Control of Weak and Strong Reverse-Flow Regions in Incompressible Turbulent Boundary Layers

Fernholz, H. H.; Urzynicok, Frank

doi:10.1007/978-3-540-36085-8_1

Cited by 1 publication

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“…The above relation is also evident while implementing a simple passive flap on the slanted Ahmed body. Figure 14 The quantification of this backflow region is essential to understand the mechanism of drag reduction (Fernholz and Urzynicok 2006). Therefore, the velocity field is shown in Figs.…”

Section: Velocity Analysismentioning

confidence: 99%

A Simple Passive Device for the Drag Reduction of an Ahmed Body

Siddiqui

Chaab

2021

JAFM

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In this paper, a simple passive device is proposed for drag reduction on the 35° Ahmed body. The device is a simple rectangular flap installed at the slant surface of the model to investigate the effect of slant volume, formed between the device and the slant surface, on the flow behaviour. The slant volume can be varied by changing the flap angle. This investigation is performed using the FLUENT software at a Reynolds number of 7.8 × 10 5 based on the height of the model. The SST k-omega model is used to solve the Navier-stokes equations. It is found that this passive device influences the separation bubbles created inside the slant volume and provides a maximum drag reduction of approximately 14% at the flap angle of 10°. Moreover, the device delays the main separation point, which changes the flow conditions at the back of the model. The drag reduction was found to mainly dependent on the suppression of the separation bubbles formed inside the slant volume, which leads to faster pressure recovery. The cause of this pressure recovery is found to be the reduction in recirculation length and width. Also, the addition of a flap reduces the turbulent kinetic energy, which lessened the wake entrainment in the recirculation region, leading to a drag reduction. Also, it hinders the formation of horseshoe vortex that provides a pressure recovery and influence the wake width. However, the investigation also reveals that this device does not reduce the induced drag due to longitudinal vortex from the side edges.

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Section: Velocity Analysismentioning

confidence: 99%