Abstract
A large eddy simulation (LES) of turbulent open-channel flow with strip roughness is performed together with the image analysis by the particle image velocimetry (PIV). In the simulation, an immersed boundary method is introduced in order to be able to simulate arbitrary channel bed topography. In addition, we used a sophisticated LES model to simulate the flow near the complicated boundary without using a damping function. The hydraulic conditions for the simulation and the experiment are restricted to a relatively small Froude number (Fr) flow, e. g. Fr less than 0.25, in order not to generate appreciable water surface fluctuation. The results show favorable agreements regarding the statistical properties such as the mean and the Reynolds stress distributions. Additionally, the instantaneous flow structure at the instance when a separation vortex hit the water surface is investigated, showing that the separated vortex ascends up to the water surface and locally decelerate the convection velocity of the surface profile.
