The enstrophy dissipation in the cavitating flow based on the proper orthogonal decomposition

This study employs the large eddy simulation method to investigate the intricate interplay between the vortex and entropy production in the cavitating flow. Results indicate that the instantaneous total entropy production loss is essentially induced by local enstrophy dissipation of the local vortex structures. The derived Enstrophy term of entropy production rate can be regarded as the simplified entropy production rate (EPR) formula. Analysis of the generation and transportation of enstrophy further reveals the high-value regions of each term of enstrophy mainly concentrated at the vapor–liquid interface, reflecting the influence of the instability of cavities on the formation and dissipation of vortex structures. Based on the simplified EPR formula, the proper orthogonal decomposition (POD) approach is utilized to obtain the coherent structures that dominate the enstrophy dissipation scales in the cavitating flow. The findings reveal that the first four dominant POD modes account for 95.8% of the modal enstrophy dissipation of EPR, and mode 2 captured the large-scale shedding structures at the trailing edge. The frequency of mode 2 and mode 3 approximates the cavity shedding frequency. Additionally, the interaction between the mode enstrophy dissipation of EPR and mode vortex structures is expounded that the magnitude of energy dissipation of EPR carried by mode vortex structures attenuate and the spatial scales of structures decrease with the orders of mode increase. Furthermore, POD reduction technology constructs 95.8% and 99.1% of the original total enstrophy dissipation of EPR, which well resolved the variation of the enstrophy dissipation concentrated at the instability cavity interface and the end of the cavity while eliminating the effect of the small-scale structures with an acceptable accuracy effectively. This study provides a valuable understanding of the coupling mechanism between modal entropy generation and vortex structures of different modal scales in the cavitating flow.