HEAT FLUX ESTIMATION ON RE-ENTRY VEHICLE BASE CAVITY AT HYPERSONIC CONDITIONS USING CFD
Flight vehicles used in space/defense applications typically
have re-entry configurations in the form of blunt cones which
are subjected to severe aerodynamic heating during re-entry
phase of the trajectory. At the beginning of re-entry, wall
temperature will be lower and subsequently gets heated to very
high temperature due to high heat fluxes which may result in
mission failure. Cavities formed during stage separation are
subjected to high heat flux/ high temperature whose
measurements through experiments is a challenging task. The
prohibitive costs involved in performing even scaled down
laboratory experiments and absence of analytical solutions
adds to the complexity thereby making CFD a viable
alternative. However, near exponential growth in the numbercrunching abilities of computers enables quick solutions of moderate accuracy. Thus use of CFD in estimating the heat flux at re-entry conditions is the state-of-art solution which reduces lead time, cost and also gives better insight into various parameters for analysis. In this paper, heat flux is estimated using CFD on a generic re-entry configuration having base cavity which is formed due to the separation of inter-stage motor from full flight vehicle configuration.
Re-entry flight conditions are identified for estimating the
heat flux from ρV3 plots of different trajectories. They are (1) M=5, Altitude 3 Km, (2) M=8, Altitude 7 Km, (3) M=13, Altitude 13 Km and (4) M=16, Altitude 20 Km. For each condition four different wall temperatures (Tw) 500 K, 1000 K, 1500K and 2000 K are considered. CFD simulations have been carried out using ANSYS FLUENT code in N-S mode with k-ω SST turbulent model. 2-D Axi-symmetric half body structured grid of size 0.12 million using GAMBIT is generated capturing base cavity geometry. Variation of heat flux along the cavity wall at all four conditions is studied. This data is very much useful for the design of thermal protection system of payload.