Cavitation analysis of a Delft twisted hydrofoil using multi-process cavitation model

Cavitation is essentially formed of a combination of multiple processes. Most of the conventional cavitation models consider these in a single model, and the conservation equation for void fraction of cavitation bubbles is solved. To understand the relationship between cavitation and turbomachinery performance, not only void fraction, but also states of cavitation bubbles such as number and radius may become useful data. The multi-process cavitation model proposed by Tsuda and Watanabe is one of the solutions. This model has been implemented into commercial CFD software scFLOW. To validate the implemented cavitation model, cavitation around a Delft twisted hydrofoil was analyzed, and the result was compared with past studies. From a parametric study of the bubble growth coefficient in this cavitation model, it was found that 0.2 for expansion and 0.05 - 0.1 for shrinkage are appropriate. Cavitation shedding frequency and cavity volume agreed well with the past studies by using those coefficients. Since the multi-process cavitation model provides detailed cavitation bubble states, a new index is proposed to detect bubbly regions and its distribution compares well with experimental data. This implies that the multi-process cavitation model will help us to predict cavitation noise and erosion risk as well as to understand the mechanism of the cavitation phenomenon.