Oscillatory flow around a periodic array of circular cylinders under bedload dominated sediment transport

We performed high-fidelity, Euler–Euler, two-way coupled simulations at Reδ=40 and a ratio of cylinder diameter to Stokes boundary layer thickness of d/δ=22.4 to assess the evolution of an erodible sediment bed around a non-staggered periodic array of circular cylinders. The oscillatory flow is resolved through the incompressible Navier–Stokes equations, while the sediment bed dynamics are modeled through the Exner equation, considering solely bedload sediment transport through established empirical correlations. To explore a range of scenarios, we examined various oscillatory flow configurations and Shields stress ratios. Our findings reveal that the sediment bed profile is significantly influenced by the initial bed shape and flow conditions, such that the sediment bed profile may not necessarily be symmetric along the flow direction despite flow symmetry. We also observe sediment to remain sequestered near the equatorial edges of the cylinder irrespective of the number of cycles considered or the type of flow and Shields stress ratio. Additionally, when the average Shields stress ratio exceeds unity, we observe the maximum scour depth to reach 10% of the cylinder's diameter within one flow cycle.