Two-Phase Flow Model on Oscillatory Sheet-Flow

Under stormy waves on a sandy beach, a movable flat bed may appear when ripples have been washed out. Studies of the sheet flow have received much attention recently because a large amount of sand is transported under such conditions. However, most of the existing studies on the sediment transport are dealing with the phenomena under small tractive forces because this is easily reproduced in a small wave tank. Until now, very little understanding has been obtained on the sheet flow phenomena. The present paper develops a numerical model to analyze the oscillatory sheet flow. The mathematical formulation based on fluid-sediment two-phase flow is performed by expanding models from a unidirectional flow into an oscillatory flow. The developed model predicts the velocity field, properties of friction, and sediment transport rate. The model is shown to describe existing experimental data for oscillatory sheet flow.