Modeling Transitions between Free Surface and Pressurized Flow with Smoothed Particle Hydrodynamics

Abstract

In several engineering applications, it is important to model flows that might transition between free surface and pressurized conditions. An explicit smoothed particle hydrodynamics (SPH) model for incompressible fluid is used to simulate flow in conduits during transitions between free surface and pressurized flow. The model was successfully tested against experimental data and numerical and analytical models in cases available in the literature. To appropriately produce laboratory experiments, procedures to properly define upstream and downstream boundary conditions were developed. These permit the description of conditions given in terms of either flow rate or water depth changing in time. Comparisons with commonly used one-dimensional (1D) models based on the Saint-Venant equations showed the ability of SPH to describe in details fluctuations of water depth, pressure distributions, and velocity fields. In the case of a propagation of a surge wave downstream, the rate at which the conduit pressurized was very close to measurements as well as existing 1D models. However, the dynamics driving the surge wave according to the SPH model appear to be different from these existing models.