Open-channel flow over evolving subaqueous ripples

We have numerically investigated the turbulent flow and sediment grain motion in an open-channel configuration over a subaqueous bed featuring two-dimensional transverse ripples at moderate Reynolds number super-critical Shields values. The simulation data, which were generated by means of particle-resolved direct numerical simulation, are same as our previous work (Kidanemariam & Uhlmann, J. Fluid Mech. , vol. 818, 2017, pp. 716–743). By carefully choosing computational box sizes, we able to accommodate single ripple units form initially flat wavelength equal domain length. then evolve into their asymmetric shape relatively quickly eventually migrate downstream steadily while maintaining size. In present study, using ripple-conditioned phase-averaging procedure, obtain novel insights evolution particle bedforms, particular spatial structure basal shear stress its relation rate. Our analysis confirms that boundary shear-stress maximum is located upstream crest, rate essentially phase with topology, average difference between two range 18–19 diameters for considered parameter further confirm link flux relaxation behaviour observed shear-stress/geometry lag, evaluation saturation length scale.