TRANSONIC AFTERBODY SIMULATION

Kurzfassung

One challenge of numerical investigations of unsteady super- and hypersonic flow fields is the study of turbulent wake flow and the interaction with nozzle sections at modern launcher configurations. Unsteady side-loads, induced by the interaction of flow separation inside of the nozzle and the launcher wake will strongly influence the design of future main stage propulsion systems. This interaction phenomenon, called buffeting coupling, is one of the main challenges during ascent. The purpose of the presented study is to simulate a combined generic base-flow nozzle configuration under fully turbulent conditions. It is intended as a generic model of the central stage of a launcher, including central body and nozzle area. Experimental data under transonic conditions is available from wind tunnel tests in the scope of the ATAC program. Simulations are carried out with recent turbulence models like detached-eddy simulation (DES). DES is a hybrid technique proposed by Spalart et.al. for the simulation of this kind of turbulent unsteady flows. The idea is to combine the best features of Reynolds-averaged Navier-Stokes (RANS) and the large eddy simulation (LES) for the computation of realistic configurations at high Reynolds numbers. The study was carried out by means of unstructured grids in the whole area including jet- and nozzle flow. Special care was taken on the influence of the time step size on the unsteady results and on grid influences. Comparisons with experimental pressure data, RMS distributions and power spectra have shown good agreement with the predicted DES results.