Christou, A; Stoesser, T; Pan, S; Yan, S; Xie, Z; (2023) Large eddy simulations of waves propagating over a submerged rectangular step in shallow water depths. In: Proceedings of the Thirty-third (2023) International Ocean and Polar Engineering Conference. (pp. pp. 2794-2800). International Society of Offshore and Polar Engineers (ISOPE): Ottawa, Canada.

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Abstract

In this study, the Large Eddy Simulation (LES) methodology is employed to investigate the interaction of waves with a submerged step and study the local flow hydrodynamics involved. First, the in-house LES Numerical Wave Tank (NWT) is used to simulate a previous laboratory study of cnoidal waves propagating over a submerged step and results of water surface elevations are used to evaluate the accuracy of the code. The study is then extended to report the flow physics involved and quantify the turbulent flow using plots of the vortex shedding using the Qcriterion. Additionally, the evolution of the water surface, in terms of the Level Set Method (LSM) signed distance function ϕ, is plotted in several time instances over one wave period and the interaction of flow structures with the submerged step and the water surface is reported and discussed. Additionally, in order to study the effect of the step’s geometry further simulations are conducted by varying the submergence depth and comparisons of the water-surface fluctuations and turbulent flow structures are made between different cases. Although the cases reported here are characterized as a two-dimensional problem, results suggest that three-dimensional effects also exist. For example, discontinuous and non-uniform large energetic eddies observed near the leading and trailing edge, as well as the formation of smaller vortices extending from the floor bed to the water surface, suggest that the three-dimensionality is critical in such applications and needs to be taken into account. Overall, results confirm the accuracy of the present NWT and show the complexity of the flow in such structures under the action of periodic waves in shallow water depths.

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