Combined experimental and computational investigation of the influence of micro vortex generator on incipient cavitation mode

The objective of this paper is to investigate the effect of a passive control method on the incipient cavitation mode around a hydrofoil. Two micro vortex generators (mVGs) with different positions are installed on the leading edge (LE) of the NACA (National Advisory Committee for Aeronautics) 66 hydrofoil. The mVG-1 has the same structural parameters as the mVG-2, but it is closer to the LE of hydrofoil. A high-speed camera is used to record the transient behavior of the cavitating flow. The large eddy simulation combined with a mass transport model is applied to analyze the influence mechanism of mVG on the incipient cavitation mode. The results show that the three typical incipient cavitation modes are observed on the baseline hydrofoil, i.e., spot cavity, patch cavity, and finger cavity. The mVG induces the generation of vortex shaped like thin strips of fingers at its trailing edge, called the fingerlike vortex cavitation. The neighboring fingerlike vortices constitute a pair of counter-rotating vortices with equal sizes and opposite directions. It influences the near-wall flow state upstream and downstream of mVG and, thus, the incipient cavitation structure. For the mVG-1 hydrofoil, the fingerlike vortex cavitation is a unique form of the incipient cavitation mode, making the cavitation onset position fixed at the mVG tail. For the mVG-2 hydrofoil, the mVG has a significant effect on the incipient cavitation structure at small attack angles, changing both the incipient cavitation mode and position.