Unsteady cavitation dynamics over a pitching NACA0015 hydrofoil

Cavitation due to flow unsteadiness is a significant source of unwanted noise and erosion in hydrodynamic applications. Quantifying underlying cavity structure and unsteadiness can help determine the erosive potential and `aggressiveness' of the cavity to make suitable hydrodynamic design changes. This study focuses on the cavitation dynamics over a NACA0015 hydrofoil (165mm chord) subject to pitching motion at different cavitation numbers (1.3 to 3.5), using time-resolved X-ray densitometry and high-speed cinematography. In addition, synchronized unsteady surface pressure and cavity static pressure measurements are also performed The dynamics of the cavity collapse as the foil pitches between pre-set angles of attack (10 to 0deg and 7 to 0deg) is studied at different angular accelerations. The effect of this pitching motion on cavity evolution and collapse mechanisms (re-entrant jet induced and bubbly shockwave driven) is reported.