Simulation of viscous water column collapse using adapting hierarchical grids

An adaptive hierarchical grid based method for predicting complex free surface flows is used to simulate collapse of a water column. Adapting quadtree grids are combined with a high-resolution interface capturing approach and pressure based coupling of the Navier Stokes equations. The Navier-Stokes flow solution scheme is verified for simulation of flow in a lid driven cavity at Re=1000. Two approaches to the coupling of the Navier-Stokes equations are investigated as are alternative face velocity and hanging node interpolations. Collapse of a water column as well as collapse of a water column and its subsequent interaction with an obstacle are simulated. The calculations are made on uniform and adapting quadtree grids, and the accuracy of the quadtree calculations is shown to be the same as those made on the equivalent uniform grids. Results are in excellent agreement with experimental and other numerical data. A sharp interface is maintained at the free surface. The new adapting quadtree-based method achieves a considerable saving in the size of the computational grid and CPU time in comparison with calculations made on equivalent uniform grids.