Numerical investigation of the impact of computational resolution on shedding cavity structures

Artikel i vetenskaplig tidskrift, 2018

In this paper, three-dimensional cavitation is analysed, and in particular how its dynamics is influenced by computational resolution. Cavitation-vorticity interactions are investigated in several spatial resolutions to address impact of the mesh resolution on cavitating vortical flow predictions. Three-dimensional, fully turbulent, cavitating flow around the Delft Twist11 foil is simulated and investigated numerically with particular focus on cavitation structures, shedding dynamics, and vorticity distribution. Implicit Large Eddy Simulation is employed along with the iso-thermal homogeneous two-phase mixture model to conduct the cavitation simulation in OpenFOAM. The paper clarifies the importance of capturing small scales of the flow, and their impact on the cavitation shedding behaviour, especially for flows where the shed cavity is affected significantly by flow vortices. It is shown that the mesh requirement for vortical cavitating flows is governed by the minimum spatial resolution needed to transport vorticity in the flow rather than the resolution needed to simulate the phase change. Better predictions of the mechanisms driving the shed cavity, and its collapse location, will provide a better control over nuisance behaviour in cavitating flows, which is a critical key for design improvements.