Large eddy simulation of self-excited oscillation inside Helmholtz oscillator

In the present study, a large eddy simulation was conducted to simulate the three-dimensional cavitation turbulence flow inside a Helmholtz oscillator under a high Reynolds number. Numerical results show reasonable agreement with available experimental observations and data. Under the validated solution strategy, the cavitation flow is visualized in a straightforward manner and indicates the primary shedding and secondary shedding induced by the shear layer and collision wall. The evolution and the interactions between cavitation and vortices are well captured and discussed in detail. The results show that flow inside the chamber can be divided into three stages, the boundaries of which are where the vortex reaches the wall surface and where a stable vortex ring is formed on the collision wall. The cavity length has an important influence on frequency, indicating that axial constraints have a greater effect on frequency than radial constraints do. A coherent structure is used to reveal the influence of vortex-wall interactions, and the structure shows that there is a close relationship between the vortex-cavitation interaction and the flow mechanism. Our work provides insight into the internal flow of the Helmholtz oscillator and represents further efforts to demonstrate the mechanism of the oscillation jet. (C) 2020 Elsevier Ltd. All rights reserved.