Drag Reduction of a Simple Bluff Body by Changing The Rear End

• The flow field around bluff bodies constitutes a classic areawithin fluid dynamics and has been the topic for much researchthrough the years. However, in the use for road vehicles withthe effect of the ground, the behavior is changed very muchfrom more classical aviation usage. In this paper we areinvestigating the drag force reduction on a vehicle likesimplified model with rear open diffuser when stationaryground simulation is considered.The objective with this work was to study the rear end of abluff body and optimize it for drag with ground vehicle likeboundaries. Here the testing contains two common bodyvariants, square back, boat tailed/fastback in generic forms.Scale model testing combined with simulations is used toexplain behavior and flow field. The model testing isperformed in the L2 scale model wind tunnel at ChalmersUniversity of Technology in Gothenburg, Sweden. Simulationsare done with the commercial CFD code Fluent.A diffuser on a car is normally used to create down forcebut here it is tested to see if the energy in the flow can be usedto optimize reduction of drag. One part of the study is to showthe potential in optimizing the rear end underbody for drag, byvarying the diffuser angle.The results show a potential in drag reduction by using adiffuser and varying effect depending on other rear endgeometries.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Strömningsmekanik och akustik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Fluid Mechanics and Acoustics (hsv//eng)

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