Numerical Modeling of Wave and Current Induced Scour

Abstract

This thesis investigates local scour around a vertical pile under steady current and regular waves using the REEF3D::CFD solver. The model couples RANS (k–ω), a level-set free surface, and a morphodynamic sediment module. Validation is performed against two benchmarks: scour under current and scour under waves. The aims are to reproduce the time history and near-equilibrium scour depth, quantify grid needs, and assess a reduced-length numerical wave tank (NWT). Under current, simulations match the observed growth and final profile; a near-bed spacing of about 0.75 cm is adequate. Under waves, both a 28m and a 4.4m NWT are tested; dx = 0.02m gives the best wave quality. The reduced tank reproduces S/D(t) and the final depth with comparable accuracy at much lower cost. A Keulegan–Carpenter study (KC = 3, 6.5, 18) shows that larger KC accelerates early scour and deepens the near-equilibrium hole, with signs of saturation at high KC. Overall, REEF3D gives credible predictions, and the short NWT enables efficient parametric studies.