Fluid Transients in Complex Systems with Air Entrainment

Abstract

This thesis presents a variable wave speed model for the calculation of fluid transients in pipelines with air entrainment. We improve fluid transient modeling by introducing the variable wave speed model: the wave speed is calculated depending on the local pressure and local air void fraction. We also model free gas in the fluid and released/absorbed gas from gaseous cavitation at the fluid vapor pressure. The variable wave speed model can improve the simulation of experimental observations in terms of shape of the pressure peaks, the frequency of the oscillations and the rate of decay over the standard constant wave speed model. A set of experiments were carried out in a single pump pipeline system to test the fluid transient behaviour for the case of pump trip due to power failure and to validate the numerical model. The numerical results from the variable wave speed model were in good agreement with the experimental result. The variable wave speed model was then applied to investigate the fluid transient with air entrainment in the pumping system. We also study experimentally the check valve performances in fluid transients with air entrainment.