Spatially averaged near-bed flow field over rough armor layers

摘要

Results of a laboratory study carried out to investigate the interaction between water worked gravel-bed roughness and the near-bed flow field are presented. Vertical velocity profiles were measured with a 3D-Laser Doppler Anemometer at 24 randomly distributed locations within a defined test section. Bed topography was scanned with a laser displacement meter. The spatial heterogeneity of flow velocities and turbulence parameters in the near-bed region is shown by means of form-induced stresses which follow from the doubleaveraged Navier-Stokes equations. Form induced stresses are also used to investigate the subdivision of the near-bed flow field into roughness and logarithmic layer dependent on roughness geometry. The influence of the definition of geometrical roughness parameters on hydraulic parameters such as water depth and bed shear stress is discussed.