Freestream disturbance measurement by porous Pitot probe in hypersonic wind tunnels

Pitot probes are commonly used for characterizing freestream disturbances in supersonic and hypersonic wind tunnels. However, disturbance resonance between the detached shock and probe surface prevents Pitot pressure from representing true post-shock stagnation pressure fluctuations, making reliable recovery of freestream pressure fluctuations unattainable. To mitigate the resonance phenomenon, a porous Pitot probe is first proposed and tested in a Mach 6 Ludwieg tube upon this work. Results demonstrate significant suppression of acoustic wave interference within the post-shock region when using the porous probe, resulting in substantially reduced measured total pressure fluctuation amplitudes. These findings establish a novel approach for obtaining reliable total pressure fluctuations downstream of the shock wave in supersonic and hypersonic wind tunnels.