section. The DLR reference liner sample HR-S2 studied is a locally reacting single degree of freedom Helmholtz resonator liner which has previously been tested at DLR and NASA Langley. In this study it is tested in a smaller scale facility at KTH, but under similar mean flow and sound pressure level conditions as in the previous studies. A good agreement has been obtained for different method under the same plug flow assumption. The same trend but not identical effects of nonlinearity have been obtained with high levels of acoustic excitation. The effect of different flow Mach number assumptions are discussed in connection with the use of the Ingard-Myers boundary condition.

  • 3000.
    Zhu, Anlin
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Railway Infrastructure Management - System Engineering and Requirement Management2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Rail Control Solutions (RCS) is one division of Bombardier Transportation, aimed at optimising flow of trains. OPTIFLO is a new solution package within RCS, providing services and solutions to address challenges in modern railway infrastructures worldwide. Infrastructure Management (IM) Service is a significant sub-module under OPTIFLO, performing monitoring and diagnostic functionalities for each impacted system or component in railway signalling systems to continuously improve safety, reliability and availability.

    Requirement management is a significant stage while dealing with engineering problems. In this master thesis project, three modules in railway signalling scope are focused, including system level Infrastructure Management, sub-system level Maintenance and Diagnostic Centre (MDC) and sub-system level Remote Sensor Unit (RSU). For each part, requirement managements have been implemented, referring to CENELEC standards where necessary. The work starts with the draft Requirement Specification for IM and then identify the requirements related to diagnostics and performance in each sub-system. Both links between the requirements in different modules and links between the requirements and their test cases are built from the requirement management tool DOORS to realize verification and validation following the system engineering process. Finally, the standard documentations "System Requirement Specification" for each impacted module that are mostly concerned in the thesis have been released.

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