Turbulent separations around a slanted-back Ahmed body with square and rounded leading edge

Abstract

An experimental study was conducted to study the effects of rounded (RL) and squared leading edge (SL) on the time-averaged and temporal characteristics around a slanted-back Ahmed body. Measurements were conducted at two Reynolds numbers of ReH = 1.70 × 104 and 3.60 × 104. The results showed that sharpening the leading edge induces a larger recirculation region near the leading edge of the body, but slightly reduces the recirculation region in the wake region. In both leading and near wake of bodies, the recirculation length for SL cases was independent of ReH, but for the RL body, it decreases in the leading edge and increases in the wake region as ReH increases. The analysis of turbulent structures showed that the extent of the region of elevated integral timescale around the body is larger in the SL case than RL one. Statistical analysis showed that sharpening the leading edge suppresses downwash flow, which in turn reduces the shear layer interaction behind the body and decreases the dominant shedding frequency. The dominant frequencies obtained using velocity fluctuations, reverse flow area, and the coefficient of the first proper orthogonal decomposition confirmed that the dominant frequency near the leading edge and the wake region of the RL body increases with ReH, while it is insensitive to ReH for SL case. The analysis performed in the spanwise plane also revealed that a region with higher streamwise mean velocity forms in the wake region of the RL body, which originates from the higher flow deviation near the trailing edge of the body.