Prediction of rocket plume flowfields for infrared signature studies

Abstract

The contribution of various gasdynamic processes affecting rocket exhaust plume structure in the altitude range of 0-60 km is discussed in terms of their relative influence on plume infrared radiation signature predictions. It is demonstrated that spatial details of the nearfield inviscid/shock structure in rocket plumes can appreciably affect flight signature levels at higher altitudes (i.e., /?> 30-40 km). Spatial details are also required in the analysis of most laboratory plumes. Simplified gasdynamic models which globally incorporate the effects of inviscid structure into the startline conditions for a pressure-equilibrated farfield mixing analysis are shown to be adequate in flight signature studies at lower altitudes (i.e., h> 20-30 km). The sensitivities of rocket plume emission to variations in turbulence modeling parameters are presented for flight signature studies at representative lower and higher altitudes in the range of interest. It is demonstrated that, under all conditions, turbulent mixing processes play a dominant role in the prediction of plume signature levels.