Abstract
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.
Highlights
In recent years, the aerodynamic drag performance of an automobile has become more important for its fuel efficiency because the efficiency of the powertrain has rapidly been improved through hybridization, electrification, and the improvement of combustion technology
It the fluid-dynamic forces and moment measured in a circular motion test (CMT) of the model with θ = 35 at ω’ = 0.067
The fluid-dynamic forces acting on the Ahmed models with θ = 25° and θ = 35° under a uniform crosswind condition crosswind condition were were reproduced reproducedby bythe theSCW
Summary
The aerodynamic drag performance of an automobile has become more important for its fuel efficiency because the efficiency of the powertrain has rapidly been improved through hybridization, electrification, and the improvement of combustion technology. In the conventional development process of vehicle aerodynamics, a vehicle subjected to a steady and uniform airflow in a wind tunnel or numerical simulation has been considered. This condition assumes a relative airflow acting on a vehicle running at a constant speed and a steady posture in stationary air. The changes in the relative wind direction caused by on-road disturbance and their effects have been investigated using the so-called yaw condition or steady crosswind method [1], in which a real automobile [2] or an experimental vehicle model [3,4,5] is placed at a steady yaw angle with respect to a uniform flow.
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