Now showing 1 - 8 of 8
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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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    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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    An interactive CAD solution for flexural members
    Now-a-days, computers are being widely used in the design of flexural members. Various software have been created for this purpose. All these software give the final design results only. This can be useful to check whether the design is safe. But, the steps involved in calculations are also necessary as it is in manual design. Software catering to this need becomes essential. Thus, a chance may be given to the users to validate the program and also to change the design requirements as per specifications. In addition, there are two spin-offs. The software can be used as a pedagogical tool for students and gives engineers a sense of familiarity with the software tool.
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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).
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    Simulation of nonlinear free surface dispersive shallow water waves
    The two-dimensional time domain simulation of nonlinear waves has received considerable attention in the recent years, in which a mixed Eulerian and Lagrangian method (MEL) shows potential application. In this paper, the finite element method is used in the domain for the estimation of the velocity potential, while, a cubic spline approximation is used to recover the velocity. The present methodology has been compared with the laboratory simulation of a Cnoidal wave over a long time far away from the wave making boundary. The present numerical model is further extended to investigate the interactions with the submerged obstacles. This reveals that by using the present methodology, the dispersive characteristics are not predicted well, compared, to the experimental measurements for very steep waves. Further modification is carried out for the velocity recovery by using least square method to overcome the difficulties in the simulation of steep waves. Smoothing or regridding is not applied in the simulation unlike in most of the existing simulation. © 2007 International Association for Hydraulic Engineering and Research, Asia Pacific Division.
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    Numerical simulation of 2D sloshing waves due to horizontal and vertical random excitation
    The motion of sloshing waves under random excitation in the sway and heave modes have been simulated in a numerical wave tank. The fully nonlinear wave is numerically simulated using the finite element method with the cubic spline and finite difference approximations, in which the need for smoothing and regridding is minimal. The present model predictions are compared with that of Frandsen [Frandsen JB. Sloshing motions in the excited tanks. J Comput Phys 2004;196:53-87] for the regular wave excitation in the vertical and horizontal modes. The sloshing due to the simulated random excitation with different peak frequencies relative to the natural sloshing frequency has been subjected to frequency domain analysis. The results showed that irrespective of peak excitation frequency, the peaks appear at the natural frequencies of the system and the peak magnitude appears close to the natural frequency for the sway excitation. The higher magnitude is seen when the excitation frequency is equal to the first mode of natural frequency, due to the resonance condition. In the case of heave excitation, even though the peaks appear at the natural frequencies, the magnitude of the spectral peak remains the same for different excitation frequencies. © 2006 Elsevier Ltd. All rights reserved.
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    Experimental and numerical studies on the tsunami wave characteristics
    The devastating effects of the great Indian ocean tsunami has forced researchers in focusing their attention more vigorously on understanding the behaviour during its propagation and its effects on structures. This can obviously be accomplished through numerical and physical model studies or combination of both. The characteristics of a tsunami wave can approximately be same as that of a solitary wave which is basically a shallow water wave. Hence, the studies on the characteristics of shallow water waves have become an emerging topic of interest. An important aspect of a mitigation effort is to predict the tsunami wave kinematics. A combination of experimental and numerical simulation of tsunami represented by the solitary wave was studied and their comparison is discussed in this paper. The details of the numerical approach, methodology, instrumentation and measurement adopted for the present study are reported. The disagreement of the experimental simulation of solitary wave elevations with that of numerical simulation has been addressed and the possible discrepancies are overcome, the procedure of which are briefly discussed. The dynamics of the tsunami wave propagation over an uneven topography is studied using the developed numerical model. © 2007 Taylor & Francis Group, LLC.