Two- and three-dimensional rotational structures in a cavitating wake

Structures observed in turbulent flows generated by placement of a wedge in a channel with a water flow between 2.5-10 m/sec are reported. The turbulent wake formed by flow over the wedge contained alternating vortices. When a constant Reynolds number was maintained, the Strouhal number was augmented by 20 percent, then diminished when the cavitation was lower than 1.1. The ratio of the distance between the two vortex streets relative to their wavelength was 0.23 when the cavitation was larger than the mean cavitation, and decreased to 0.07 when the cavitation was less than the mean cavitation. In the latter, the vortex cores alternately took the form of a vapor barrier. Outside of the vortex region, two-dimensional roll instabilities were observed in the shear flows. Cavitating filaments were also observed which were connected to the successively alternating vortices.