Investigation of cavitation shedding mechanisms including reentrant jet and shock wave by Eulerian-Lagrangian multiscale simulation

Sheet-to-cloud cavitation in a Venturi pipe is investigated experimentally and numerically in this work. The multiscale vapor structures are simulated by Eulerian-Lagrangian multiscale modeling. The volume of fluid method with adaptive mesh refinement is employed to capture the macroscale cavity features, utilizing the large eddy simulation approach. The results of mesh sensitivity study demonstrate that second-order refinement is capable of capturing phase details and cavitation shedding behaviors. A comparison with experimental results reveals the mechanisms of different types of cavitation shedding induced by reentrant jet and shock wave. Taking microscale bubbles into account using the Lagrangian approach and achieving Eulerian-Lagrangian coupling, the multiscale cavitation features, including the morphological evolution of large cavities and characteristics of microbubbles, are accurately reproduced. The evolution features of microbubbles during pressure wave or condensation shock propagation are well recognized by different changing rates. The results indicate that shedding mechanisms in Venturi pipe cavitation can be categorized into three types: reentrant jet, condensation shock, and pressure wave. In the three conditions investigated in this work, shedding cycles are found to be mainly induced by the reentrant jet (sigma = 1.03), reentrant jet, condensation shock, and pressure wave (sigma = 0.64), and condensation shock (sigma = 0.39), respectively, with a decrease in the cavitation number.