Modelling approaches to acoustic cavitation in transmission pipelines

A general treatment of acoustic cavitation was presented, including both fluid dynamics instabilities that can occur at cavitation inception as well as non-equilibrium thermal and mechanical effects during bubble dynamics. Different approaches to cavitation modelling were considered and compared.A novel barotropic cavitation model has been developed, based on the partial differential equations governing the mass-conservation and momentum balance. The fluid has been taken as a homogenous mixture of a pure liquid, its vapor and a quantity of gas, both dissolved and undissolved. The analytical expression for the vapor source term driving cavitation has been carried out by means of the energy conservation equation and a general formula for the sound speed in homogeneous bubbly flows has been derived.A recently developed conservative, implicit, high-resolution, second-order accurate numerical scheme was applied to solve the equations governing the pipe flow. The resultant computational algorithm was assessed through comparison with experimental data referring to a system made up of a pipe connecting two constant-pressure reservoirs of water. The model predictions were examined and discussed in order to underline the most interesting fluid-dynamic phenomena, such as the dynamics of shock waves arising at cavitation collapse.The influence of the frequency-dependent friction on the simulation of the pressure wave dynamics in the presence of cavitation was also analyzed and discussed.