Axisymmetric oscillations of an opposing jet from a hemispherical nose

Abstract

The flowfield around a hemispherical nose with a sonic opposing jet in a freestream of Mach 2.5 is computed by a time-accurate algorithm using the axisymmetric Navier-Stokes equations. Five total pressure ratios of a jet to a freestream, 0.816 ∼ 1.633, are examined. The results obtained strongly depend on the total pressure ratio as the previous experimental results did. In some cases, the computed flowfield oscillates intensely in which the drastic change of the jet structure and the surrounding pressure takes place. The flowfield changes from the stable flow to the unstable flow for the same total pressure ratio as in the experiment The mechanism of the oscillations and the condition of transition between both types of flow are interpreted physically on the basis of unsteady numerical solutions here.