Comparison of mean flow and turbulence around experimental spur dike

An acoustic Doppler velocimeter was used to measure flow and turbulence around an experimental spur dike in a flat and a scoured bed. Differences of mean velocity, turbulent intensity and Reynolds stresses between these two flow fields were compared and analyzed. Upon the formation of scour hole, mean flow velocities in the downstream and lateral directions were reduced, but increased in the vertical direction. The turbulence intensities (u' and v') are much larger, and the vertical component (w') is smaller than that in the flat bed. Bed shear stresses determined from near-bed Reynolds stresses in the scoured bed were smaller than that in the flat bed. These results indicated that local scour has not only significantly reduced bed shear but also contributed to the increase of turbulence intensities in the scouring zone.