Modal decomposition of the shedding mechanism of partial cavitation in a Venturi Tube

Abstract

The present paper studies the shedding mechanism of partial cavitation in a Venturi Tube, dominated by re-entrant jet and bubbly shock mechanisms, by using two data-driven modal decomposition methods: proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD). According to the snapshot data series obtained by high-speed photography, the modal decomposition and reconstruction of the grey image are carried out. The POD results indicate that the main frequency of the re-entrant jet is higher than that of the shock under the sixth-order mode, and the energy amplitude of the latter is about 20 times that of the former. Furthermore, as the cavitation number increases, the condensation shock mechanism eventually replaces the re-entrant jet mechanism. The DMD results show that the shock behaves obvious traveling wave mode, because the frequency is higher and the phase of the spatial distribution changes evenly under the fourth-order mode. POD and DMD can help to understand the shedding mechanism of partial cavitation. © 2024 Institute of Physics Publishing. All rights reserved.