Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
Abstract 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. INTRODUCTION Tsunamis 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_cient 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)).
Sliding of Caisson Submitted to Water Wedge Impact: Analytical Calculation and CFD Verifications
Medina, M. Martin (Université de Pau et des Pays de l’Adour) | Abadie, S. (Université de Pau et des Pays de l’Adour) | Mokrani, C. (Federico Santa María Technical University) | Morichon, D. (Université de Pau et des Pays de l’Adour)
Abstract In this work, the impulsive stage of a wave impact on a vertical breakwater is modelled based on the analogy with a water wedge impact. Coupling between pressure along the wall and caisson displacement is neglected. The aim of the present paper is to briefly present the method and verify the uncoupling hypothesis using Navier-Stokes numerical simulations. The water wedge analogy allows us first to analyse the influence of the wedge interface inclination (45°, 60° and 80°) on the sliding. Considering an ideal case without friction and uplift force, caisson sliding motion is found to decrease with wedge angle. Conversely, the velocity acquired by the caisson increases with the wedge inclination. In the 45° case, we show that the sliding simulated with a Navier-Stokes model taking into account the flow/structure coupling is finally close to the one estimated with the analytical method developed in this study, therefore validating the decoupling hypothesis. Introduction Caisson sliding is the predominant cause of vertical breakwater failure based on historical case reviews (Oumeraci (1994) and Takahashi et al. (2001)). Takahashi et al. (1994) was among the firsts to propose a method to evaluate the displacement of a caisson submitted to wave impacts taking into account the impulsive pressure component. Recently, Cuomo et al. (2011) estimated the sliding caisson including the dynamic component. However, the literature review shows a gap in the understanding of the precise role of wave shape on caisson motion. Pressure signals generated by water wave impacts are typically characterized by two distinct phases: first, an impulsive component identified by a very high magnitude and a short duration followed by a slower one, mainly controlled by hydrostatic pressure. The existence of the impulsive component has been observed and detailed in many studies (e.g., Kirkgöz (1991), Cuomo et al. (2010)). In wave impact, the peak pressure strongly depends on the wave local free surface shape and its relative position with respect to the wall (e.g., Whillock (1987) or Kirkgöz (1991)).