«It ÜMA AIAA 98-3623 Numerical Investigation of Exhaust Plume Radiative Transfer Phenomena

Accurate simulation of radiative heat-transfer effects from the rocket engine exhaust plays an important role for the proper characterization of missile base heat loads. To promote improved radiative transfer solutions, careful attention to the physical flow-field models is paramount. Use of a generalized fluid dynamic model can assist in the close approximation of the actual base heating by solving the fully coupled, two-phase, chemically reactive, Navier-Stokes equations in multiple dimensions. Solutions to this set of governing equations enables flow simulations for the complex expansion of the fuel-rich engine exhaust gases. Some key features for these expansion processes include phenomena such as baseflow recirculation and separation, atmospheric entrainment, and shock structures that result from interactions with the vehicle and the natural expansion of the plume flow field into the quiescent environment. Threedimensional aspects of the reacting gas dynamic flow processes are also very important components, especially in the missile base and the near engine exhaust regions. A computer model called GPACT (General Propulsion Analysis Chemical Kinetic and Two-Phase) includes numerical approximations for these physical processes, and is currently under development. GPACT was previously applied to simulate the Titan II flow field at 46 km, in its entirety, and to model the flow field of a subscale liquid-propellant rocket engine (LRE) missile fired at 10.1 km in a ground test environment. The ability of this flowfield model to simulate physical details of the flow processes contributing to the radiative heating will be presented in this paper. A variety of flow-field model approximations are examined in order to isolate the influences of three dimensionality and upstream solid boundary effects on the calculations. Radiative heat-transfer solutions are obtained for several flow-field examples in order to exemplify the importance of flow-field approximations on the radiation component of the overall base heat loads.