Numerical investigation of thermodynamic effect on unsteady cavitation in cascade

Abstract

In the present study, the thermodynamic effect on unsteady cavitation is investigated in cascade in water and liquid nitrogen at different freestream temperatures. Cavitation flowfield is simulated based on self-developed locally homogeneous model of a compressible gasliquid two-phase medium, which is available to treat unsteady cavitation. For calculation of thermodynamic effect on cavitation, simplified thermodynamic model for the locally homogenous medium is used where local saturated vapor pressure changes with depending on rate of heat transfer by evaporation and condensation. In the result of the numerical analysis, the difference of cavitating flowfields is reproduced numerically in water and liquid nitrogen at different freestream temperature concerning the cavity surface profile and distribution of the evaporation region. Also the thermodynamic effect on cavitation in water and liquid nitrogen is investigated by comparing the cavity volumes. Then, well known thermodynamic effect on cryogenic cavitation can be reproduced numerically in liquid nitrogen, where development of the cavity is suppressed according to increase of freestream temperature. On the other hand, the inverse thermodynamic effect, which is experimentally observed in single hydrofoil in water, is reproduced under the condition of unsteady cavitation in water in the present study.