Drag reduction in simplified geometries of blunt vehicles by means of base blowing*

We perform a study on the turbulent flow around a square-back blunt model, to analyze the effect on both, the near wake and drag coefficient of base blowing with gases of various densities. Different symmetric and asymmetric base and perimetric blowing configurations are tested, showing that the drag coefficient is more efficiently reduced when the rear perimetrical injection takes place at the base bottom. When different blowing-to-freestream density ratios ρ_b/ρ_∞ are investigated, the comparison reveals that injecting a light fluid provides larger drag reductions than blowing fluid of density equal to or greater than that of the free-stream. Complementary simulations have been conducted, which also show the regularization effect of the blowing on the aerodynamic forces and the wake. Finally, high blowing efficiencies have been also found when the injection takes place at the base centre.