Abstract
Momentum transfer of open channel flows in the lateral direction is important in sediment transport, environment in rivers, etc. Three-dimensional (3D) computations of shallow open channel flows on two parallel lanes of bed with different roughness parameters are presented in this paper. Lateral transfer of streamwise momentum is caused by three different effects, i.e., a cross-sectional secondary current due to turbulence anisotropy (secondary current of the second kind), a turbulence mixing with shear instability and a mass transfer from the rough-bottomed lane to the smooth-bottomed lane due to flow redistribution. Vermaas et al (2011)1) have shown experimentally that the rate of contribution of each mechanism to momentum transfer is closely affected by depth. We tried to simulate the momentum transfer on the roughness transition using three dimensional computational models with a URANS type k- turbulence model. The present numerical results showed that the computational model with a second order non-linear k- model could estimate excellently the each effect on the momentum transfer depending on a flow depth.
