Thermodynamics Effect on the Mass Transport Process in Cavitation

In order to analyze the influence of thermal effect on the mass transport process in cavitation, the modified Merkle cavitation model and the material properties of the liquid nitrogen at different temperatures are introduced into a software solver via a UDF (user defined function) with the consideration of cavitation influence on source term in energy equation. Computations are then conducted on an axisymmetric ogive in nitrogen under various cavitation conditions. The results are compared with the experimental data to verify the numerical method. Based on the numerical results, the influence of the thermal effect on the mass transport process could be analyzed as follows. The mass transport process includes the processes of evaporation and condensation. In the evaporation process, the cavitation characteristics is not only related to the local cavitation number σ, but also dependent on the liquid-vapour density ratio R(T). With temperature increasing, the gradient of liquid/vapor density ratio dR/dT increases, which would tend to decrease the strength of the evaporation rate; on the other hand, with temperature increasing, the gradient of vapor pressure becomes larger, which would suppress the evaporation rate. In the condensation process, with temperature increasing, (1-φ _l) becomes smaller, that leads to the decrease of condensation rate; while, the increase of max(0, C _p+σ) leads to the strength increase of the condensation rate.