The influence of cavitation and the degree of overlap of the flow of cylindrical flow bodies on the flow pattern, hydrodynamic and spectral characteristics of a flat-type hydrodynamic generator

The paper presents the results of studies of flow behind cylindrical flow bodies in a flat-flow hydrodynamic generator, obtained on the hydrodynamic bench of the experimental base of the National Scientific Center NBMT RAS with the degree of flow blocking by flow bodies St/S0 = 10-80%, Re numbers (0,5-5) · 105, PVH inlet pressure = 0,1-0,8 MPa. It was found that with the same pressure drop two different types of flow can be realized behind the flow bodies: with a developed cavitation zone, within which there is an extensive low pressure area and without it, but with the formation of vortex structures with the presence of centers of cavitation bubbles in them. At a certain value of input to output pressure, which is constant for each value of the degree of overlap of the flow, powerful pressure peaks of the resonant type arise with an amplitude of 2-2,5 times the maximum value of the input pressure. The frequency of occurrence of these pressure peaks increases linearly with increasing pressure drop, and decreases by an order of magnitude with an increase in the degree of overlap of flow up to 80%. The frequency dependence of the number Re for each value of St/S0 is linear. The value of the Strouhal number St with an increase in St/S0 increases linearly with St/S0 = 0,82 and the value St = 1,2.