Faculty Publications
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Item Hydroelastic analysis of articulated floating elastic plate based on Timoshenko–Mindlin plate theory(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2018) Praveen, P.; Karmakar, D.; Guedes Soares, C.G.The wave interaction with articulated floating elastic plate is investigated considering the Timoshenko–Mindlin thick plate theory for both finite and shallow water depths. The elastic plates are modelled as finite flexible floating structure interconnected with vertical linear/rotational spring stiffness. The eigenfunction expansion method along with the orthogonal mode-coupling relation is used to analyse the hydrodynamic behaviour of the interconnected structure. The study is performed for different articulated edge conditions for varying plate thickness and water depths to understand the behaviour of articulation under the action of an ocean wave. The hydroelastic response of the interconnected floating elastic plate with different connector stiffness is observed to compare well with the result available in the literature. The present study provides an insight into the effect of articulated joints with varying spring stiffness for the suitable design of the structure. © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group.Item Wave Interaction With Floating Elastic Plate Based on the Timoshenko-Mindlin Plate Theory(American Society of Mechanical Engineers (ASME) infocentral@asme.org, 2019) Praveen, K.M.; Karmakar, D.; Guedes Soares, C.In the present study, the wave interaction with the very large floating structures (VLFSs) is analyzed considering the small amplitude wave theory. The VLFS is modeled as a 2D floating elastic plate with infinite width based on Timoshenko-Mindlin plate theory. The eigenfunction expansion method along with mode-coupling relation is used to analyze the hydroelastic behavior of VLFSs in finite water depth. The contour plots for the plate covered dispersion relation are presented to illustrate the complexity in the roots of the dispersion relation. The wave scattering behavior in the form of reflection and transmission coefficients are studied in detail. The hydroelastic performance of the elastic plate interacting with the ocean wave is analyzed for deflection, strain, bending moment, and shear force along the elastic plate. Further, the study is extended for shallow water approximation, and the results are compared for both Timoshenko-Mindlin plate theory and Kirchhoff's plate theory. The significance and importance of rotary inertia and shear deformation in analyzing the hydroelastic characteristics of VLFSs are presented. The study will be helpful for scientists and engineers in the design and analysis of the VLFSs. © 2019 by ASME.Item Hydroelastic analysis of periodic arrays of multiple articulated floating elastic plate(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2020) Praveen, K.M.; Karmakar, D.; Guedes Soares, C.The periodic array of multiple articulated floating elastic plate acted upon by ocean waves is analysed considering Timoshenko-Mindlin plate theory. The floating elastic plate is placed periodically and is interconnected with vertical linear and flexural rotational springs which acts as an articulated joint. The hydroelastic behaviour of multiple articulated floating elastic plate is analysed based on eigenfunction expansion method along with the orthogonal mode-coupling relation in finite water depth and the continuity of energy and mass flux are used in the hydroelastic analysis of floating plate at shallow water depth. Further, the application of the wide-spacing approximation (WSA) method is employed to analyse the hydroelastic characteristics of the multiple articulated floating elastic plate. The results obtained using the eigenfunction expansion method is compared with the results based on WSA at finite water depth and validated with the results available in the literature. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group.Item Gravity wave trapping by series of horizontally stratified wave absorbers away from seawall(American Society of Mechanical Engineers (ASME), 2020) Venkateswarlu, V.; Karmakar, D.The fluid oscillation between the rigid wall and stratified wave absorber is analyzed in the context of the linearized water wave theory. The stratified wave absorber is composed of multiple horizontal layers considering higher porosity in the surface layer, moderate porosity in the middle layer, and zero porosity in the bottom layer. The study examined the wave motion through multiple horizontally stratified wave absorbers on solving the multilayer dispersion relation. The eigenfunction expansion method is used to form the system of analytical equations using the property of orthogonal mode-coupling relation with continuity of dynamic pressure and velocity at each of the interfaces. The free spacing available between leeward porous wave absorber and the rigid wall is termed as “trapping chamber.” The effect of the trapping chamber on wave reflection and fluid force experienced by a rigid wall is discussed. The analytical results formulated for the physical problem are validated with the available experimental and numerical results. The wave trapping is examined and compared for three types of seawalls such as vertical wall, permeable wall, and stepped wall. The change in trapping chamber length shows the harmonic peaks and troughs in the trapping coefficients and the harmonic oscillations help in the design and development of the stratified porous wave absorbers for the protection of marine infrastructure. © © 2020 by ASMEItem Numerical investigation on the wave dissipating performance due to multiple porous structures(Taylor and Francis Ltd., 2021) Venkateswarlu, V.; Karmakar, D.Gravity wave interaction with porous structures is investigated under the assumption of linearized wave theory. Multiple porous blocks of finite thickness with finite spacing are investigated under the action of oblique ocean waves considering leeward unbounded region and confined region. The eigenfunction expansion method is employed to analyse the effect of multiple-confined regions in the trapping of oblique waves. The study outcomes are validated with numerical and experimental results available in the literature. The friction factor and the inertia effect of the porous medium are considered and different porosity conditions are adopted to determine the wave reflection coefficient, transmission coefficient, wave dissipation and wave force