Numerical simulation of the starting flow down a step

This is the authors' abstract. We don't add key points for this paper.

The starting flow down a step in an open channel is simulated using a vortex method. A mixed Eulerian-Lagrangian scheme based on the vortex-in-cell algorithm and random walk diffusion is used with a non-uniform mesh. The comparison of numerical and experimental instantaneaous streamline plots show good agreement, especially for early stages of the flow development. It is also shown that, during intermediate stages of the flow development and for the range of Reynolds numbers investigated, the distance from the step to the reattachment point of the main vorticity domain increases linearly with the dimensionless time. Again, good agreement is obtained between experimental data and computed solutions.