Tsunami-like Solitary Wave Research Articles

Numerical Investigation on the Interaction between a Tsunami-like Solitary Wave and a Monopile on a Sloping Sandy Seabed

Numerical Investigation on the Interaction between a Tsunami-like Solitary Wave and a Monopile on a Sloping Sandy Seabed

2DH Numerical Study of Solitary Wave Processes around an Idealized Reef-Fringed Island

In order to better understand the role of coral reefs around an isolated island in mitigating tsunami hazards, this study performed a horizontally two-dimensional (2DH) numerical study of tsunami-like solitary wave propagation and run-up around an idealized reef-fringed island. The shock-capturing Boussinesq wave model, the FUNWAVE-TVD is used in the present study and well-validated with existing experimental data for its robustness in predicting 2DH solitary wave processes around an island. Based on the validated model, the typical solitary propagation process around the reef-fringed island and the effects of morphological and hydrodynamic parameters on the maximum run-up heights were systematically investigated. It is found that coral reefs can effectively reduce maximum run-up heights around an isolated island. The reef flat’s water depth, reef flat width, and reef surface roughness are the main factors affecting maximum run-up heights around an island, while the fore-reef slope has little impact. For the idealized reef-fringed island in this study, sea-level rise will cause coral reefs to lose their protective capability on the lee side, and the presence of coral reefs may even enhance tsunami hazards around an island when the reef flat width is very narrow or coral bleaching happens.

Predicting tsunami-like solitary wave run-up over fringing reefs using the multi-layer perceptron neural network

Modeling of tsunami wave interaction with coral reefs to date focuses mainly on the process-based numerical models. In this study, an alternative machine learning technique based on the multi-layer perceptron neural network (MLP-NN) is introduced to predict the tsunami-like solitary wave run-up over fringing reefs. Two hydrodynamic forcings (incident wave height, reef-flat water level) and four reef morphologic features (reef width, fore-reef slope, beach slope, reef roughness) are selected as the input variables and wave run-up on the back-reef beach is assigned as the output variable. A validated numerical model based on the Boussinesq equations is applied to provide a dataset consisting of 4096 runs for MLP-NN training and testing. Results analyses show that the MLP-NN consisting of one hidden layer with ten hidden neurons provides the best predictions for the wave run-up. Subsequently, model performances in view of individual input variables are accessed via an analysis of the percentage errors of the predictions. Finally, a mean impact value analysis is also conducted to evaluate the relative importance of the input variables to the output variable. In general, the adopted MLP-NN has high predictive capability for wave run-up over the reef-lined coasts, and it is an alternative but more efficient tool for potential use in tsunami early warning system or risk assessment projects.

Simulation of a tsunami-like solitary wave interacting with a piled baffle penetrated breakwater

A piled baffle penetrated breakwater is a widely used free surface type breakwater that is prone to instabilities under extreme waves, such as tsunamis. The studies of interactions between the tsunami-like solitary waves and the piled baffle penetrated breakwaters are rare in the literature. In this paper, a modified mass source method is proposed to simulate interactions between a piled baffle penetrated breakwater and tsunami-like solitary waves. The modified mass source method has higher accuracy than the original mass source method in simulating highly non-linear waves and the accuracy of this method is not related to the shape of the source region. Based on the modified method a two-dimensional viscous numerical wave tank is constructed and validated from different aspects. Using the validated numerical model, simulations of interactions between tsunami-like solitary waves and the breakwater are performed. The surface elevation, pressure distribution and flow mechanics of the interaction are investigated in detail. Our findings will help to improve the understanding in the occurrences of tsunami-induced damages on the piled baffle penetrated breakwater and provide information for structural optimization designs.

