Quantitative Representations of Aerodynamic Effects on Handling Response and Flat Ride of Vehicles

Ogawa, Atsushi; Mashio, Susumu; Yano, Shujiro; Kawamura, Tetsuhiro

doi:10.4271/2012-01-0445

Cited by 23 publications

(6 citation statements)

References 8 publications

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“…The dynamic effect of pitching oscillation is considered to appear only at the center area. This effect is considered to be due to the change in the relative angle of attack and the dynamic camber effect, which was indicated by Ogawa et al (2012). The flow around the underside appears to be convex about the oscillation center due to the dynamic camber effect during the downward pitching motion.…”

Section: Pitching Testmentioning

confidence: 96%

Effects of heaving and pitching motions on underside aerodynamics of a sedan vehicle

Maruyama

Shinji

Nonomura

et al. 2019

JFST

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Unsteady pressure distributions around a simplified sedan automobile model were investigated by conducting dynamic wind-tunnel testing using the newly developed forced oscillating apparatus, HEXA-X3, which can produce 6-degrees-of-freedom motion. The effects of heaving and pitching oscillation were investigated as the model simulated a vehicle running on a flat road at approximately 40 m/s and 1 Hz oscillation. The effects of the ground plate on unsteady pressure distributions over the model surfaces were measured while simulating heaving and pitching motion at Strouhal-number conditions similar to those for actual vehicles. The influence of the tubing on the frequency response of the pressure sensor was evaluated to be negligible by conducting a calibration experiment first. In the static case, the overall pressure distribution was consistent with that for a typical sedan, and the influence of the local relative flow velocity changes due to the contraction effect was observed in the underside of the model. In the forced oscillation tests, the effect of heaving and pitching motions on the flow around the underside was investigated. Effects of oscillation parameters, specifically amplitude and frequency, were investigated using the gain and phase-lag normalized by data from the steady model. Results of the test indicate that there is a characteristic distribution in pressure fluctuation, and the phenomena that become dominant in the flow around the underside vary according to location. The dynamic heaving motion was shown to change the pressure distribution, possibly due to changes in the effective angle of attack in addition to the static effect. The pitching test showed that a dynamic camber effect works in addition to those effects.

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Section: Pitching Testmentioning

confidence: 96%

Effects of heaving and pitching motions on underside aerodynamics of a sedan vehicle

Maruyama

Shinji

Nonomura

et al. 2019

JFST

View full text Add to dashboard Cite

show abstract

“…Recently, the effects of these aerodynamic characteristics on vehicle motion have also been investigated. Ogawa et al 1 measured aerodynamic forces and their dependences on a vehicle attitude. They suggested a method for representing the aerodynamic effects on maneuverability and the flat ride that uses an equivalent front-rear lift force.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Mode Decomposition of Flow around a Full-Scale Road Vehicle using Unsteady CFD

Ikeda

Matsumoto

Tsubokura

et al. 2016

34th AIAA Applied Aerodynamics Conference

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The unsteady aerodynamic forces and flow structure around a full-scale road vehicle were investigated in this study. Special focus was given to the fluctuating lift force acting on the vehicle. It was proposed that the fluctuating lift force, especially at frequencies less than 5 Hz, affects the directional stability and the feel of the ride, because this frequency range is close to the natural frequency of the vehicle's mechanical system. The objectives were to clarify the flow structures that cause the low-frequency fluctuation of the lift force by using a mode decomposition technique and to suggest a method for improving the vehicle's aerodynamic stability. The target model was a full-scale production vehicle. The model had a complicated geometry based on available CAD data, so that the engine compartment and complicated underbody geometry were reproduced. An unsteady CFD technique was applied to obtain the transient aerodynamic forces and snapshots of the flow structure around the vehicle. Dynamic mode decomposition was used to extract the fluctuating flow features at a specific frequency. The results indicated that the lift force acting on the trunk deck and rear underbody contributed to the low-frequency fluctuating lift force. NomenclatureA = frontal area of the vehicle (= 2.189 m 2 ) CSGS = model constant of Smagorinsky model CD = drag coefficient (= 2Fx /ρu 2 A) CL = lift coefficient (= 2Fz /ρu 2 A) CLF, CLR = lift coefficient acting on the front wheel and the rear wheel 2 fd= Van-Driest-type function Fx, Fy = drag force and lift force acting on the vehicle i, j, k = directions of spatial coordinate p = static pressure Sij = strain rate tensor ui = velocity for i-th direction uτ = friction velocity on the solid wall y + = non-dimensional distance from the wall (= yp uτ/ν) Δ = spatial filter length (cube root of the numerical element volume) ν = kinetic viscosity ρ = density of the incoming fluid

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“…Due to the higher density of water, relatively larger fluid-dynamic force acts on the same length-scale model in the similar flow field, allowing for more accurate measurements. Therefore, some towing tank tests on automobile aerodynamics [22][23][24][25] have already been reported. When moving ground systems were not standard in automobile aerodynamics measurement, some studies on the ground effect of automobile aerodynamics have been conducted in a towing tank, taking the advantage of not requiring the Galilean transformation.…”

Section: Introductionmentioning

confidence: 99%

“…Aoki et al [24] conducted towing tests of a one-fifth-scale sedan-type automobile model in a ship model basin to measure the fluid-dynamic force and surface pressure acting on the automobile model under the ground effect, and to visualize the flow around the vehicle. Towing tank tests have also been used to measure the fluid-dynamic responses of automobile models with pitching motion [25]. Because the density of the experimental model can easily be close to the density of water, the inertial force due to the model acceleration becomes relatively smaller than that during wind tunnel measurements.…”

Section: Introductionmentioning

confidence: 99%

Fluid-Dynamic Force Measurement of Ahmed Model in Steady-State Cornering

et al. 2020

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The effects of on-road disturbances on the aerodynamic drag are attracting attention in order to accurately evaluate the fuel efficiency of an automobile on a road. The present study investigated the effects of cornering motion on automobile aerodynamics, especially focusing on the aerodynamic drag. Using a towing tank facility, measurements of the fluid-dynamic force acting on Ahmed models during steady-state cornering were conducted in water. The investigation included Ahmed models with slant angles θ = 25° and 35°, reproducing the wake structures of two different types of automobiles. The drag increase due to steady-state cornering motion was experimentally measured, and showed good agreement with previous numerical research, with the measurements conducted at a Reynolds number of 6 × 105, based on the model length. The Ahmed model with θ = 35° showed a greater drag increase due to the steady-state cornering motion than that with θ = 25°, and it reached 15% of the total drag at a corner with a radius that was 10 times the vehicle length. The results indicated that the effect of the cornering motion on the automobile aerodynamics would be more important, depending on the type of automobile and its wake characteristics.

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Quantitative Representations of Aerodynamic Effects on Handling Response and Flat Ride of Vehicles

Cited by 23 publications

References 8 publications

Effects of heaving and pitching motions on underside aerodynamics of a sedan vehicle

Effects of heaving and pitching motions on underside aerodynamics of a sedan vehicle

Dynamic Mode Decomposition of Flow around a Full-Scale Road Vehicle using Unsteady CFD

Fluid-Dynamic Force Measurement of Ahmed Model in Steady-State Cornering

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