Three-dimensional transient simulation of water filling and draining of gravity flow based on Lattice Boltzmann Method

The traditional one-dimensional method of characteristics is available to analyze the transient flow of system level in full pipe flow. As for water filling of empty pipeline and water draining of water-filled pipeline, it is difficult to analyze with this method as the boundary conditions are changing along with the location and time. Meshless Lattice Boltzmann Method was used in this investigation to simulate these two circumstances in the gravity flow water-delivery system respectively. We visually obtained, by this method, the changing process of liquid level, total time of the filling and draining process, flow state around the butterfly valves in the pipe inlet and outlet respectively. Meanwhile, time history data of water flow rate and submersed fraction on the cross section behind the valves were extracted as well. CFD method used in analysis of three-dimensional pipeline flow in system level is an innovation of this research that it not only makes the result more accurate, but also details and visualizes the local transient flow state in pipeline system of gravity flow.