Cavitation Erosion Assessment using an Eulerian approach in an incompressible RANS solver

Sören Schenke (Hydrogenious LOHC), Themis Melissaris (Wärtsila) and Tom van Terwisga (MARIN, TU Delft)

Abstract

The CAV24 Conference held in June of this year showed that the quest to predict cavitation erosion is still open to many research attempts. Important choices in the modelling of the cavitation erosion process are made, where the tendency seems to be to choose models that increasingly incorporate details of the erosion process describing the process to a micrometer scale or smaller. We argue in this presentation that this is an inefficient route to predict cavitation erosion, certainly when one considers the relevance of statistical distributions of the critical events that lead to erosion. The proposed method in this presentation is based on energy considerations  of the larger scale cavitation structures and can be regarded as a further development of the original thoughts by (Hammitt, 1963).

The cavitation erosion model that was developed by (Schenke, Melissaris and Van Terwisga, 2019) is based on the energy balance of an imploding cavity. Due to the dominance of inertia in the collapse dynamics of the cavity for relatively large driving pressures, it was concluded that compressibility has a negligible effect on the energy balance of the imploding cavity. It was also found that the aggressiveness of the collapse is only modelled correctly if the instantaneous energy balance is considered, where the potential and collapse induced kinetic energy fluxes are stored until the very last moment of collapse. Only then the stored kinetic energy is converted into a focused collapse impact load. 

This efficient model has been verified and validated with an imploding bubbly cloud, with a model propeller test case as well as with two full scale propellers that suffered from erosion damage. One case consists of a ducted propeller for a steerable thruster (Melissaris et al., 2022), and the other case consists of an open propeller behind a Ro-Ro container vessel  as used in the EU project EROCAV (Melissaris et al. 2023).

Although this erosion model only gives the cavitation impact loads on a surface (most often the propeller) and does not predict the severity of the material damage, it appears to give reliable quantitative predictions with respect to the accumulated surface energy levels and their location on the surface. As such it provides guidance in propeller design or forensic research.

Hammitt, F.G. (University of M. (1963) ‘Observations on Cavitation Damage in a Flowing System’, Journal of Basic Engineering, (85(3)), pp. 347–356. Available at: https://doi.org/10.1115/1.3656601.

Schenke, S., Melissaris, T. and Van Terwisga, T.J.C. (2019) ‘On the relevance of kinematics for cavitation implosion loads’, Physics of Fluids, 31(5). Available at: https://doi.org/10.1063/1.5092711.

Melissaris, T. et al. (2022) ‘Cavitation erosion risk assessment on a full-scale steerable thruster’, Ocean Engineering, 251, p. 111019. Available at: https://doi.org/10.1016/j.oceaneng.2022.111019.

Melissaris, T. et al. (2023) ‘Cavitation erosion risk assessment for a marine propeller behind a Ro-Ro container vessel’, Physics of Fluids, 35, 013342. Available at: https://doi.org/10.1063/5.0131914.