Modelling of Flow and Scour Around a Pipeline

A preliminary investigation of scour around a horizontal cylinder is presented in this paper. A coupled computational fluid dynamics and sediment transport model, FLOW-3D, was used to model the velocity around five static bed profiles, and the dynamic scour around a cylinder. Laboratory data from Jensen et al. (1990) was used to evaluate the modelled bed velocity. Comparisons are reasonable, although the bed velocity in the region of the cylinder is under-predicted. Modelled scour evolution were then compared with laboratory data from Mao (1986). The model predicted the general size and shape of the scour hole however there was an over-prediction in the length of the equilibrium scour hole. The dune created downstream of the cylinder is more prevalent than is present in the laboratory data. The model also overscoured upstream of the cylinder. Time scale to reach equilibrium was found to be on the order of 50 times shorter than the laboratory results.