Identification of inducer cavitation instabilities using high-speed visualization

•A new method which detects cavitation instabilities from images is developed.•Image grayscale values can represent the unsteady pressure measurements.•The grayscale values contain spatial & temporal mode information.•The present method has potential to identify other two-phase flow instabilities. This paper presents a new inducer cavitation instability detection method based directly on quantitative high-speed visualization. The new method uses the grayscale values of pixels, representing fluctuations in the cavity structure, to identify cavitation instability. The method is validated against unsteady pressure measurements in two- and three-bladed inducers. Both unsteady pressure measurements and grayscale fluctuations have been analyzed in the frequency domain via Fourier transformation and traveling wave energy analysis to establish the correspondence between the two types of data. Finally, the new method is applied to demonstrate its capability to detect alternate blade cavitation in a 2-bladed inducer and super-synchronous rotating cavitation in a 3-bladed inducer.