Turbulence Modeling of Base Drag on Launcher in Subsonic Flight

Experimental wind tunnel tests, conducted to reproduce the base flow past a space launcher during early ascent fight conditions, were numerically simulated by solving the steady Reynolds-averaged Navier–Stokes equations using two different versions of the Spalart–Allmaras model. The launcher model consisted of a cylinder with a circular cross section, an ogival nose, and a centered nozzle that issued a supersonic cold jet embedded in the external subsonic stream. A comparative analysis of the data obtained from the steady-state simulations and from the experimental tests indicated that the launcher base pressure was closely related to the turbulent shear stresses within the jet mixing layer; therefore, accurate modeling of the compressibility effects in the turbulent mixing layer plays an important role in improving the base drag estimates provided by the numerical simulations.