Wake transitions and steady -instability of an Ahmed body in varying flow conditions

The paper investigates experimentally the flow past a flat-back, taller than wide Ahmed body having rectangular base aspect ratio $H/W=1.11$ in context of ground vehicle aerodynamics. Parametric studies at Reynolds number $2.1\times 10^5$ explore sensitivity aerodynamic force and pressure distribution with respect to varying conditions defined from variable clearance $C$ (taken mid-distance front rear axles body), pitch angle $\alpha$ , yaw $\beta$ (equivalent crosswind). Two-dimensional parametric maps spaces $(\beta,C)$ $(\beta,\alpha )$ are obtained for parameter ranges covering real road driving conditions. study gradient reveals non-trivial sharp transitions identified as significant changes near wake orientation both spaces. All unsteady correspond fluctuation crises vertical component only. These summarized phase diagram representations. Both diagrams can be unified large $(\beta,C_r)$ space, where $C_r$ separating lower edge is simple function . impacts clearly drag, lift side coefficients. contribution steady $z$ -instability (Grandemange et al. Phys. Fluids vol. 25, 2013 pp. 95–103) assessed by repeating analysis cavity. As reported previously, cavity suppresses instability symmetrizing wake. A domain existence finally proposed attitudes map regions mean lateral coefficients significantly decreased presence In addition, it found that forces less all do not transitions.