Numerical Modelling of Bed Shear Stress in OpenFOAM

Abstract

In coastal zones, erosion is the major threat to the livelihood as it leads to the water inundation into the human premises. Sediment transport results in erosions causes morphological changes and also affects the coastal ecosystem. The sediment transport processes are primarily driven by bed shear stress induced by waves and currents. As bed shear stress plays a major role in the determining sediment transport rates, the accuracy of sediment transport models mainly rely on the basis of bed shear stress measurements. So, there is a need to measure the reliable bed shear stress to improve the effectiveness of sediment transport models. In coastal zones when the waves enter into the low water depth, it starts to feel the bottom and the effect of shear stress at the bottom will be high. In this paper, bed shear stress is estimated from the numerical simulations using OpenFOAM. In OpenFOAM, bed shear stress is calculated from viscous force on the bed by integrating the pressure and the skin frictional forces. Surface elevation and flow velocity were measured using the numerical gauges. This bed shear stress can be directly incorporated into the shields parameter. In this study, numerical simulations in OpenFOAM were carried out for the regular sinusoidal waves with a time step of 0.001 s for a total duration of 16 s. OpenFOAM uses the waves2Foam toolbox for wave generation in the numerical wave tank.