Unsteady Navier-Stokes Rocket Nozzle Flows

Abstract

The space-time conservation element/solution element (CE/SE) method in conjunction with an unstructured mesh generator is applied to solve unsteady Navier-Stokes (N-S) rocket nozzle flows. The space-time CE/SE method considers space and time as a single entity, preserves both local and global flux conservation in the solution procedure, and provides accurate, unsteady analysis results for both the N-S (viscous) and the Euler (inviscid) nozzle flows. No computational difficulty is encountered with the unstructured mesh using high-aspect-ratio triangular elements in the viscous boundary layer. The method automatically captures distinctive features of flow separations and complicated wave interaction patterns of shear layers, incident shocks, reflected shocks, slipstreams, Mach disks, and traveling vortex rings during unsteady flow development in the nozzle and in the near field of its exhaust jet without using any turbulence model or flow separation model. Detailed calculations are carried out for overexpanded flows inside the JPL axisymmetric, convergent-divergent nozzle. Salient characteristics of the unsteady N-S flows compared with those of the steady-state flows are revealed. Excellent agreement is obtained between analysis results and experimental test data at various ambient pressure conditions.