Unsteady compressible Reynolds-averaged Navier-Stokes equations are solved for computing the flowfield over a bulbous heat shield of a satellite launch vehicle at free stream Mach number of 0.95 and 1.20 and at zero angle of incidence. A time-dependent computation is carried out employing a multistage Runge-Kutta time-stepping in conjunction with a finite volume discretization. Closure of these equations is achieved using the Baldwin-Lomax turbulence model. Comparisons are made with the experimental results such as schlieren picture and surface pressure distribution. They are found in good agreement. Numerical analysis is used to determine the characteristics of the fluctuating surface pressure at transonic and supersonic speeds. Standard deviations, higher moments, histograms, and spectrum of pressure and sound pressure level of fluctuating pressure are analyzed in the separated region of the boattail of the heat shield. High frequency components of pressure amplitude and sound pressure levels are found to be dominate at supersonic Mach number as compared to transonic Mach number. [References: 21]
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