PIV Analysis of Wake Characteristics of Slanted-Back Ahmed Bodies: Effect of Leading-Edge Shape

Abstract

This study experimentally investigates turbulent flow separation over a slanted-back Ahmed body with different leading-edge configurations (rounded and square) using the particle image velocimetry (PIV) technique. Reynolds number (based on free-stream velocity and body height) is \({\text{Re}}_{\text{H}}\) = 0.17 × 105. Spatiotemporal flow characteristics, including mean flow, vorticity flux, spatial two-point correlation, reverse flow area, turbulent kinetic energy budget, frequency spectra, and proper orthogonal decomposition (POD) are analyzed. The results reveal a larger recirculation region near the leading edge of the square leading-edge (SL) case, associated with higher vorticity flux compared to the rounded leading-edge (RL) case. Pulsations are observed in the wake region recirculation bubbles through phase-averaging analysis of instantaneous velocity and vorticity. The auto and cross-correlation of reverse flow areas in the SL case exhibit higher temporal correlations in the leading edge and wake region. The analysis of Kelvin-Helmholtz wavelength and frequency spectra indicates a smaller wavelength in the RL case, corresponding to a higher dominant shedding frequency than the SL case. POD reveals the formation of smaller coherent structures with smaller convective velocities, and higher shedding frequency in the wake region of the RL case.