Aerodynamic performance of several passive vortex generator configurations on an Ahmed body subjected to yaw angles
H. Viswanathan
Abstract
Abstract We evaluate the aerodynamic performance of several passive vortex generators (VGs) placed on a standard Ahmed body, with a slant angle ( α = 35º), subjected to different yawing angles ( β ) using RANS-based models. Rigorous validation of the numerical results is performed with previously published experimental data for ( β ≤ 8º) for the Ahmed body. Our model results depict a good overall agreement with several experimental data sets. An array of different vortex generators such as the delta-winglet (DVGs), the cylindrical (CVGs) and trapezoidal (TVGs) types are introduced on to the validated model. The introduction of CVGs and DVGs tends to have a beneficial aerodynamic performance for ( β = 0º). In contrast, the TVGs tend to impair the performance by producing massive flow separation over the slant for ( β = 0º). Conversely, for ( β > 0º), a swift transition happens with TVGs wherein the high-energy streamwise vortices that are produced tend to improve the pressure footprint, thereby reducing the overall drag. A deterioration in the performance of DVGs is predicted during ( β > 4º), wherein the ‘c’-pillar vortex on the leeward side interferes with the streamwise vortical structure, which adversely influences the flow over the roof-slant edge. Overall, a maximum of ~ 8.5% and ~ 7.7% drag reduction appears to be possible with the designed CVGs and TVGs at smaller vehicle yawing conditions.