A Numerical Investigation of the Reduction of Solitary Wave Runup by A Row of Vertical Slotted Piles

To improve the current understanding of the reduction of tsunami-like solitary wave runup by the pile breakwater on a sloping beach, we developed a 3D numerical wave tank based on the CFD tool OpenFOAM® in this study. The Navier-Stokes equations were applied to solve the two-phase incompressible flow, combined with an LES model to solve the turbulence and a VOF method to capture the free surface. The adopted model was firstly validated with existing empirical formulas for solitary wave runup on the slope without the pile structure. It is then validated using our new laboratory observations of the free surface elevation, the velocity and the pressure around a row of vertical slotted piles subjected to solitary waves, as well as the wave runup on the slope behind the piles. Subsequently, a set of numerical simulations were implemented to analyze the wave reflection, the wave transmission, and the shoreline runup with various offshore wave heights, offshore water depths, adjacent pile spaces and beach slopes. Finally, an improved empirical equation accounting for the maximum wave runup on the slope was proposed by taking the presence of the pile breakwater into consideration.

Large eddy simulation modeling of tsunami-like solitary wave processes over fringing reefs

Abstract. Many low-lying tropical and subtropical reef-fringed coasts are vulnerable to inundation during tsunami events. Hence accurate prediction of tsunami wave transformation and run-up over such reefs is a primary concern in the coastal management of hazard mitigation. To overcome the deficiencies of using depth-integrated models in modeling tsunami-like solitary waves interacting with fringing reefs, a three-dimensional (3-D) numerical wave tank based on the computational fluid dynamics (CFD) tool OpenFOAM® is developed in this study. The Navier–Stokes equations for two-phase incompressible flow are solved, using the large eddy simulation (LES) method for turbulence closure and the volume-of-fluid (VOF) method for tracking the free surface. The adopted model is firstly validated by two existing laboratory experiments with various wave conditions and reef configurations. The model is then applied to examine the impacts of varying reef morphologies (fore-reef slope, back-reef slope, lagoon width, reef-crest width) on the solitary wave run-up. The current and vortex evolutions associated with the breaking solitary wave around both the reef crest and the lagoon are also addressed via the numerical simulations.

Numerical Investigation of Sediment Transport of Sandy Beaches by a Tsunami-Like Solitary Wave Based on Navier–Stokes Equations

To improve our current understanding of tsunami-like solitary waves interacting with sandy beach, a nonlinear three-dimensional numerical model based on the computational fluid dynamics (CFD) tool OpenFOAM® is first self-developed to better describe the wave propagation, sediment transport, and the morphological responses of seabed during wave runup and drawdown. The finite volume method (FVM) is employed to discretize the governing equations of Navier–Stokes equations, combining with an improved volume of fluid (VOF) method to track the free surface and a k–ε model to resolve the turbulence. The computational capability of the hydrodynamics and the sediment transport module is well calibrated by laboratory data from different published references. The results verify that the present numerical model can satisfactorily reproduce the flow characteristics, and sediment transport processes under a tsunami-like solitary wave. The water-sediment transport module is then applied to investigate the effects of prominent factors, such as wave height, water depth, and beach slope, in affecting the beach profile change. Finally, a dimensionless empirical equation is proposed to describe the transport volume of onshore sediment based on simulation results, and some proper parameters are recommended through the regression. The results can be significantly helpful to evaluate the process of transported sediment by a tsunami event.

Consistent Particle Method simulation of solitary wave impinging on and overtopping a seawall

Tsunamis are among the most destructive natural hazards and can cause massive damage to the coastal communities. This paper presents a first numerical study on the tsunami-like solitary wave impinging and overtopping based on the mesh-free Consistent Particle Method (CPM). The distinct feature of CPM is that it computes the spatial derivatives in a way consistent with the Taylor series expansion and hence achieves good numerical consistency and accuracy. This largely alleviates the spurious pressure fluctuation that is a key issue for the particle method. Validated by the benchmark example of solitary wave impact on a seawall, the CPM model is shown to be able to capture the highly deformed breaking wave and the impact pressure associated with wave impinging and overtopping. Using the numerical model, a parametric study of the effect of seawall cross-sectional geometry on the characteristics of wave overtopping is conducted. It is found that a higher water level can lead to much more intensive overtopping volume and kinetic energy of the overtopping flow, which implies that the coastal areas are at higher risk as the sea level rises. For the purpose of engineering interest, a simple and practical way to estimate the intensity of a real tsunami is presented in terms of the volume and energy of the bulge part of the incident wave.

