Development of a large‐eddy simulation open channel code

Describes further development of a 3D finite difference code written to model turbulent flows in an open channel with a moving free surface. The code has been developed so that the computational domain can have side‐walls and/or periodic directions and that the flow may also be buoyancy driven. Either a full simulation or large eddy simulation (LES) of the turbulence can be performed. Results are presented of a simulation of periodic streamwise flow in an open channel with parallel side‐walls and also of a thermal jet into an open tank. Both simulations were carried out on a UNIX workstation using resolutions that enable the results to be viewed within an “engineering context”. The LES application demands numerical approximations which conserve mass, momentum and total energy with high precision, and which permit wave motion with very little numerical dispersion or dissipation. The free surface is tracked using a split‐merge technique which combines the volume of fluid (VOF) and height function methods in a way that is conservative.