Numerical Modeling of Flow and Local Scour around Pipeline in Steady Currents Using Moving Mesh with Masked Elements

This work reports on a computational fluid dynamics (CFD) model for flow and local scour around a pipeline in steady currents that uses a mixed moving-mesh and fixed-grid method. It performs mesh motions for bed conforming without considering the pipeline and then simulates the pipeline with a fixed-grid approach after the mesh motion process has been completed. The proposed model combines the best properties of the boundary-fitted-grid and fixed-grid methods. In contrast to previous boundary-fitted-grid models, the present model uses masked elements to resolve the effects of a stationary object on the flow and sediment scour processes. This approach makes it possible to track directly the moving fluid-sediment interface using a very simple mesh setup, which is more practical for engineering computations than the existing models. The modeled results are compared to published laboratory measurements as well as to previous numerical predictions obtained by other models. The results show that the proposed model satisfactorily reproduces the features of the local scour observed in the experiments and thus can be a promising tool for modeling flow and sediment scour problems.