Numerical study of thermodynamic effects on liquid nitrogen cavitating flows

The aims of this paper are to study the thermodynamics effects on cryogenic cavitating flows and analyze the specific effects on mass transportation process and flow field structure. Computations of the liquid nitrogen cavitating flows around a 2D quarter caliber hydrofoil are conducted. The Favre-averaged Navier-Stokes equations with the enthalpy-based energy equation, the transport equation-based cavitation model and the k-ω SST turbulence model are applied. The nominal temperature drop ΔT∗, defined as ΔT∗ = (Lρv)/(Clρl), is used to assess the thermodynamic effects on the cavitating flows. The results show that the numerical solution can consistently capture the main features of both pressure and temperature profiles, which show good agreement with the experimental measurements. It is found that the cryogenic cavitation behaviors including pressure and temperature depressions, the variation of thermo-sensible properties, and cavity structures depend on the isothermal free-stream conditions and the thermodynamic effects. The thermodynamic effects significantly affect the liquid nitrogen cavitation behaviors via the following approach that the temperature change during the phase-change process causes the variation of thermo-sensible material properties (especially for the saturated vapor pressure and density), and then the reference free-stream conditions are changed equivalently, resulting in the change of cavity structure. It is indicated that thermodynamic effects could delay or suppress the occurrence and development of the cavitation behaviors. The properties like density ratio R(T∞) and the change of vapor pressure dPv/dT play more significant roles during the nitrogen phase-change process. As temperature increases, the thermodynamic effects become stronger, especially when the temperature is closing to the thermodynamics critical point.