Author(s): Hideto Yoshimura
Linked Author(s):
Keywords: LES; Strip roughness; Open-channel turbulence; PIV; Immersed boundary method; Separation vortex
Abstract: Open channel flow with strip roughness is investigated by a large eddy simulation (LES) using an immersed boundary method to represent the arbitrary bottom roughness shape. In the simulation a sophisticated SGS model, the MTS-SGS model proposed by Inagaki et al. (2002), is used to simulate the flow near the boundary without a damping function. In addition to the simulation, flow visualization experiments using the particle image velocimetry (PIV) are performed to compare the results with simulation. The hydraulic conditions for the simulation and 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 in the present research. After confirming that distribution of statistical properties such as turbulent intensities calculated by LES agrees fairly well with those by PIV, we paid attention to the generation of vortices influencing the water surface velocity field. It was made clear that the proposed LES model is capable to simulate the time-dependent features of the vortices separated at the strip roughness and the three-dimensional structure of the separation vortex just reaching the water surface.
Year: 2007