Now showing 1 - 10 of 29
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    2D nonlinear wave body interaction using Semi-ALE
    The present study aims at generating the fully nonlinear waves based on Finite Element method (FEM) used by SRIRAM et al. (2006). The author simulated the nonlinear waves based on structured mesh by regenerating the mesh at each and every time step using the Mixed Eulerian and Lagrangian (MEL) scheme. In this paper, it has been extended to unstructured mesh. The mesh is adapted at each and every time step by using the spring analogy method instead of regenerating at every time step which makes the above method called as Semi- Arbitary Lagrangian and Eulerian (Semi-ALE/SALE). The simulation has been carried out in a numerical wave tank (NWT) with a surface piercing rectangular object. For such a situation, the diffraction by a surface piercing object becomes relevant in connection to breakwater studies where the primary interest is wave reflection and wave transmission. Regular waves and solitary waves are generated from one end of the tank. The nonlinear wave reflection and transmission characteristics reveals that the transmission is less for regular waves, while in the case of solitary waves the reflected energy is very small and the transmission is more.
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    Tsunami Detection
    The following sections are included: Introduction Tsunami Warning Detection of Tsunamis with Sea-Level Sensors Indian Tsunami Early Warning System (ITEWS) Experimental Studies Summary References.
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    A comprehensive review on structural tsunami countermeasures
    (01-09-2022)
    Oetjen, Jan
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    Reicherter, Klaus
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    Engel, Max
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    Schüttrumpf, Holger
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    Tsunamis pose a substantial threat to coastal communities around the globe. To counter their effects, several hard and soft mitigation measures are applied, the choice of which essentially depends on regional expectations, historical experiences and economic capabilities. These countermeasures encompass hard measures to physically prevent tsunami impacts such as different types of seawalls or offshore breakwaters, as well as soft measures such as long-term tsunami hazard assessment, tsunami education, evacuation plans, early-warning systems or coastal afforestation. Whist hard countermeasures generally aim at reducing the inundation level and distance, soft countermeasures focus mainly on enhanced resilience and decreased vulnerability or nature-based wave impact mitigation. In this paper, the efficacy of hard countermeasures is evaluated through a comprehensive literature review. The recent large-scale tsunami events facilitate the assessment of performance characteristics of countermeasures and related damaging processes by in-situ observations. An overview and comparison of such damages and dependencies are given and new approaches for mitigating tsunami impacts are presented.
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    Simulation of 2-D nonlinear waves using finite element method with cubic spline approximation
    The estimation of forces and responses due to the nonlinearities in ocean waves is vital in the design of offshore structures, as these forces and responses would result in the extreme loads. Simulation of such events in a laboratory is quite laborious. Even for the preparation of the driving signals for the wave boards, one needs to resort to numerical models. In order to achieve this task, the two-dimensional time domain nonlinear problem has received considerable attention in recent years, in which a mixed Eulerian and Lagrangian method (MEL) is being used. Most of the conventional methods need the free surface to be smoothed or regridded at a particular/every time step of the simulation due to Lagrangian characteristics of motion even for a short time. This would cause numerical diffusion of energy in the system after a long time. In order to minimize this effect, the present study aims at fitting the free surface using a cubic spline approximation with a finite element approach for discretizing the domain. By doing so, the requirement of smoothing/regridding becomes a minimum. The efficiency of the present simulation procedure is shown for the standing wave problem. The application of this method to the problem of sloshing and wave interaction with a submerged obstacle has been carried out. © 2006 Elsevier Ltd. All rights reserved.
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    NWF: Propagation of Tsunami and its Interaction with Continental Shelf and Vertical Wall
    In this article, tsunamis represented as solitary waves was simulated using the fully nonlinear free surface waves based on Finite Element method developed by Sriram et al. (2006). The split up of solitary wave while it propagates over the uneven bottom topography is successfully established. Wave transmission and reflection over a vertical step introduced in the bottom topography is in good agreement with the experimental results from Seabra-Santos et al. (1987). The wave transformation over a continental shelf with different smooth slopes reveals that the solitary wave reflection increases while the continental slope varies from flat to steep. The interaction of the solitary wave with a vertical wall for different wave steepness has been analysed. The reflected shape of the profile is in good agreement with the observation made by Fenton and Rienecker (1982) and an increase in wave celerity is observed.
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    Tsunami-Driven Debris and Its Impact
    The following sections are included: Introduction Outline of Damage Caused by Debris Different Types of Debris Boulders as Debris Research on Motion and Impact of Debris Guidelines for Debris Impact Loading Debris Modelling Physical Model Tests Summary References.
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    Tsunami Propagation Modelling
    The following sections are included: Introduction Equations of Motion Case Studies and Solutions Summary References.
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    Velocity calculation methods in finite element based mel formulation
    The simulation of nonlinear waves can be carried out by using the conventional methods like Finite Element Method (FEM), Boundary Element Method (BEM) based on Mixed Eulerian and Lagrangian (MEL) formulation. The simulation based on FEM has the advantages of extending the code easily to viscous flow and to three-dimensional (3D) tank with complex geometry. While adopting FEM, the derivatives are usually found from differentiating the shape function, which is the direct differentiation of the velocity potential. The approximation of velocity field thus obtained is inferior than the approximation of the velocity potential. In time-dependent problems, this play an important role. Thus, researchers have been focusing on obtaining the derivatives through different methods such as Global Projection, Local Finite Difference (FD), mapped FD, least square method or by using cubic spline approximation. The present chapter shows a detailed review of these methods for calculating the derivatives including the advantages and disadvantages in the context of simulation of nonlinear free surface waves using structured/unstructured FEM.
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    Preface
    (01-01-2021) ; ; ;
    Nowbuth, Manta Devi
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    Nonlinear wave structure interaction using finite element method based on spring analogy techniques
    (01-12-2009) ; ; ;
    Schlenkhoff, A.
    The simulation of interaction of nonlinear waves with structures has been investigated by several investigators adopting Boundary element Method (BEM) and Finite Element Method (FEM). In handling complex geometries using FEM, simulation with unstructured mesh is required. The two options that are available in handling unstructured mesh are: regenerating the mesh for each time step, requiring a higher computational cost and the mesh moving procedure widely used in solid mechanics. In this paper, the application of two different spring analogies (Vertex and Segment methods) on the simulation of nonlinear free surface waves and its interaction with a submerged structure is reported. The numerical method has been extended to generate solitary waves, the results of which have been compared with laboratory tests that include the wave kinematics using PIV measurements. Copyright © 2009 by The International Society of Offshore and Polar Engineers (ISOPE).