LES of tip-leakage cavitating flow with special emphasis on different tip clearance sizes by a new Euler-Lagrangian cavitation model

Abstract

In the present paper, a new cavitation model proposed by Cheng et al. (2020a) combined with LES is utilized to simulate the tip-leakage cavitating flow around a NACA0009 hydrofoil, which considers the effect of non-condensable gas on cavitation. The predicted tip-leakage vortex (TLV) cavitation agrees well with available experimental observations. Based on the numerical results, the influence of different tip clearance sizes on tip-leakage cavitating flow is discussed in detail. It is shown that with the increase of tip clearance size, the intensity of tip-separation vortex (TSV) cavitation decreases, while the intensity of TLV cavitation increases first and then decreases. Their fusion position moves downstream with the increase of tip clearance size. Moreover, the numerical result implies that the size of tip clearance also has an impact on characteristics of sheet cavitation, such as its length and shape. Finally, the vorticity transport equation is utilized to investigate mechanisms of vortex development around TLV cavitation. As tip clearance size increases, the effect of stretching term decreases, while that of dilatation and baroclinic torque terms increases first and then decreases. However, it is found that the stretching term is dominant in all investigated cases regardless of tip clearance size.