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The effects of oscillatory boat-tail flaps on the near wake of a prototypical heavy vehicle
2010 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In the society of today, with the global warming as a major issue in both political and economical decisions, the fuel efficiency of vehicles has become an area of increased research. This has lead to more efficient engines and well thought-out designs to reduce the fuel consumption and therefore also the carbon footprint left by them. This study concentrates on the aerodynamics of a truck / trailer combination and in more specifics, the near wake arising behind the trailer. Since a truck / trailer combination is subjected to certain geometry constrains to maximize the volume of cargo carried, the possibilities of changing the general design is limited. Instead the focus has been to develop different add-ons to change the aerodynamic properties in a favourable way. Experiments have been conducted on a model of a trailer to study the possible changes in its near wake behind the trailer. The model was fitted with vertical flaps on both sides of the back plate, which were set to oscillate at given frequencies and amplitudes. Experiments were carried out using an in-house developed PIV setup in a water channel at the Department of Mechanical and Aerospace Engineering at Monash University. The oscillation of the flaps perturbed the flow in such a way that the shear layer was significantly changed and the roll up of vortices was moved further upstream, causing a rise in the rate of entrainment and a shorter reattachment length. It also had the effect of a reduced wake size and higher velocities within the wake. These are all effects that are consistent with an increase in the base pressure at the back plate of the trailer and therefore also a reduced drag coefficient, as they are strongly related.

Place, publisher, year, edition, pages
Keyword [en]
Physics Chemistry Maths, Truck-trailer aerodynamics, particle image velocimetry, fluid, dynamics
Keyword [sv]
Fysik, Kemi, Matematik
URN: urn:nbn:se:ltu:diva-46471ISRN: LTU-EX--10/081--SELocal ID: 41bd4683-ce44-4406-b0ef-ffb6cd67a6d4OAI: diva2:1019785
Subject / course
Student thesis, at least 30 credits
Educational program
Engineering Physics, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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