Simulation of the near field of a jet in a cross flow

Abstract

A direct numerical simulation technique is used to predict the time-dependent behavior of a weakly compressible axisymmetric jet exiting normally into a cross flow. Time-averaged velocity fields from the unsteady simulation are in qualitative agreement with previously published experimental and numerical results. The bound vortex system that is observed experimentally is also in evidence in the results of the unsteady simulation, as is the Kelvin -Helmholtz roll-up of the jet shear layer. The horseshoe vortex system often observed experimentally is not seen in the numerical results due to insufficient resolution. The formation of wake vortices in a numerical simulation is observed for the first time. The wake vortex system is found to have a Strouhal frequency of 0.098. The results show that cross-flow boundary layer fluid is lifted up from the boundary layer into these vortices near the rear of the jet exit. This observation is consistent with experimental observations that suggest that the vorticity in the wake system originates in the cross-flow boundary layer upstream of the jet exit.