Towards a more complete tool for coastal engineering: solitary wave generation, propagation and breaking in an SPH-based model

ABSTRACTThe present work describes the implementation of an advanced solitary wave generation system in the mesh-less SPH-based DualSPHysics model to simulate tsunami-like solitary waves. Three different generation theories have been implemented and are extended to generate multiple solitary waves. The numerical model is validated against theoretical solutions and physical model results from three different experimental campaigns, which investigated respectively: i) the forces exerted on harbour protections; ii) the run-up of solitary waves on a gentle beach; and iii) the impact of double solitary waves on two cylindrical reservoirs. The differences of modelling breaking and non-breaking wave conditions are highlighted. The results demonstrate the capability of DualSPHysics to represents the main hydrodynamic properties of solitary waves when interacting with the shoreline or with coastal structures. The applicability of DualSPHysics to coastal engineering problems is enhanced, being the model already capable of generating monochromatic waves and random sea states.

The influence of climate change on tsunami-like solitary wave inundation over fringing reefs

ABSTRACTThe protective capability of fringing reefs against tsunami hazards has been reported in numerous post-disaster surveys. It is believed that global warming is changing the water level over the reef flat and reef surface roughness by sea-level rise and coral bleaching. For a better understanding of the influence of climate change on tsunami hazards over fringing reefs, this study utilized a shock-capturing Boussinesq wave model, FUNWAVE-TVD, to simulate the tsunami-like solitary wave propagation and run-up over fringing reefs. Calibrated and validated by the newly obtained experimental data, the present model with shock-capturing scheme, in which only the ratio of wave height to water depth is used to trigger wave breaking, shows reasonable prediction of solitary wave transformation and run-up height over sharply varying reef bathymetry. Numerical experiments were then carried out to investigate the effects of sea-level rise and degrading of the reef surface roughness on the solitary wave inundation distance and fluid force distribution in the inundation zone. Numerical results clearly demonstrate how tsunami hazards change within the inundation zone in response to higher water levels and lower reef roughness and suggest climate change, especially sea-level rise, will significantly increase tsunami hazards in the low-lying areas of the reef-lined coasts. Presented results are discussed for the effects of sea-level rise and coral bleaching on the solitary wave process and implications to further improve the resilience under the threat of climate change.

Simulation on tsunami-like solitary wave run-up around a conical island using a modified mass source method

Predicting the maximum run-up height and inundated area caused by tsunami events has been a hotly debated topic recently. Nevertheless, the wave height-to-depth ratios (nonlinearity) adapted previously tended to be conservative, considering the fact that a tsunami wave is an extreme wave condition with large wave height. In the present study, a mass source wave-generating approach for highly nonlinear waves is presented using our in-house solver, DUT-FOAM, which is a hydrodynamic solver developed using the open source code library OpenFOAM. By fully considering the mass output from the source region, a more reasonable mass source function has been obtained to compensate for the inadequacy of original method in simulating highly nonlinear waves. A newly designed numerical wave tank is performed for different nonlinearities. Numerical simulations of tsunami wave propagating to a conical island are carried. Fairly good agreements are obtained from the qualitative and quantitative comparisons between numerical results (Liu, Cho, Briggs, Kanoglu, & Synolakis, 1995) and laboratory data (Briggs, Synolakis, Harkins, & Green, 1995) regarding run-up maps around the island. The comparison reveals that present model offers a fast and accurate way to simulate highly nonlinear waves and is potentially useful and efficient for forecasting the run-up heights.

Numerical investigation of solitary wave interaction with a row of vertical slotted piles on a sloping beach

To improve our current understanding of tsunami-like solitary waves interacting with a row of vertical slotted piles on a sloping beach, a 3D numerical wave tank based on the CFD tool OpenFOAM® was developed in this study. The Navier-Stokes equations were employed to solve the two-phase incompressible flow, combining with an improved VOF method to track the free surface and a LES model to resolve the turbulence. The numerical model was firstly validated by our laboratory measurements of wave, flow and dynamic pressure around both a row of piles and a single pile on a slope subjected to solitary waves. Subsequently, a series of numerical experiments were conducted to analyze the breaking wave force in view of varying incident wave heights, offshore water depths, spaces between adjacent piles and beach slopes. Finally, a slamming coefficient was discussed to account for the breaking wave force impacting on the piles.

