ГІДРОДИНАМІЧНА МОДЕЛЬПРОФІЛЮ ШВИДКОСТІ РІДИНИ НА МЕЖІ З КАВЕРНОЮ

The purpose of the paper is to find the velocity profile of the liquid at the interface with the cavity for the case of flow without and with evaporation, as well as to analytically analyze the effect of vapor extraction from the cavity on its geometric dimensions. Methodology. The work is based on an integrated approach that combines methods of hydrodynamics of multiphase media, boundary layer theory, and heat and mass transfer laws. Mathematical modelling of the velocity distribution in the diffusion boundary layer of the cavity is implemented using self-similar variables and the integral of probabilities. Results. A system of equations is proposed for finding the velocity profile at the interface with the cavity, taking into account the processes of vapor evaporation into the cavity. It is established that the high intensity of heat transfer in cavitation devices is due to the specifics of evaporation from the surface of the cavity, where, as a result of an increase in local flow velocities, the pressure decreases significantly below the pressure of the surrounding liquid. It is proven that this pressure drop activates a complex of additional effects that significantly increase the rate of vaporization. Scientific novelty. For the first time, the mutual influence of local hydrodynamic parameters of the cavitation flow and the kinetics of interphase heat and mass transfer at the interface of the media “liquid – vapor cavity” has been comprehensively taken into account. A refined mathematical description of the velocity distribution in the boundary layer has been obtained, taking into account intensive evaporation based on the integral error function, which allows predicting the dynamics of changes in the size of the cavity at different temperature regimes of the subcooled liquid. Practical significance. The results obtained are the basis for engineering calculations and future optimization of the design parameters of cavitation devices for water desalination and allow for a preliminary calculation of the process before experimental verification and implementation of a full-scale experiment.