Hydrodynamics of water-worked and screeded gravel-bed flows

The turbulence parameters over a water-worked gravel-bed (WGB) and a screeded gravel-bed (SGB) are studied, measuring the flow by a particle image velocimetry system in a rectangular flume keeping the flow conditions identical in both the beds. Owing to the water action, the orientation and the alignment of the surface gravels in the WGB were entirely different from those in the SGB. As a result, the WGB possesses higher roughness than the SGB. Analysis of vorticity contours infers that the gravels cause the fluid streaks to have both clockwise and counterclockwise motions in the near-bed flow zone. Besides, the double-averaged streamwise velocity, spatially averaged (SA) Reynolds and dispersive shear stress, SA and dispersive turbulent kinetic energy (TKE) fluxes, and SA TKE budget were analyzed in both the beds. Owing to the higher roughness in the WGB than in the SGB, the turbulence parameters, especially in the near-bed flow zone, remain higher in the former than in the latter.