On-Bottom Stability Analysis of Cylinders under Tsunami-Like Solitary Waves

A two-dimensional (2D) laboratory investigation on the horizontal and vertical hydrodynamic forces induced by tsunami-like solitary waves on horizontal circular cylinders placed on a rigid sea bed is presented. A series of 30 physical model tests was conducted in the wave channel of the University of Calabria in which a rigid circular cylinder was equipped with 12 pressure transducers placed along its external surface to determine the wave loads, with three wave gauges to record the surface elevation. The observed experimental range was characterized by the prevalence of the inertia component for the horizontal forces and of the lift component for the vertical ones. On the basis of the performance of several time-domain methods, the wave loads and the undisturbed velocity and acceleration derived from the surface elevation of the cylinder section were used to calculate the drag, lift, and horizontal and vertical inertia coefficients in the practical Morison and transverse semi-empirical equations.

A study of tsunami-like solitary wave transformation and run-up over fringing reefs

After the 2004 Indian Ocean tsunami, the effectiveness of fringing reefs in protecting coastlines from tsunami-induced inundation has aroused great attention in the post-tsunami surveys. To better understand the role of fringing reefs in the mitigation of a tsunami hazard, laboratory experiments were conducted in a wave flume to study the transformation and run-up of tsunami-like solitary waves over various fringing reef profiles. The effects of incident wave height, reef-flat submergence, lagoon width and reef surface roughness were examined. Cylinder arrays were employed to create artificial roughness elements on the reef surface. Empirical formulas based on the experimental data were also proposed for the wave run-up. The ratio of the reef flat submergence to the incident wave height was always found to be the dominant parameter to characterize the wave run-ups over various tested reef profiles. Subsequently, a numerical model based on the improved Boussinesq equations including the drag effect of roughness elements was validated by the experimental data. The validated model was then applied to investigate the impacts of variations of reef morphologies (fore-reef slope, back-reef slope, reef-flat width, reef-crest width) on the solitary wave run-up.

On the soil response of a coastal sandy slope subjected to tsunami-like solitary wave

This study proposes a two-dimensional coupled approach to examine dynamic response of a sloping beach due to tsunami-like solitary wave. Wave motion is governed by Reynolds-averaged Navier–Stokes (RANS) equations, while the beach response is described with the poro-elastoplastic theory. The wave module and beach module are strongly integrated, resulting in a profound investigation of the solitary wave-induced soil response. Validation against the experimental demonstrates the applicability of the present approach. Results show that the excess pore water pressure ratio (EPWPR) is significant in the shallow soil. Distribution of EPWPR along the soil depth direction shows a decreasing trend. In addition, the principal axes of soil element on the shoreline rotated considerably under the solitary wave loading. When wave draws down from the slope, both shear stress and mean effective stress decrease compared with the run-up process. For engineering practice, special attention is given to the effect of permeability and coast slope on the soil response subjected to tsunami-like solitary waves.

HYDRODYNAMIC EFFICIENCY AND LOADING OF A TSUNAMI-FLOODING BARRIER (TFB)

The Tsunami-Flooding Barrier (TFB) is an impermeable vertical structure proposed at relatively large water depths, at which it is theorised that a tsunami will reach the structure before turning into a bore. The proposed hypothesis is tested in this study by means of a validated Computational Fluid Dynamics (CFD) model. The hydrodynamic efficiency of the impermeable TFB structure is confirmed and the effect of different aspects on the hydrodynamic efficiency of the structure are studied. These aspects include water depth, free board, surface roughness and the consideration of a deflecting parapet (named here as a surge stopper). Further, a new method is developed for calculating the tsunami-like solitary wave run-up and loads on the structure. The method is then compared to the Goda method for calculating storm wave loads on vertical impermeable structures. It is concluded that using the Goda method will severely underestimate the tsunami-like solitary wave load on the TFB structure.

