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Particle-laden Turbulent Wall-bounded Flows in Moderately Complex Geometries
KTH, School of Engineering Sciences (SCI), Mechanics, Turbulence.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Wall-bounded turbulent dispersed multiphase flows occur in a variety of industrial, biological and environmental applications. The complex nature of the carrier and the particulate phase is elevated to a higher level when introducing geometrical complexities such as curved walls. Realising such flows and dispersed phases poses challenging problems both from computational and also physical point of view. The present thesis addresses some of these issues by studying a coupled Eulerian–Lagrangian computational framework.

The content of the thesis addresses both turbulent wall flows and coupled particle motion. In the first part, turbulent flow in straight pipes is simulated by means of direct numerical simulation (DNS) with the spectrally accurate code nek5000  to examine the Reynolds-number effect on turbulence statistics. The effect of the curvature to these canonical turbulent pipe flows is then added to generate Prandtl’s secondary motion of first kind. These configurations, as primary complex geometries in this study, are examined by means of statistical analysis to unfold the evolution of turbulence characteristics from a straight pipe. A fundamentally different Prandtl’s secondary motion of the second kind is also put to test by adding side-walls to a canonical turbulent channel flow and analysing the evolution of various statistical quantities with varying the duct width-to-height aspect ratios.

Having obtained a characterisation of the turbulent flow in the geometries of bent pipes and ducts, the dispersion of small heavy particles is modelled in these configurations by means of point particles which are one-way coupled to the flow. For this purpose a parallel Lagrangian Particle Tracking (LPT) scheme is implemented in the spectral-element code nek5000 . Its numerical accuracy, parallel scalability and general performance in realistic situations is scrutinised. The analysis of the resulting particle fields shows that even a small amount of secondary motion has a profound impact on the particle phase dynamics and its concentration maps.

For each of the aforementioned turbulent flow cases new and challenging questions have arisen to be addressed in the present research works. The goal of extending understanding of the particle dispersion in turbulent bent pipes and rectangular ducts are also achieved.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , xii, 71 p.
Series
TRITA-MEK, ISSN 0348-467X ; 2015:09
Keyword [en]
turbulent, complex geometry, particle
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-177310ISBN: 978-91-7595-785-2 (print)OAI: oai:DiVA.org:kth-177310DiVA: diva2:872194
Public defence
2015-12-04, F3, Lindstedtsvägen 26, KTH, Stockholm, 11:01 (English)
Opponent
Supervisors
Funder
Swedish e‐Science Research Center
Note

QC 20151118

Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2015-11-18Bibliographically approved
List of papers
1. Direct Numerical Simulation of Turbulent Pipe Flow at Moderately High Reynolds Numbers
Open this publication in new window or tab >>Direct Numerical Simulation of Turbulent Pipe Flow at Moderately High Reynolds Numbers
Show others...
2013 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 91, no 3, 475-495 p.Article in journal (Refereed) Published
Abstract [en]

Fully resolved direct numerical simulations (DNSs) have been performed with a high-order spectral element method to study the flow of an incompressible viscous fluid in a smooth circular pipe of radius R and axial length 25R in the turbulent flow regime at four different friction Reynolds numbers Re (tau) = 180, 360, 550 and . The new set of data is put into perspective with other simulation data sets, obtained in pipe, channel and boundary layer geometry. In particular, differences between different pipe DNS are highlighted. It turns out that the pressure is the variable which differs the most between pipes, channels and boundary layers, leading to significantly different mean and pressure fluctuations, potentially linked to a stronger wake region. In the buffer layer, the variation with Reynolds number of the inner peak of axial velocity fluctuation intensity is similar between channel and boundary layer flows, but lower for the pipe, while the inner peak of the pressure fluctuations show negligible differences between pipe and channel flows but is clearly lower than that for the boundary layer, which is the same behaviour as for the fluctuating wall shear stress. Finally, turbulent kinetic energy budgets are almost indistinguishable between the canonical flows close to the wall (up to y (+) a parts per thousand aEuro parts per thousand 100), while substantial differences are observed in production and dissipation in the outer layer. A clear Reynolds number dependency is documented for the three flow configurations.

