Computation of cavitation inception numbers for 3D surface irregularities

Existence of three scales challenges computations. The suggested multi-step iterative numerical method is a modification of the method already used by the author for cavitation inception behind 2D irregularities. The initial unsteady problem is broken down into two steady problems. The first of them is determination of the average separated flow behind the irregularity. This problem is solved using viscous-inviscid interaction approach, with 3D pressure computation. The second of them is determination of cavity equilibrium within the vortex core. This problem is solved with the assumption on a small influence of the vortex on the surrounding flow, but the vortex characteristics are linked to the computed turbulence characteristics in the separation zone. Intermediate validations with various experimental data are shown for all steps of the computational methods. Comparisons of computed and earlier measured cavitation inception numbers for hemispheres and cylinders submerged in the flat wall boundary layer are provided.