Oscillating flow over a porous bed*

Sediment transport is important in a wide variety of settings, and the interaction between turbulence and mobile beds is a common feature across many fields of research.  While much work has been done to understand and predict the onset of sediment motion in shear-driven turbulent boundary layers, there is limited information for cases in which the turbulence is dominant and mean shear is minimal.  We performed an experiment to observe the failure of a subaqueous granular bed due to pressure fluctuations in an oscillatory flow above the bed.  The amplitude and frequency of the oscillations are varied in order to determine how the intensity of the fluctuations influences the deformation of the bed. We find that there are intervals in frequency and amplitude that result in the development of a heap in the bed.