UNSTEADY INVESTIGATION OF THE DLR TIC NOZZLE BY DIFFERENT TURBULENCE MODELS

Abstract

Afterbodys of launchers and re-entry vehicles are characterized by large base regions submitted to intense back flow, aerodynamic instabilities and pressure fluctuations on the afterbody and on the nozzle region. Consequently in addition to experimental investigations a necessary capability of numerical tools is the capability to simulate unsteady super- and hypersonic flow fields of such configuration and to resolve turbulent wake flows, interacting with nozzle sections, on realistic launcher configurations. One of the experimental activities in this scope was performed by DLR at the P6.2 facility in Lampoldshausen, Germany, providing an experimental data base for the DLR TIC nozzle under overexpanded cold gas conditions. Key objectives of this test case are the correct prediction of the separation location and the assessment of the resulting unsteady side load torque. The geometry was specified by DLR, including nozzle inner and outer wall and the inflow geometry upstream the nozzle throat. The present computations were performed as a feasibility study, end preliminary results are presented here.Different computations on unstructured grids were carried out with grid adaptation at the shock structures. The test case was investigated by different descriptions of the turbulent flow field such as one equation URANS models and a DES (Detached Eddy Simulation) type simulation as well as laminar conditions. It has to be pointed out that the investigated grids are too coarse for a realistic DES and the resulting turbulence is only insufficiently resolved. Nevertheless the behaviour of the model under these conditions had to be investigated to earn experience for further simulations.