Drag reduction mechanisms on a generic square-back vehicle using an optimised yaw-insensitive base cavity

Abstract Regulations on global greenhouse gas emission are driving the development of more energy-efficient passenger vehicles. One key factors influencing energy consumption is aerodynamic drag where a large portion associated with base wake. Environmental conditions such as wind can increase separated flow. This paper investigates an optimised yaw-insensitive cavity square-back vehicle in steady crosswind. The test object simplified model scale bluff body, Windsor geometry, wheels. tested experimentally straight and tapered cavity. taper angles have been numerically to improve robustness side relation drag. Base pressures tomographic Particle Image Velocimetry full wake were measured tunnel. results indicate that decreases crossflow within wake, increasing pressure, therefore lowering additional tapering further reduces smaller less losses. overall unsteadiness reduced by minimising mixing shear layers well dampening motion. However, coherent motions, indicative balanced increased investigated cavities. Graphical abstract