PIV analysis of wake characteristics of slanted-back Ahmed bodies: effect of leading-edge shape

Abstract

This study experimentally investigates turbulent flow separation around a slanted-back Ahmed body with different leading edge configurations [rounded (RL) and square (SL)] using the particle image velocimetry technique. The Reynolds number (based on freestream velocity and body height) is \({\text{Re}}_{\text{H}}\) = 0.17 × 10⁵. Spatiotemporal flow characteristics, including mean flow, vorticity flux, two-point correlation, reverse flow area, frequency spectra, and proper orthogonal decomposition, are analyzed to elucidate the effects of leading edge shape on separated shear layer interactions over the roof, slanted surface, and the wake region. The results show that rounding the leading edge of the Ahmed body leads to the formation of smaller coherent structures with lower shedding frequency over the roof. While, the structures are still smaller over the slanted surface and the wake region of the RL body, the shedding frequency surpasses that of the SL ones. The results also show evidence of the identical shedding frequency over the roof, slanted surface, and wake region of the RL body. Detailed analyses, including convective velocities of vortices over the roof, slanted surface, and in the wake region, vary significantly between SL and RL cases, indicating distinct shedding mechanisms influenced by leading edge geometry.