Laboratory study on effects of submerged obstacles on tsunami wave and run-up

This paper presents laboratory experiments and numerical simulations of effects of submerged obstacles on tsunami-like solitary wave and its run-up. This study was carried out for the breaking and non-breaking solitary waves on 1:19.85 uniform slope which contains a submerged obstacle. New laboratory experiments are performed to describe the mitigation of tsunami amplitude and run-up under the effect of submerged obstacles. We are based on experimental results obtained to validate the numerical model. The numerical modeling using COULWAVE aims essentially to show the effect of the obstacle on the shape of solitary wave and the limit of this effect. Using a multiple nonlinear regression, we have determined a model to estimate height of run-up according to the amplitude of the wave and the obstacle peak depth.

Numerical Investigation of Tsunami-Like Solitary Wave Interaction with a Seawall

Seawall is a most commonly used structure in coastal areas to protect the landscape and coastal facilities. The studies of interactions between the tsunami-like solitary waves and the seawalls are relatively rare in the literature. In this study, a three-dimensional numerical model based on OpenFOAM® was developed to investigate the tsunami-like solitary waves propagating over a rectangular seawall. The Navier–Stokes equations for two-phase incompressible flow, combining with methods of [Formula: see text] for turbulence closure and Volume of Fluid (VOF) for tracking the free surface, were solved. Laboratory experiments were performed to measure some of the hydrodynamic feature associated with solitary waves. The model was then validated by the laboratory data, and good agreements were found for free surface, velocity and dynamic pressure around the seawall. Finally, a series of numerical experiments were conducted to analyze the evolution of both wave and flow fields, the overtopping discharge as well as wave pressure (force) around the seawall, special attention is given to the effects of seawall crest width. Our findings will help to improve the understanding in the occurrences of tsunami-induced damages in the vicinity of seawall such as wave impact and local scouring.

Numerical Modeling of Tsunami-Like Solitary Wave Impinging and Overtopping a Seawall through SPH Schemes by Considering the Effect of Entrapped Air

Numerical Modeling of Tsunami-Like Solitary Wave Impinging and Overtopping a Seawall through SPH Schemes by Considering the Effect of Entrapped Air In the current study, Tsunami-like solitary wave impinging and overtopping an impermeable seawall is numerically simulated. Tsunami-like solitary wave breaking has been considered before reaching an impermeable trapezoidal seawall of a particular slope. Smooth Particle Hydrodynamic (SPH) as a Lagrangian mesh-less method is implemented for the simulation purposes. In order to validate the numerical model, the obtained solitary wave profile is compared against existing experimental and analytical data and good compliance is displayed. Based on the computational results, high accordance is also achieved between the numerically found wave structure and the geometry of experimental waves. Furthermore, nature of breaking of Tsunami-like solitary wave and its overtopping on seawalls is examined. Comparison of these results against experimental data as well as water surface profiles by RANS method indicate greater consistency of SPH results with the experimental findings. Also, computational results related to time histories of dynamic pressure from SPH simulations are presented and compared with experimental data and numerical models, and good agreement is achieved for the peak pressure.

Simulation of Nearshore Tsunami Breaking by Smoothed Particle Hydrodynamics Method

AbstractThis study applies the numerical model GPUSPH, an implementation of the weakly compressible smoothed particle hydrodynamics (SPH) method on graphics processing units, to simulate nearshore tsunami processes. Two sets of laboratory experiments that involve violent wave breaking are simulated by the three-dimensional numerical model. The first set of experiments addresses tsunamilike solitary wave breaking on and overtopping an impermeable seawall. Comparison with free-surface profiles and laboratory images shows that GPUSPH satisfactorily reproduces the complicated wave processes involving wave plunging, collapsing, splash-up, and overtopping. The other set of experiments investigates tsunamilike solitary wave breaking and inundation over shallow water reefs. The performance of GPUSPH is evaluated by comparing its results with (1) experimental data including free-surface measurements and cross-shore velocity profiles, and (2) published numerical results obtained in two mesh-based wave models: the n...