Computation of cavitation inception number for isolated surface irregularities is performed with the assumption that cavitation bubbles appear in vortices located within viscous separation zones behind these irregularities. The numerical analysis consists of four parts. The first part is determination of the base pressure within separation zone and irregularity drag by using viscous-inviscid interaction concept for an obstacle in non-uniform incoming flow. This part is validated by the well-known experimental data for cavitation-free flows behind backward-facing steps and within specially designed wind tunnels (by Tani et al {1] and Agarwal & Simpson [2]). The second part is determination of vortex intensity by using the base pressure and drag in an empirical formula. The third part is determination of vortex viscous core from an asymptotic solution of Reynolds equation for the vicinity of a vortex in the turbulent flow. The fourth part is calculation of cavitation inception number for a bubble with taking into account the surface tension effect. The suggested theoretical concept and numerical technique are validated by comparison with measurements for irregularities over flat walls and 2D hydrofoils (by Arndt et al [3] and Holl et al [4]).

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