Local scour around a monopile using semiconical protection in a steady current

Experimental investigation of current-induced local scour around composite bucket foundation in silty sand

Herein, a two-dimensional numerical model was established to examine the effect of Reynolds number on local scour around a pipeline under steady current by solving the Naiver-Stokes equation with shear stress turbulence (SST) k-ω closure. Suspended load and bedload transport rates were considered in the model. The numerical results revealed that the Reynolds number can considerably affect the local scour around the pipeline. However, earlier works often ignored the effect of Reynolds number on local scour. An empirical equation for the variations in the maximum scour depth with Reynolds number was presented based on present study.

The effect of Reynolds number (Re) on the local scour around a monopile encountering steady current was investigated experimentally in a water flume. The experiment was performed using circular cylinders with different diameters under two different freestream velocities, covering both clear-water and live-bed scours and a Reynolds number range of approximately 9,000–60,000. The time-series of the scour depth was recorded during the whole scour process and the scour pit was scanned after the scour process reached equilibrium. Results are presented in terms of the equilibrium scour depth, the time-scale of the scour process and the three-dimensional scour profile at different Reynolds numbers. For both clear-water and live-bed scours, the time history of the scour process indicate that the time-scale becomes larger as Re increases. It is also found that the normalized equilibrium scour depth, as well as the normalized scour radius, decrease with the increasing Re. An empirical equation of the equilibrium scour depth is derived as a function of Reynolds number based on the experimental results so as to better account for Re effect in the scour design.

Effect of flow deflectors on local scour around artificial reefs under steady current: Experimental and numerical investigations

Local scour around two pipelines in tandem in steady current

Experimental study of local scour around subsea caissons in steady currents

3D numerical modelling of scour around a jacket structure with dynamic free surface capturing

A three-dimensional numerical model is established for simulating scour propagation in spanwise direction under a sub-sea pipeline in steady currents. In the model, flow is simulated by solving the Reynolds averaged Navier-Stokes equations with a k-Z turbulence model. The bed development is modelled by conservation of sediment mass. Calculations are carried to simulate local scour development below a pipeline that has been investigated experimentally. The input conditions of the simulation are set as closely as possible to those used in the physical tests reported in literature. The embedment depth of the pipeline was 0.2 pipeline diameter. It was found that scour development in the spanwise direction is mainly caused by the flow velocity around the span shoulders, where the gap between pipeline and bed is small. In the middle of the scour hole, the scour process is similar to that observed in the 2D laboratory tests and 2D numerical results reported in previous studies. The simulation demonstrates the capability of the 3D model although the calculated propagation speed of scour hole in the spanwise direction of pipeline is slightly lower than that measured in the tests.

Three-dimensional Computational Fluid Dynamics modelling of scour around a single pile due to combined action of the waves and current using Level-Set method