Numerical Simulation of Tsunami Flooding Downstream a Quay Wall
Résumé
In this paper, the interaction of a tsunami and a quay wall is studied numerically with focus on the water volume flooding the downstream part of the quay. The model solves the Navier-Stokes equations using the VOF method. It is first validated on two cases close to the study configuration. Then flooding discharge are calculated considering two wave inputs (solitary wave, break flow over wet bottom) and increasing amplitudes. The differences are significant. The solitary wave give a short duration flooding due to its dependency between amplitude and frequency. The dam break flow produces flooding bursts followed by a steady residual flooding which may be the parameter of importance in this problem.INTRODUCTIONTsunamis are long waves whose destructive power has been illustrated in several dramatic recent events (e.g., the Tohoku tsunami in 2011). Vertical walls, designed for tsunami protection (i.e., tsunami seawall) or for other purpose (e.g., harbor quay wall) are known to be e\ₓient structures able to reduce tsunami impact inland by reflecting wave energy o\₋shore instead of allowing the whole wave energy transfer by run-up like beaches. However, depending on tsunami features, part of the wave may spill over the wall.The problem has already been studied in several papers. Fukui et al. (1963) and Shi-igai and Kono (1970) used quasi steady formulation of the flow over a weir to approach the overtopping volume. Iwasaki and Togashi (1968) studied the transformation of tsunami waves at a vertical quay wall using U-C characteristics in shallow water theory. Applications were made using solitary wave input signal. Ozhan and Yalciner (2011) applied the weir analogy to study the overtopping of solitary wave above vertical wall.More recently, Hsiao and Lin (2010) studied the overtopping of a solitary wave over a sloping seawall experimentally and by RANS modeling. Mizutani and Nakamura (2011) carried out an equivalent study but based on a half sinusoidal long wave and with a vertical quay wall. Baldock et al. (2012) studied the overtopping of solitary tsunami bore on sloped structure. Interaction between bores and vertical walls was more specifically studied in the context of loading determination (e.g., Togashi (1986)).