Time accurate numerical cavitation erosion prediction of multiphase flow through a venturi

Aktas, Batuhan and Ponkratov, Dmitriy; Sánchez-Caja, Antonio, ed. (2017) Time accurate numerical cavitation erosion prediction of multiphase flow through a venturi. In: Proceedings of the Fifth International Symposium on Marine Propulsors - smp'17 12 - 15 June 2017, Espoo, Finland. VTT Technical Research Center of Finland Ltd, FIN. ISBN 978-951-38-8606-6

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Cavitation erosion affects the efficient operation of the vessel’s propeller, leading to increased costs of operation and maintenance. Traditionally, erosion is predicted using dedicated cavitation tests with utilization of soft paint application or materials as erosive sensors. However, even with materials that are most susceptible to erosion, such tests constitute significant amount of time. It is well-known that cavitation erosion occurs with the impact of high velocity liquid jets generated by the imploding bubbles, also called water hammer effect, and induced shock waves over time. However, it is both not a viable approach to simulate the complete duration of an experiment using numerical methods and extremely expensive in terms of computational time. Therefore, it is a common simplification to assume cavitation events to be repetitive for numerical simulations and based on this assumption there has been a plethora of studies utilizing the numerical simulations for cavitation erosion prediction. Whilst these simulations utilize instantaneous erosive power indicators for cavitation erosion estimation, an approach that takes into account of the summation/accumulation of the erosive intensity over time for precise erosion threshold determination is non-existent. Within this framework this study presents a time accurate numerical cavitation erosion prediction based on the intriguing experimental study conducted by Petkovšek & Dular (2013) that achieved visual cavitation erosion within 1.5 seconds. In addition to the well-known erosive indicators such as Erosive Power Function (Eskilsson & Bensow, 2015), Gray Level Method (Dular et al., 2006) and Intensity Function Method (van Terwisga et al., 2009), in house functions developed by Lloyds Register (LR) Technical Investigation Department (TID) (Ponkratov, 2015; Ponkratov & Caldas, 2015) are used to compare against the experimental results. Comparisons both aided the determination of a time accurate threshold and utilized as an evaluation case for each erosive indicator.