The fluctuating bed shear stress has largely been investigated only for the conditions of uniform channel flows and boundary layers. In practical engineering, the flow conditions are often modified due to the presence of various hydraulic structures. To what extent the modification affects the known characteristics of the bed shear stress is not clear. This study presents experimental results o...

A series of field observations are being carried out to address the objectives outlined above. Measurements of the wave and current field over a broad region of a coral reef are used to determine energy dissipation in an integral sense. Near-bed observations at smaller scales using acoustic profilers deployed on the Rough Boundary Profiler (RBP) then characterize the spatial structure of the bo...

The distribution of the wall shear stress on the bed and sidewalls of an open channel receiving lateral inflow was obtained from experimental measurements of the distribution of the velocity in the viscous sublayer using a laser doppler velocimeter. The experiments were conducted in a 0.4 m wide by 7.5 m long flume. Lateral inflow was provided into the channel from above via sets of nozzles pos...

We want to look at the dynamics of the coherent vortex structures which are generated at the bottom of sea waves by 1) the instability of the laminar boundary layer and the development of turbulence, 2) the nonlinear interaction of the oscillatory boundary layer with a wavy bed of small amplitude and with a sloping bottom and 3) the separation of the boundary layer at the crests of 2-D ripples ...

Abstract: Drag force at the bed acting on water flow is a major control on water circulation and sediment transport. Bed drag has been thoroughly studied in sandy waters, but less so in muddy coastal waters. The variation of bed drag on a muddy shelf is investigated here using field observations of currents, waves, and sediment concentration collected during moderate wind and wave events. To es...

Interfacial boundary conditions determined from empirical or ad hoc models remain the standard approach to model fluid flows over porous media, even in situations where the topology of the porous medium is known. We propose a non-empirical and accurate method to compute the effective boundary conditions at the interface between a porous surface and an overlying flow. Using a multiscale expansio...

Velocities are measured using LDA within the bottom boundary layer for 10 oscillatory flow tunnel experiments involving regular and amplitude modulated flows over a gravel-rough bed sand-rough bed. Corresponding were equivalent in terms of rms velocity, period, skewness asymmetry. The experimental results compared with predictions based on 1DV RANS model k?? turbulence closure. effects modulati...

We performed a series of laboratory experiments to investigate the interactions of a turbulent wave boundary layer with a predominantly silt-size sediment bed. Quasi-steady, turbulent, highdensity suspensions (HDS) formed over a wide range of wave conditions and had near-bed (;1 mm above bed) concentrations ranging from 17 to 81 g/l scaling roughly with the wave orbital velocity. HDS were defin...

The effect of bed roughness on an iso-kinetic chemical plume released into the logarithmic region of the bed boundary layer of an open channel flow is examined. The bed roughness is varied systematically to generate flows in the smooth (painted polyethylene sheets), transitional rough (2.5-mm and 11.5-mm gravel beds), and fully rough (21.0-mm gravel bed) regimes. Concentration fields are measur...