Instantaneous Pressure Reconstruction From PIV In Compressible Launcher Environments

Abstract

Modern launcher configurations, often characterized by a larger diameter in the payload fairing than the rest of the launch vehicle (hammerhead configuration), face significant challenges during transonic operations, given their susceptibility to flow separation and intense pressure fluctuations. This experimental study aims to reconstruct pressure from PIV under transonic conditions using Taylor's hypothesis. The focus is on the ESA VEGA-E hammerhead launcher model, investigated in the transonic regime at Ma=0.8 and at α=0°. Initially, the methodology of the pressure reconstruction algorithm is described and the validity of Taylor's hypothesis is established through validation with numerical data. Subsequently, the experimental data are first used to provide a general characterization of the flow phenomenon, highlighting key features such as an oscillating shockwave, separated and reattached flows. Later, the reconstruction of pressure from velocity data is compared to unsteady pressure transducer data, for instantaneous, average and standard deviation values, obtaining a very good agreement (ΔCpAvg~0.01-0.02 and ΔCpStd~0.02). The experimental set-up is also designed to showcase the impact of neglecting the out-of-plane velocity component on pressure reconstruction, showing comparable data for CpAvg, while larger discrepancies in terms of CpStd in particular in the separated area region.