The Lagrangian coherent structure-based investigation of cavitating flows around a disc

The cavitating flows around a disc is analyzed based on finite-time Lyapunov exponents (FTLE) and Lagrangian coherent structure (LCS). The inhomogeneous model is utilized to predict the interaction between vapour and water flows in the simulation. The simulation results are confirmed by the experimental data. The analytical result shows that LCS defined by the ridges of FTLE can be divided into straight and circular LCSs. The straight LCS reflects that the disc hinders the motion of fluid, and the circular LCS distinguishes the large-scale vortex and identifies the center of vortex accurately. The vortex is intensified and the distribution is concentrated with the development of cavity. It is the periodic change in the intensity of re-entrant flow that causes the periodic expansion and contraction of cavity. A low FTLE region emerges near the support-rod with the increase in re-entrant flow, and there exists a corresponding relationship between the region and the start point of streamline.