Entropy production analysis in two-phase cavitation flows with thermodynamic cavitation model

摘要

Entropy production is an important parameter for the design and optimization of turbo machines, which is short of intuitiveness in previous studies. The present article investigated the mechanisms of entropy production in cavitation flows around a hydrofoil. The objectives of this research are to (1) reveal the thermodynamic effects with advanced cavitation model, (2) investigate dynamic characteristics of different entropy production terms, (3) analyze the interactions between vorticity and local entropy production rate based on vorticity transport equation. Firstly, water from 298 K to 423 K is investigated around a NACA0015 hydrofoil to reveal thermodynamic effects on different temperatures. Then, in order to study the energy loss due to cavitation, the entropy production theory is firstly applied on two-phase cavitation flows with high temperature water based on homogenous model and its unsteady characteristics is revealed combining with cavity structure. The density corrected turbulence model (DCM) and advanced thermodynamic cavitation model adopted in this research are validate corresponding to experiment. The analysis of local entropy production rate (EPR) indicated that the entropy production rate induced by direct dissipation (EPDD) and turbulent dissipation (EPTD) has the characteristics of spatial and time delay compared with the evolution of cavity instabilities. Moreover, entropy production rate induced by temperature gradients and wall shear stress are slight, while entropy production rate induced by velocity gradients are main part toward total entropy production rate (TEPR).