Effects of fluid thermophysical properties on cavitating flows

Abstract

We studied the thermo-fluid cavitating flows and evaluated the effects of physical properties on cavitation behaviors. The thermo-fluid (including liquid nitrogen, liquid hydrogen and hot water) cavitating flows around a 2D hydrofoil were numerically investigated. The Favre-averaged Navier-Stokes equations with the enthalpy-based energy equation, transport equation-based cavitation model, and the k-ω SST turbulence model were applied. The thermodynamic parameter Σ, defined as \(\sum { = \left( {\rho _v ^2 L^2 } \right)/\left( {\rho _l ^2 C_v T_\infty \sqrt {\varepsilon _l } } \right)} \) was used to assess the thermodynamic effects on cavitating flows. The results manifest that the thermal energy solution case yields a substantially shorter and mushier cavity attached on the hydrofoil due to the thermodynamic effects, which shows better agreement with the experimental data. The temperature drop inside the cavity decreases the local saturated vapor pressure and hence increases the local cavitation number; it could delay or suppress the occurrence and development of the cavitation behavior. The thermodynamic effects can be evaluated by thermophysical properties under the same free-stream conditions; the thermodynamic parameter Σ is shown to be critical in accurately predicting the thermodynamic effects on cavitating flows. The surrogate-based global sensitivity analysis of liquid nitrogen cavitating flow suggests that ρv, Cl and L could significantly influence temperature drop and cavity structure in the existing numerical framework, while ρv plays the dominant role on temperature drop when properties vary with changing temperature. The liquid viscosity µl slightly affects the flow structure but hardly affects the temperature distribution.