Keyword
Wall turbulence, Pipes, Channels, Boundary layers, Direct numerical simulation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-133634 (URN)10.1007/s10494-013-9482-8 (DOI)000325612100004 ()2-s2.0-84885953214 (Scopus ID)
Funder
Swedish Research Council, 2010 - 4147 2010 - 6965
Note

QC 20131111

Available from: 2013-11-11 Created: 2013-11-08 Last updated: 2017-12-06Bibliographically approved
2. Evolution of turbulence characteristics from straight to curved pipes
Open this publication in new window or tab >>Evolution of turbulence characteristics from straight to curved pipes
2013 (English)In: International Journal of Heat and Fluid Flow, ISSN 0142-727X, E-ISSN 1879-2278, Vol. 41, no SI, 16-26 p.Article in journal (Refereed) Published
Abstract [en]

Fully developed, statistically steady turbulent flow in straight and curved pipes at moderate Reynolds numbers is studied in detail using direct numerical simulations (DNS) based on a spectral element discretisation. After the validation of data and setup against existing DNS results, a comparative study of turbulent characteristics at different bulk Reynolds numbers Re-b = 5300 and 11,700, and various curvature parameters kappa = 0, 0.01, 0.1 is presented. In particular, complete Reynolds-stress budgets are reported for the first time. Instantaneous visualisations reveal partial relaminarisation along the inner surface of the curved pipe at the highest curvature, whereas developed turbulence is always maintained at the outer side. The mean flow shows asymmetry in the axial velocity profile and distinct Dean vortices as secondary motions. For strong curvature a distinct bulge appears close to the pipe centre, which has previously been observed in laminar and transitional curved pipes at lower Re-b only. On the other hand, mild curvature allows the interesting observation of a friction factor which is lower than in a straight pipe for the same flow rate. All statistical data, including mean profile, fluctuations and the Reynolds-stress budgets, is available for development and validation of turbulence models in curved geometries.

Place, publisher, year, edition, pages
Elsevier, 2013
Keyword
Wall turbulence, Pipe flow, Curvature effects, Reynolds-stress budgets, Coiled tube
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-124983 (URN)10.1016/j.ijheatfluidflow.2013.03.005 (DOI)000321078700003 ()2-s2.0-84878568406 (Scopus ID)
Conference
9th International Symposium on Engineering Turbulence Modelling and Measurements (ETMM), JUN 06-08, 2012, Thessaloniki, Greece
Funder
Swedish e‐Science Research Center
Note

QC 20130805

Available from: 2013-08-05 Created: 2013-08-02 Last updated: 2017-12-06Bibliographically approved
3. Evidence of sublaminar drag naturally occurring in a curved pipe
Open this publication in new window or tab >>Evidence of sublaminar drag naturally occurring in a curved pipe
2015 (English)In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 27, no 3, 035105Article in journal (Refereed) Published
Abstract [en]

Steady and unsteady flows in a mildly curved pipe for a wide range of Reynolds numbers are examined with direct numerical simulation. It is shown that in a range of Reynolds numbers in the vicinity of Re-b approximate to 3400, based on bulk velocity and pipe diameter, a marginally turbulent flow is established in which the friction drag naturally reduces below the laminar solution at the same Reynolds number. The obtained values for friction drag for the laminar and turbulent (sublaminar) flows turn out to be in excellent agreement with experimental measurements in the literature. Our results are also in agreement with Fukagata et al. ["On the lower bound of net driving power in controlled duct flows," Phys. D 238, 1082 (2009)], as the lower bound of net power required to drive the flow, i.e., the pressure drop of the Stokes solution, is still lower than our marginally turbulent flow. A large-scale traveling structure that is thought to be responsible for that behaviour is identified in the instantaneous field. This mode could also be extracted using proper orthogonal decomposition. The effect of this mode is to redistribute the mean flow in the circular cross section which leads to lower gradients at the wall compared to the laminar flow.

Keyword
Channel Flow, Turbulence, Transition, Laminar, Power
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-166347 (URN)10.1063/1.4913850 (DOI)000352309400044 ()2-s2.0-84924943480 (Scopus ID)
Funder
Swedish e‐Science Research Center
Note

QC 201505

Available from: 2015-05-11 Created: 2015-05-07 Last updated: 2017-12-04Bibliographically approved
4. Swirl-switching phenomenon in turbulent flow through toroidal pipes
Open this publication in new window or tab >>Swirl-switching phenomenon in turbulent flow through toroidal pipes
(English)Manuscript (preprint) (Other academic)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-177303 (URN)
Note

QS 2015

Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2015-11-18Bibliographically approved
5. Particle transport in turbulent curved pipe flow
Open this publication in new window or tab >>Particle transport in turbulent curved pipe flow
(English)Manuscript (preprint) (Other academic)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-177305 (URN)
Note

QS 2015

Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2015-11-18Bibliographically approved
6. Particle Velocity and Acceleration in Turbulent Bent Pipe Flows
Open this publication in new window or tab >>Particle Velocity and Acceleration in Turbulent Bent Pipe Flows
2015 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 95, no 2-3, 539-559 p.Article in journal (Refereed) Published
Abstract [en]

We study the dynamics of dilute micro-size inertial particles in turbulent curved pipe flows of different curvature by means of direct numerical simulations with one-way coupled Lagrangian particle tracking. The focus of this work is on the first and second order moments of the velocity and acceleration of the particulate phase, relevant statistics for any modelling effort, whereas the particle distribution is analysed in a previous companion paper. The aim is to understand the role of the cross-stream secondary motions (Dean vortices) on the particle dynamics. We identify the mean Dean vortices associated to the motion of the particles and show that these are moved towards the side-walls and, interestingly, more intense than those of the mean flow. Analysis of the streamwise particle flux reveals a substantial increase due to the secondary motions that brings particles towards the pipe core while moving them towards the outer bend. The in-plane particle flux, most intense in the flow viscous sub-layer along the side walls, increases with particle inertia and pipe curvature. The particle reflections at the outer bend, previously observed also in other strongly curved configurations, locally alter the particle axial and wall-normal velocity and increase turbulent kinetic energy.

