Analyze and Control of Near-Wake Flow on a Simplified Car Geometry

A 3D numerical simulation, based on the Lattice Boltzmann Method is carried out on a rectangular body (initially proposed by Ahmed [1]) to analyze the influence of blowing devices on the near-wake flow of a generic blunt body model. First, the results obtained without control are compared with experimental data from the literature. An open loop flow control strategy is then applied by setting blowing slots around the periphery of the body base. The blowing velocity is set to 1.5 V₀, V₀ being the upstream velocity. The resulting aerodynamic drag reduction is then analyzed by studying velocity, vorticity and total pressure loss distributions in the near-wake flow. Typical results show that a 29% drag reduction is obtained at a blowing angle of θ = 45° with respect to the base surface. Blowing jets are analogous to separated longitudinal fluidic elements which permit to reduce the transversal wake section by inclining the streamlines in the near-wake flow. The momentum introduced into the flow leads to a reduction in the wake total pressure loss and an increase in the base static pressure distribution. Finally, a parametric analysis is conducted on the blowing velocities in order to optimize the efficiency of the chosen control strategy, i.e. to minimize the ratio between the energy used to generate the jets and the energy saved through aerodynamic drag reduction.