impact on the leeward wall. The functional efficiency of multiple fully extended porous structures is studied for different values of porosity, water chamber length, angle of incidence, friction factor and spacing between the porous blocks. The seabed is assumed to be uniform impermeable bottom and uneven bottom (step approximation is adopted). The study demonstrates that the better wave blocking is achieved with the increase in the series of porous structures and the confined regions can be used effectively for the trapping of oblique waves. The present study will be helpful in the design of porous structures for security of coastal facilities and coastal structures in offshore environment. © 2019 Indian Society for Hydraulics.Item Wave attenuation due to stratified porous structure in the presence of stepped seabed(Springer Nature, 2024) Varghese, A.; Krishna, K.R.A.; Karmakar, D.The wave transformation due to the stratified porous structures in the presence of stepped seabed at leeward side is analysed based on the small amplitude wave theory. The study is performed to analyse the effectiveness of both horizontal and vertical stratified porous structure for the wave attenuation in the nearshore regions using orthogonal mode-coupling relation and eigenfunction expansion method. The hydrodynamic coefficients such as wave reflection, transmission, dissipation, wave force acting and surface elevation are investigated for both horizontally and vertically stratified porous structures. The effect of change in the structural properties such as varying porosity, friction factor, structural width, angle of incidence and length between the porous structure and stepped seabed are examined. Thereafter, the comparative study is performed for both horizontally and vertically stratified porous structure in the presence of stepped seabed and the numerical results are validated with the results available in the literature. The present study illustrates that with the increase in step height, the wave damping efficiency is enhanced. In addition, the wave energy dissipation is observed more for horizontally stratified structure in the case of longer waves whereas vertically stratified structure is effective in dampening of shorter waves. Further, the wave reflection and transmission for vertically stratified structure is found to be more for same length between structure and stepped seabed. The stepped seabed in leeward side in combination with vertical and horizontal stratified porous structure is intended to be an effective solution for protection of coastal facility. © The Author(s), under exclusive licence to Sociedade Brasileira de Engenharia Naval 2024.Item Effect of seabed condition on the hydrodynamic performance of a pile-restrained H-shaped floating breakwater(Taylor and Francis Ltd., 2025) Panda, A.; Karmakar, D.; Rao, M.The present study investigates the hydrodynamic analysis of pile-restrained H-shaped porous breakwater for various seabed conditions using the small amplitude wave theory. The Multi-Domain Boundary Element Method (MDBEM) is employed to investigate the influence of parametric variations on the hydrodynamic coefficients and horizontal wave force under normal and oblique incident waves. The numerical accuracy is ensured by comparing it with the available literature. The numerical investigation on the hydrodynamic performance of the H-shaped breakwater is performed for various seabed configurations considering different angles of slope, the width of slope/step/obstacle, step height, number of steps, soil permeability, angle of wave incidence, the width of flange and submergence draft of the web of the H-shaped structure. The findings indicate that the seabed undulation has a higher wave impact on the breakwater than the horizontal seabed. In addition, the study suggests that the sloped seabed is preferable in deeper water depths to reflect waves efficiently and the seabed permeability can affect the hydrodynamic coefficients in shallow and intermediate water depths. The study performed on the H-shaped breakwater for varying seabed topography will be helpful in the design and construction of a suitable H-shaped breakwater for an effective wave absorber in coastal regions. © 2025 Informa UK Limited, trading as Taylor & Francis Group.Item Hydrodynamic performance of a hybrid floating breakwater-wave energy conversion system(SAGE Publications Ltd, 2025) Patil, S.B.; Karmakar, D.The study presents the hydrodynamic performance and wave energy conversion of a hybrid floating breakwater under the framework of small amplitude linear wave theory. The hybrid floating breakwater is composed of a partially liquid-filled rectangular-box type tank with built-in buoys connected to a Power Take-Off (PTO) (linear inductance generator) and is excited under regular wave conditions for (a) constrained roll motion, and (b) constrained surge, heave, and roll motion. The Boundary Element Method (BEM) is employed with the assumption of modest sloshing in the tank of the hybrid floating breakwater to estimate the hydrodynamic efficiency of the hybrid floating breakwater. Further, the experimental investigation on the Wave Energy Converter (WEC) capabilities and the hydrodynamic coefficients (wave reflection and transmission coefficients) are estimated for the excitation frequencies corresponding to nondimensional wavenumber. The present study reveals that the hybrid concept improves wave attenuation performance by 20%–35% compared to conventional floating breakwaters by increasing wave attenuation, damping and stabilizing the wave transmission coefficient (Formula presented) within (Formula presented). The experimental investigation shows that hybrid floating breakwater attaints its floating stability for the depth 15 – 25% of partially filled fluid for which the proposed design as floating breakwater as well as WEC system is achieved for a wide range of excitation frequencies. Furthermore, the hybrid floating breakwater functions as a barrier which is noted to be capable of significantly attenuating incoming progressive waves below the predetermined threshold values of wave attenuation characteristics, in addition to converting wave energy. © IMechE 2025. This article is distributed under the terms of the Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by/4.0/) which permits any use, reproduction and distribution of the work without further permission provided the original work is attributed as specified on the SAGE and Open Access page (https://us.sagepub.com/en-us/nam/open-access-at-sage).