Experimental characterization of the flowfield and cavitation physics of a tip-loaded hydrofoil

Abstract

This paper reports an experimental study of tip vortex flowfield and cavitation inception of a tip-loaded hydrofoil. Vortex strength, wandering, and turbulence statistics are characterized using stereo particle image velocimetry (SPIV) in a water tunnel facility, at a chord Reynolds number of 1.3×106. Cavitation physics are characterized using high-speed videography and dual-hydrophone acoustic cavitation measurements. The loading of the rectangular planform hydrofoil has a maximum at 65% span, 56% greater than that at the root, i.e., the hydrofoil loading is representative of non-elliptically loaded open propellers. Acoustic cavitation inception is quantified and is observed to precede visual cavitation onset using unaided and high-speed imaging. Measurements reported here show that vorticity fluctuations are nearly of the same magnitude as the ensemble vorticity. Instantaneous measurements of vorticity at the trailing edge, 12-chord downstream, and one-chord downstream positions are reported. Their peak magnitudes are located adjacent to the ensemble vortex center and are between four and five times the ensemble mean. The fluctuating vorticity measurements, taken in conjunction with high-speed video observations, provide insight into the hydrodynamic conditions responsible for intermittent cavitation events. The reported measurements elucidate instantaneous and mean turbulence physics associated with vortex cavitation and can provide a validation basis for numerical simulations.