THE COMPUTATION OF BED SHEAR IN A NUMERICAL MODEL

Abstract

Local morphological changes beneath pipelines originating from hydraulic conditions show variations which are on a relatively small scale compared to the water depth. A numerical model to compute these very local hydraulic conditions is essential for the study of scour problems as for example can occur with a submarine pipeline. A detailed computation of bed shear and turbulence characteristics is provided by the model presented in this paper. It has been used to obtain the sediment transport capacity along the bed near a pipeline. Although the bed shear is the leading parameter for the sediment transport a combination of the latter with an empirical bed load formula seems to result in a rather rigid schematization of the complex sediment transport for the presented examples of local scour. The computed bed changes include ripple development.