Instantaneous pressure reconstruction from PIV in compressible launcher conditions

Abstract

Unsteady pressure fluctuations in transonic launcher configurations represent a major challenge, driven by shock oscillations, flow separation, and compressibility effects. To address these phenomena, this work presents and validates a methodology for reconstructing instantaneous pressure fields from planar (2D2C) and stereo particle image velocimetry (2D3C PIV) data using Taylor’s hypothesis. The approach is first assessed using a simulated PIV dataset of an axisymmetric backward-facing step, representing a launcher base flow configuration. In this case, the Taylor-based pressure reconstruction is validated against reference data and compared with results from a hypothetical time-resolved pressure reconstruction, demonstrating the accuracy of the method. The methodology is then applied to wind tunnel PIV data of a VEGA-like hammerhead launcher model at Mach 0.8 and zero angle of attack. Hammerhead configurations, characterized by payload fairings with a larger diameter than the main body, are particularly prone to separation and intense pressure fluctuations in the transonic ascent phase. The reconstructed pressure fields are analyzed together with unsteady transducer data, providing a general characterization of the flow features (oscillating shock, separation, and reattachment) and showing very good agreement for instantaneous, mean, and fluctuating components (ΔC_{p avg} ~ 0.01–0.02; ΔC_{p std} ~ 0.02). Finally, the analysis highlights the impact of neglecting out-of-plane velocity components, which introduces noticeable discrepancies in separated regions.