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Simulation d'un écoulement de jet de rive par une méthode VOF

Abstract : Dynamic processes occurring in the swash zone have a significant impact on the shore area evolution. Because of wave breaking, a significant part of the cross-shore sediment transport occurs in this zone, especially in the area where wave run-up and run-down take place. Up to the shore line, a comprehensive understanding is given by existing numerical models based on the non linear shallow water equations or the Boussinesq equations. The wave decay is well reproduced, but the subsequent modelling of the sediment transport requires a parameterisation of the friction coefficient on the sea bed. The results of RANS numerical simulations of a bore propagating on a sloping beach and resulting in a run-up/run-down phenomenon are presented. Numerical results are compared to the results of a laboratory experiment by Yeh et al. (1989). Numerical simulations were carried out using the AQUILON model. Two different methods of interface tracking are implemented in the model to compute the interface between fluids (VOF PLIC and VOF TVD). The eddy viscosity is computed using the V2F model (Durbin, 1991). We study the bore generated from a dam-break condition. Shortly after its generation the bore propagates over a sloping beach. The geometry considered for numerical simulations is the same as for the experiments by Yeh et al. (1989). The theory of Whitham (1958), predicts the collapse of the bore at the shoreline. The theory of Shen and Meyer (1963) is up to date the reference model of the run-up flow. The experimental results of Yeh et al. (1989) clearly show a different phenomenon. It is discussed in the present paper. We examined in more detail the properties which may distinguish the bore collapse phenomenon from the subsequent run-up down. The results of our simulation show that the theory of Whitham does describe with sufficient detail the mechanism of bore collapse, due to the inherent shortcomings of shallow water equations. The results of our simulation are used to describe the transition between bore collapse and run-up flow. We analyse the evolution in time of the shear stress applied on the bottom along the swash water layer. We observe that the bottom shear stress is much lower during run-down as compared to run-up. The flow is highly asymmetrical between run-up and run-down.
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Submitted on : Friday, March 12, 2010 - 5:26:51 PM
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Sylvain Mauriet. Simulation d'un écoulement de jet de rive par une méthode VOF. Sciences de l'ingénieur [physics]. Université de Pau et des Pays de l'Adour, 2009. Français. ⟨tel-00463578⟩

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