The present paper deals with the simulation of the fluid dynamic behavior of transverse gas injection in turbulent supersonic air streams. The Favre-averaged Navier-Stokes equations are solved for a multicomponent mixture of gases. A two-equation k-e turbulence model is employed that properly accounts for low Reynolds effects. The governing equations are solved by a finite volume approach with the k-e model equations fully coupled with those of the mean flow, and an implicit treatment of the source terms. Several test cases are considered and the results are compared with available experimental measurements.