Experimental Study on the Influence of Model Motion on the Aerodynamic Performance of a Race Car

Aschwanden, Peter; Müller, Jürg; Knörnschild, Ulrich

doi:10.4271/2006-01-0803

Cited by 20 publications

(16 citation statements)

References 3 publications

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“…Other research carried out on side force and yaw moment (e.g., Tsubokura et al, 2010;Mansor and Passmore, 2007;Macklin et al, 1997;Ryan and Dominy, 1998) has also indicated the incomplete representation of a real transient situation by a steady-state values. Regarding lift coefficient under the influence of ride-height fluctuation, such as that during heaving or pitching, Aschwanden et al (2006) reported a significant difference in wind-tunnel measurements of a race-car model obtained through steadystate and transient approaches. Moreover, a recent road-test result by Okada et al (2009) indicates that the straightahead stability behaviors of vehicles with close drag and lift coefficients (differences of only 6.5 and 22.2%, respectively) vary, as shown by their differences in rear-ride height fluctuation and straight-ahead stability sensory ratings.…”

Section: Introductionmentioning

confidence: 99%

Numerical quantification of aerodynamic damping on pitching of vehicle-inspired bluff body

Cheng¹,

Tsubokura²,

Nakashima³

et al. 2012

Journal of Fluids and Structures

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The influence of transient flows on vehicle stability was investigated by large eddy simulation. To consider the dynamic response of a vehicle to real-life transient aerodynamics, a dimensionless parameter that quantifies the amount of aerodynamic damping for vehicle subjects to pitching oscillation is proposed. Two vehicle models with different stability characteristics were created to verify the parameter. For idealized notchback models, underbody has the highest contribution to the total aerodynamic damping, which was up to 69%. However, the difference between the aerodynamic damping of models with distinct A-and C-pillar configurations mainly depends on the trunk-deck contribution. Comparison between dynamically obtained phase-averaged pitching moment with quasisteady values shows totally different aerodynamic behaviors.

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Section: Introductionmentioning

confidence: 99%

Numerical quantification of aerodynamic damping on pitching of vehicle-inspired bluff body

Cheng¹,

Tsubokura²,

Nakashima³

et al. 2012

Journal of Fluids and Structures

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“…Howell and Le Good, 1999;Okada et al, 2009) or wind tunnel measurement (e.g. Aschwanden et al, 2006). The applicability of the methods is bounded by their inherent limitations.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic stability of road vehicles in dynamic pitching motion

Cheng

Tsubokura

Okada

et al. 2013

Journal of Wind Engineering and Industrial Aerodynamics

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The main object of the present study is to investigate numerically the mechanism of aerodynamic damping of pitching oscillation in sedan-type vehicles. The transient numerical solver employed is based on the Large Eddy Simulation (LES) method. Whilst, the Arbitrary Lagrangian-Eulerian (ALE) method was used to realize the vehicle motion during dynamic pitching and fluid flow coupled simulations. Validation of the numerical method was done by comparing the flow structures obtained from the LES to the corresponding flow structures observed in the wind tunnel measurements. Two vehicle models with basic sedan-type automobile shape were created to study the influences of upper body geometry on the aerodynamic pitching stability of sedan-type vehicle. In addition, the credibility of modeling of automotive aerodynamics by simple bluff body models was verified. For the sedan-type models investigated, the trailing vortices that shed from the A-pillar and C-pillar edges were found to produce the opposite tendencies on how they affect the aerodynamic pitching stability of the models. In particular, the vortex shed from the A-pillar edge tended to enhance the pitching oscillation, while the vortex shed from the C-pillar edge tended to suppress it. Hence, the vehicle with rounded A-pillar and angular C-pillar exhibited a higher aerodynamic damping than the vehicle with the opposite A-and C-pillars configurations. The aerodynamic damping mechanism has been proposed based on the results of flow visualization on the phase-averaged flow properties.

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“…These methods have produced inconsistent results, in some case showing aerodynamic coefficients measured under transient conditions to be larger than those measured on a static model and in others the same or smaller. Within these results is evidence of flow field hysteresis, Guilmineau and Chometon [9], and hysteresis has also been found in the lift and pitching moment coefficients recording during pitching and heaving oscillations by Aschwanden et al [10] and also Nakashima et al [11]. Unsteady crosswind tests also show periodic features within the flow field altering due to the unsteady onset wind, Schröck et al [12] and different response times from different flow structures around the vehicle, [5].…”

Section: Introductionmentioning

confidence: 69%

Unsteady Aerodynamics of an Oscillating Fastback Model

Fuller¹,

Passmore²

2013

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

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This paper investigates the surface pressures found on the sides of a Davis model under steady state conditions and during yawed oscillations at a reduced frequency which would generally be assumed to give a quasi-static response. The surface pressures are used to investigate the flow field and integrated to infer aerodynamic loads. The results show hysteresis in the oscillating model's results, most strongly in the A-pillar flows. The changes to the flow field reduce strength of the flows around the rear pillars, reduce the strength and extent of the A-pillar vortex and cause the surface pressures to couple with the oscillating motion. This work shows the flows around the front of a vehicle may be more important to a vehicle's unsteady aerodynamics than is generally accepted and also leads to the conclusions that the reduced frequency parameter may not fully describe the onset unsteadiness.

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Experimental Study on the Influence of Model Motion on the Aerodynamic Performance of a Race Car

Cited by 20 publications

References 3 publications

Numerical quantification of aerodynamic damping on pitching of vehicle-inspired bluff body

Numerical quantification of aerodynamic damping on pitching of vehicle-inspired bluff body

Aerodynamic stability of road vehicles in dynamic pitching motion

Unsteady Aerodynamics of an Oscillating Fastback Model

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