Modeling of the Subgrid-Scale Pressure Distribution in Turbulent Mixing Layer

概要

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Attention was focused on the statistical properties of pressure fluctuation, which is caused by fine-scale vortices in turbulent flow. The aim is improvement in the prediction of cavitation inception due to fine-scale turbulence vortices, which are usually in subgrid-scale (SGS) in Large-eddy simulation (LES). We conducted a finely-resolved direct numerical simulation (DNS) of a spatially-developing turbulent mixing layer in cavitating and non-cavitating (single-phase) conditions. The result under cavitating condition suggested that low-pressure region corresponding to the core of fine-scale vortices could become an origin of cavitation. We applied filtering technique to DNS database under non-cavitating condition to model the low-pressure region of subfilter vortices observed in result under cavitating condition. Filtering volume is corresponding to that in the probable LES. In fully developed turbulence, proportional relation was found out between intensity of SGS pressure fluctuation and turbulent kinetic energy. In addition, Gaussian profile reasonably approximated instantaneous pressure distribution within a filtering volume. We therefore think the possibility of cavitation inception can be accurately estimated by using the intensity of SGS kinetic energy in couple with filtered pressure field.