Sriram Venkatachalam

The paper presents coupling between a mesh-based finite-element model for Boussinesq equations (FEBOUSS Agarwal et al., 2022) with a meshless local Petrov–Galerkin model for the Navier–Stokes equations (MLPG_R Agarwal et al., 2021) in 3D. Boussinesq equation models are widely used for simulating wave-propagation over large domains with uneven topography using a 2D surface mesh. Mesh-less models inherently capture large free-surface deformations and have shown promise in simulating wave-structure interaction, run-up and breaking phenomenon. The hybrid approach in this paper assumes a 3D MLPG_R sub-domain surrounded by the 2D mesh of FEBOUSS. The coupling interface in MLPG_R consists of relaxation zones that can be placed along multiple boundaries of the sub-domain for exchanging particle velocity from FEBOUSS. This hybrid model is therefore capable of simulating directional waves, that has not been reported previously. The paper first presents the procedure for calculating the depth-resolved velocities in 3D from the Boussinesq model. The resultant velocities are compared against theory, experiments and other models. The following sections present the coupling algorithm along a single and multiple coupling interfaces in MLPG_R. Validation results for this hybrid model are provided using surface elevation and velocity measurements for regular waves, including directional cases. In general, the results from the hybrid model are reported to have marginal over-prediction of peaks compared to purely MLPG_R simulation. Finally, the interaction of a vertical cylinder with direction regular wave is simulated using the 3D hybrid model.

The estimation of the sediment flux due to individual ship movement is necessary to identify adverse effects on the river banks in tidally-driven waterways. The separation of each wake event due to ship propagation from the tides is cumbersome. The present study focuses on the study of the ship waves on the sediment resuspension in intertidal waterways through a field survey. The time–frequency analysis proved to be an effective tool for separating the high-frequency ship waves from the tides. The ship-generated SSC was estimated by using the backscattering intensity from the acoustic sensors after proper calibration. The individual effect of each ship wake event on the sediment resuspension was estimated by filtering the ship-generated SSC from the total SSC by using a moving average filter. The overall contribution of the ship waves during the survey tenure was 24.66% with respect to the ambient SSC. The approximate amount of sediment flux by ship waves in a calendar year could be 1.46∗106g/m2. Finally, a new empirical equation to predict the sediment flux from the depth Froude number is proposed, which could be used in long-term analysis of SSC after proper calibration and validation.

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.

This study investigates the wave-vegetation interaction of elongated solitary waves and solitary waves. The energy reduction offered by the vegetation from the elongated solitary waves and solitary waves considering them as extreme events like storm surge and tsunami, has been studied. The energy contained in elongated solitary waves and solitary waves were estimated using the spectral density method. Due to longer period, the energy contained by an elongated solitary wave will be higher than the solitary wave for the same H/d ratio. However, the wave energy reduction percentage of elongated waves was the same as that of solitary waves passing over the vegetation belt. The maximum energy reduction observed through this experiment is about 25%. The attenuation characteristics of the waves were observed to be influenced by submergence ratio, relative vegetation width, and steepness ratio on the incident wave. In this study, a modified submergence ratio has been proposed considering the flow characteristics of the waves passing over the vegetation. This was proposed based on the observations from the experimental study on wave attenuation characteristics, and considering the results from the previous literature. An empirical equation for estimating the wave height attenuation depending on the above-mentioned dimensionless parameters are proposed based on multivariate nonlinear regression analysis.

This paper presents the application of Improved Meshless Local Petrov Galerkin method with Rankine source for wave interaction with vegetation model. The mathematical model is based on the unified governing equation, incorporating both pure fluid and vegetation regions. The governing equation consists of additional force terms such as the resistance given by vegetation. This additional force term derived from Morison's equation, where the vegetation is assumed to be a series of cylinders or strips. The drag force term for strip/square type vegetation is reported in the present study. The interface between fluid and vegetation region has a smooth variation of porous rate using transition zone to avoid discontinuity. The model is validated using the available experimental results. The validated model is applied for finding out the effective shape of vegetation and the influence of vegetation patch in dissipating the wave energy from solitary waves.

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.

The following sections are included: Introduction Equations of Motion Case Studies and Solutions Summary References.

This paper presents a 2D/3D hybrid numerical model for studying the interaction of non-breaking waves with cylindrical structure. The work combines the strengths of mesh-based and particle-based methods, where the wave propagation is solved using 2D mesh-based potential theory model and the interaction with the structure is solved using 3D particle-based Navier-Stokes model. The paper presents the formulation of the two models and the weak-coupling methodology, along with recent improvements in the 3D MLPG R (Mesh-less Petrov-Galerkin based on Rankine source solution) particle based method. The numerical results from interaction of fixed cylinder with solitary and focussed waves are compared with experimental data. The work demonstrates a significant reduction in simulation time for wave-structure interaction problems achieved using this hybrid approach without compromising on accuracy.

The following sections are included: Introduction Causes of a Tsunami Tsunami Earthquakes Tsunami due to Volcano Appearance of a Tsunami Wave Tsunami Characteristics Tsunami Transformation Occurrence of Recent Devastating Tsunamis Tsunami Warning System. Summary References.

A finite element model for depth integrated form of Boussinesq equations is presented. The equations are solved on an unstructured triangular mesh using standard Galerkin method with mixed interpolation scheme. The elemental integrals are calculated analytically and time-stepping is done using Runge–Kutta 4th order method. It is extended to simulate ship-generated waves using moving pressure fields. The unstructured formulation provides the flexibility of mesh refinement as needed, for capturing wave transformation or moving pressure field. The model is verified against experimental and numerical results for wave transformation over the Whalin shoal. The results for moving pressure field are compared against numerical results from FUNWAVE. Further, a simulation of ship navigating a curved path is presented. Finally, a real-life application and validation against field measurements is provided for waves generated by a fast ferry moving along a GPS tracked path in Tallinn Bay, Estonia.