Abstract
In this paper, the ITTC Standard Cavitator is numerically investigated in a cavitation tunnel. Simulations at different cavitation numbers are compared against experiments conducted in the cavitation tunnel of SVA Potsdam. The focus is placed on the numerical prediction of sheet-cavitation dynamics and the analysis of transient phenomena. A compressible two-phase flow model is used for the flow solution, and two turbulence closures are employed: a two-equation unsteady RANS model, and a hybrid RANS/LES model. A homogeneous mixture model is used for the two phases. Detailed analysis of the cavitation shedding mechanism confirms that the dynamics of the sheet cavitation are dictated by the re-entrant jet. The break-off cycle is relatively periodic in both investigated cases with approximately constant shedding frequency. The CFD predicted sheet-cavitation shedding frequencies can be observed also in the acoustic measurements. The Strouhal numbers lie within the usual ranges reported in the literature for sheet-cavitation shedding. We furthermore demonstrate that the vortical flow structures can in certain cases develop striking cavitating toroidal vortices, as well as pressure wave fronts associated with a cavity cloud collapse event. To our knowledge, our numerical analyses are the first reported for the ITTC standard cavitator.
Highlights
Cavitation, when it occurs, is a cause of many detrimental effects on marine propellers and turbomachinery
Our flow model is based on a compressible form of the Reynolds-averaged Navier–Stokes (RANS) equations where an assumption is made on the homogeneity of the fluid mixture among the different phases involved in the computation [23,24]
We studied the ITTC Standard Cavitator numerically in a cavitation tunnel at different cavitation numbers
Summary
Cavitation, when it occurs, is a cause of many detrimental effects on marine propellers and turbomachinery. If the sheet cavity is thick, the break-off cycle is relatively periodic with approximately constant shedding frequency In these cases, a Strouhal number St = f lre f /Ure f can be determined. The shedding behavior is mainly governed by the development of the re-entrant jet, vortical structures and turbulent flow near the foil, i.e., the unsteady dynamics of especially the liquid phase. High-fidelity turbulence modelling is typically needed to capture a detailed flow field for the prediction of the dynamics of cavitation and its consequences such as erosion and noise [9,10,11,12].
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