Aerodynamic Drag Reduction on a Simple Car-Like Shape with Rear Upper Body Taper

Howell, Jeff; Passmore, Martin A.; Tuplin, Simon

doi:10.4271/2013-01-0462

Cited by 32 publications

(20 citation statements)

References 14 publications

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“…The downwash created by the top slanted surface, indeed, leads to a shift of the region with the highest values of C P rms (associated with bi-stability) towards the bottom trailing edge, with the appearance of three zones of low unsteadiness close to the top edge of the base. In particular, the first two regions are placed close to the tips of the taper, in the same zones where the longitudinal trailing vortices created by the slant (as already shown by the PIV results obtained by Howell et al in [28] for a similar configuration) are expected to interact with the near wake recirculation. The third region of low unsteadiness, is positioned close to the middle of the taper trailing edge, where the amount of flow deflected by the taper into the model wake reaches its maximum.…”

Section: Top Tapermentioning

confidence: 52%

Influence of Short Rear End Tapers on the Unsteady Base Pressure of a Simplified Ground Vehicle

Pavia¹,

Passmore²,

Gaylard³

2016

SAE Technical Paper Series

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Section: Top Tapermentioning

confidence: 52%

Influence of Short Rear End Tapers on the Unsteady Base Pressure of a Simplified Ground Vehicle

Pavia¹,

Passmore²,

Gaylard³

2016

SAE Technical Paper Series

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“…Howell et al [25] showed, using the Windsor geometry but as here applying the tapering only to the upper half of the body, that the introduction of a shoulder into the geometry leads to the formation of a vortex which, in turn, generates downwash. This mechanism is likely to be present for the SUV with the streamwise vortices from the shoulder producing a downwash and an inwash resulting in a recirculation in the upper region of the base (low pressure and low fluctuations) and a downwash dominated wake.…”

Section: Side Tapersmentioning

confidence: 99%

The Effect of Passive Base Ventilation on the Aerodynamic Drag of a Generic SUV Vehicle

Varney¹,

Passmore²,

Gaylard³

2017

SAE Int. J. Passeng. Cars - Mech. Syst.

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INTRODUCTIONAerodynamic drag is an increasing concern for vehicle manufacturers due to its impact on CO 2 emissions and fuel economy. For instance, the European Union will phase in significant penalties for CO 2 emissions above a mass-dependent limit curve from 2020 [1]. As Sport Utility Vehicles (SUVs) are the most popular body type [2], the methods of reducing their drag come under closer scrutiny, specifically when the success of these vehicles owes much to elements of design and utility.The blunt nature of SUV rear geometries arises from their historical use as working vehicles, with a need for maximal access to a large rear load space, whilst maintaining off-road capability. For squareback geometries, such as these, more than one-third of the aerodynamic drag is attributable to the rear surfaces [3], resulting from separation at the trailing edges leading to low pressure on the base.In order to combat the depressed static pressure on the base of vehicles a number of studies have been done to investigate base pressure recovery. Typical passive methods such as side tapering [4,5], roof tapering [4,6,7,8,9], roughness strips [10] and underbody tapering [11,12] have all been shown to result in base drag reductions.Active methods have also been tested with drag reductions being reported but little shown in terms of net energy reduction (as the systems require energy input); these include rolling trailing and leading edges [13], blowing [14] and thermal riblets [15].Both passive and active methods alter the shear layers bounding the wake of the vehicle and, as a result change the base pressure and reduce drag. Typically the reduction in drag is shown to be due to the increase in base pressure [4,5,7,8] Adrian Gaylard Jaguar Land Rover ABSTRACT Sports Utility Vehicles (SUVs) typically have a blunt rear end shape (for design and practicality), however this is not beneficial for aerodynamic drag. Drag can be reduced by a number of passive and active methods such as tapering and blowing into the base. In an effort to combine these effects and to reduce the drag of a visually square geometry slots have been introduced in the upper side and roof trailing edges of a squareback geometry, to take air from the freestream and passively injects it into the base of the vehicle to effectively create a tapered body.This investigation has been conducted in the Loughborough University's Large Wind Tunnel with the ¼ scale generic SUV model. The basic aerodynamic effect of a range of body tapers and straight slots have been assessed for 0° yaw. This includes force and pressure measurements for most configurations. The slots generate useful, but small, drag reductions with the best configurations giving reductions in drag coefficient (C d ) of approximately 0.01, whereas the best taper configurations reduce C d by close to 0.035. The slots also have a tendency to modify the lift.

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“…The details of this model have been well documented previously (see, for example [7], [17] and [18]). The model is 1.044m long, 0.389m wide and 0.289m high.…”

Section: Physical Modelmentioning

confidence: 87%

Experimental and Computational Study of Vehicle Surface Contamination on a Generic Bluff Body

Kabanovs¹,

Varney²,

Garmory³

et al. 2016

SAE Technical Paper Series

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This paper focuses on methods used to model vehicle surface contamination arising as a result of rear wake aerodynamics. Besides being unsightly, contamination, such as self-soiling from rear tyre spray, can degrade the performance of lighting, rear view cameras and obstruct visibility through windows. In order to accurately predict likely contamination patterns, it is necessary to consider the aerodynamics and multiphase spray processes together. This paper presents an experimental and numerical (CFD) investigation of the phenomenon.The experimental study investigates contamination with controlled conditions in a wind tunnel using a generic bluff body (the Windsor model.) Contamination is represented by a water spray located beneath the rear of the vehicle. The aim is to investigate the fundamentals of contamination in a case where both flow field and contamination patterns can be measured, and also to provide validation of modelling techniques in a case where flow and spray conditions are known.CFD results were obtained using both steady RANS and unsteady URANS solvers, combined with particle tracking methods. Steady RANS does not capture the wake structures accurately and this affects the contamination prediction. URANS is able to recover the large-scale wake unsteadiness seen in the experimental data, but the difference between the experimental and computational contamination distributions is still notable. The CFD is also able to provide further insight by showing the behaviour of particles of different sizes. Large particles are found to take on a ballistic trajectory and penetrate the wake. In contrast, small particles are shown to be less likely to become entrained into the wake.

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Aerodynamic Drag Reduction on a Simple Car-Like Shape with Rear Upper Body Taper

Cited by 32 publications

References 14 publications

Influence of Short Rear End Tapers on the Unsteady Base Pressure of a Simplified Ground Vehicle

Influence of Short Rear End Tapers on the Unsteady Base Pressure of a Simplified Ground Vehicle

The Effect of Passive Base Ventilation on the Aerodynamic Drag of a Generic SUV Vehicle

Experimental and Computational Study of Vehicle Surface Contamination on a Generic Bluff Body

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