Place, publisher, year, edition, pages
[Noorani, Azad; Brandt, Luca; Schlatter, Philipp] Royal Inst Technol, Linne FLOW Ctr, KTH Mech, SE-10044 Stockholm, Sweden. [Noorani, Azad; Brandt, Luca; Schlatter, Philipp] Royal Inst Technol, KTH Mech, Swedish E Sci Res Ctr SeRC, SE-10044 Stockholm, Sweden. [Sardina, Gaetano] Univ Stockholm, Dept Meteorol, S-10691 Stockholm, Sweden.: , 2015
Keyword
Curvature effect, Particulate dispersion, Secondary motion, Gas-solid flow, Bent pipe, Particle transport
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-176348 (URN)10.1007/s10494-015-9638-9 (DOI)000362364500018 ()2-s2.0-84947868160 (Scopus ID)
Note

QC 20151106

Available from: 2015-11-06 Created: 2015-11-03 Last updated: 2017-12-01Bibliographically approved
7. Aspect ratio effects in turbulent duct flows studied through direct numerical simulation
Open this publication in new window or tab >>Aspect ratio effects in turbulent duct flows studied through direct numerical simulation
Show others...
2014 (English)In: Journal of turbulence, ISSN 1468-5248, E-ISSN 1468-5248, Vol. 15, no 10, 677-706 p.Article in journal (Refereed) Published
Abstract [en]

Three-dimensional effects in turbulent duct flows, i.e., sidewall boundary layers and secondary motions, are studied by means of direct numerical simulation (DNS). The spectral element code Nek5000 is used to compute turbulent duct flows with aspect ratios 1-7 (at Re-b,Re- c = 2800, Re-tau,Re- c similar or equal to 180) and aspect ratio 1 (at Re-b,Re- c = 5600, Re-tau,Re- c similar or equal to 330), in streamwise-periodic boxes of length 25h. The total number of grid points ranges from 28 to 145 million, and the pressure gradient is adjusted iteratively in order to keep the same bulk Reynolds number in the centreplane with changing aspect ratio. Turbulence is initiated via a trip forcing active during the initial stages of the simulation, and the statistical convergence of the data is discussed both in terms of transient approach and averaging period. Spanwise variations in wall shear, mean-flow profiles, and turbulence statistics are analysed as a function of aspect ratio, and also compared with the spanwise-periodic channel (as idealisation of an infinite aspect ratio duct). The computations show good agreement with experimental measurements carried out in parallel at the Illinois Institute of Technology (IIT) in Chicago, and highlight the relevance of sidewall boundary layers and secondary vortices in the physics of the duct flow. The rich array of secondary vortices extending throughout the upper and lower walls of the duct, and their dependence on Reynolds number and aspect ratio, had not been reported in the literature before.

Keyword
direct numerical simulation, secondary motions, secondary vortices/motions, three-dimensional flows, turbulent duct flow, wall turbulence
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-141942 (URN)10.1080/14685248.2014.925623 (DOI)000340121000003 ()2-s2.0-84904987697 (Scopus ID)
Note

Updated from manuscript to article in journal.

QC 20140908

Available from: 2014-02-26 Created: 2014-02-26 Last updated: 2017-12-05Bibliographically approved
8. Aspect-ratio effect on particle transport in turbulent duct flows
Open this publication in new window or tab >>Aspect-ratio effect on particle transport in turbulent duct flows
(English)Manuscript (preprint) (Other academic)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-177307 (URN)
Note

QS 2015

Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2015-11-18Bibliographically approved
9. Informal introduction to program structure of spectral interpolation in nek5000
Open this publication in new window or tab >>Informal introduction to program structure of spectral interpolation in nek5000
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The algorithm of the interpolation implementation in the spectral element codenek5000is documented informally. The original code is written by James Lottes at Argonne National Laboratories. The various steps of the operations are generally described and visualised for a typical deformed mesh. The corresponding routines and their argument lists for each stage of the interpolation are also explained. The memory structure of the implementation is briefly discussed. Finally, the code overview of the routines is presented.

National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-177308 (URN)
Note

QS 2015

Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2015-11-18Bibliographically approved

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