Comparative study of surface pressure fluctuations over bulbous heat shields at mach number=0.95

摘要

Time-dependent turbulent compressible Reynolds-averaged Navier-Stokes equations are solved for computing flowfield over the bulbous payload shroud of a satellite launch vehicle at a freestream Mach number of 0.95 and at a zero angle of attack. Numerical simulation has been carried out employing a multistage Runge-Kutta time-stepping scheme in conjunction with a finite volume discretization. The closure of these equations is achieved using the Baldwin-Lomax turbulence model. Comparisons have been made between numerical and experimental results such as schlieren pictures, position of terminal shock on forebody cylinder and surface pressure distributions. A good agreement is found between them. A separated flow zone on the boat tail region is observed and is found to be having unsteady pressure fluctuations. Standard deviation, higher-order moments and spectrum of surface pressure levels of the fluctuating surface pressure are analysed in the separated flow region of the boattail of the heat shield. A comparative study of surface pressure fluctuations and spectrum of sound pressure levels has been made for two different types of heat shield configurations that are close to the recommended NASA specifications.