Numerical prediction of vortex dynamics in inviscid sheet cavitation

Abstract

Recent studies have indicated that mass transfer models are able to correctly reflect the sheet cavitation dynamics of inertia driven flows, given that the mass transfer model constants governing the source term magnitude are sufficiently large (Koukouvinis and Gavaises 2015) and that enough temporal resolution is provided (Schenke and Van Terwisga 2017). The inertia driven dynamics, characterised by cavity collapse time, shedding frequencies and local pressure impact frequencies, were shown to be insensitive to variations of the mass transfer coefficients in this limit.
This study focuses on an inviscid cavitating flow around a NACA0015 hydrofoil. The flow dynamics are driven by the re-entrant jet as the main mechanism of cavity shedding. A threshold of mass transfer magnitude, temporal and spanwise spatial resolution is identified, beyond which the frequency of local pressure impacts is model parameter independent. Although the excact values of peak pressure loads remain time step size, grid size and model parameter dependent, the sheet cavitation dynamics are considered as well resolved in this regime as far as shedding frequency and characteristic cavity collapse time are concerned. The results are compared to experimental results by Van Rijsbergen et al. (2012).
Based on this, the study further focuses on the mechanism of vorticity generation and vorticity break-up, causing potentially erosive cavitating structures such as horseshoe cavities (Dular and Petkovˇsek 2015).