Numerical investigation of compressible cryogenic cavitating flows by a modified mass transport model

Abstract

The objectives of this study are to propose exact numerical methods for the compressible cryogenic cavitating flows and investigate the cavitation behaviors and vortex structures. A numerical modeling framework including large eddy simulations, vapor–liquid equations of state, and a modified mass transport model is presented in this paper. The modified transport model is proposed based on the convective heat transfer in which the convective heat transfer coefficient is associated with the material properties and local temperature. To validate the applicability of the modified model, the liquid nitrogen cavitating flows in the inertial and thermal modes (σ ≈ 0.50, Tthroat = 77.24 K and Tthroat = 85.23 K) are simulated, respectively. Meanwhile, the influence of thermodynamic effects on compressibility is investigated. The numerical method is further utilized to visualize the detailed cavity and vortex structures in different cavitating flow patterns (Tthroat ≈ 77 K, σ = 0.58, 0.39, 0.18). The results show that the predicted cavity structures with the modified mass transport model agree better with the corresponding experimental data. For the thermal mode, since the significant thermal effects restrain the development of cavity, the area of the low sound speed region is smaller than that of the inertial model. The value of the minimum sound speed is larger, so that the Mach number in the cavitation region is reduced. Therefore, the compressibility of the liquid nitrogen cavitation in the thermal mode is weaker. For different cavitating flow patterns, the core region of attached cavities near the throat remains stable during an evolutionary cycle. Compared to the attached cavity region, since some hairpin vortices break into many small-scale discrete vortices, the multi-scale effect of vortex distribution is more remarkable in the shedding cavity region.