Faculty Publications

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Long-term response analysis of hybrid STLP-WEC offshore floating wind turbine
(Taylor and Francis Ltd., 2025) Rony, J.S.; Karmakar, D.
In the present study, time-domain response analysis of different configurations of a hybrid Submerged Tension Leg Platform (STLP) combined with a Point Absorber-type Wave Energy Converter (WEC) (STLPWEC) is performed using the aero-servo-hydro-elastic simulation. The study employs long-term analysis technique to predict the most probable values of motion amplitudes, and the forces and moments developed at the tower base for the hybrid STLP-WEC system under operational wind speed conditions of the 5 MW wind turbine. The long-term distribution is performed using short-term responses based on Rayleigh distribution and North Atlantic wave data. The performance of the offshore STLP-WEC system depends on both the transfer functions (translational and rotational motions) and the wave spectrum model. A comparative study of the long-term responses using JONSWAP spectrum model for different configurations of the hybrid STLP-WEC systems is performed, providing valuable insights for designing floating hybrid systems. © 2025 Informa UK Limited, trading as Taylor & Francis Group.
Hydroelastic analysis of VLFS integrated with porous floating box breakwater using multi-domain boundary element method
(Elsevier Ltd, 2025) Hemanth, S.; Karmakar, D.
The present study analyses the feasibility of integrating a Very Large Floating Structure (VLFS) with a porous floating box-type breakwater kept fixed in its position to analyze the hydroelastic responses within the integrated system based on linearized wave theory. The integrated VLFS-breakwater system, comprising the VLFS and the porous box-type breakwater assures in mitigating the structural effects induced by waves. The coupled Multi-Domain Boundary Element Method (MDBEM) and Finite Difference Method (FDM) are employed to investigate the performance of integrated VLFS-breakwater system. The computational framework employs the MDBEM to model the fluid domain and the floating breakwaters, while the VLFS is modeled using the FDM approach. The study considers three distinct relative positions of the VLFS integrated with a floating breakwater on (i) the leeside, (ii) the seaside, and (iii) on both leeside and seaside of the VLFS. The numerical study is performed based on thin-plate theory and small amplitude wave theory. The study corroborates its numerical findings with existing literature, supporting the validity of its methodology. The integrated system effectively reduces forces acting on the VLFS by absorbing the primary impact of waves. Consequently, the hydroelastic response of the VLFS is reduced, preserving its structural integrity and enhancing overall safety. The study signifies the importance of integrating the porous box-type breakwater with the VLFS. The importance of the orientation of the structure towards the sea waves, the porosity of the breakwater, the effect of relative spacing between the breakwater and VLFS and variations in hydrodynamic responses with respect to the placement of the floating breakwater are thoroughly discussed. The study performed will be helpful in the design and implementation of integrated VLFS-breakwater system, enhancing their robustness and safety in maritime environments. © 2024 Elsevier Ltd
Hydrodynamic analysis of U-shaped OWC with varying bottom profiles integrated with ?-breakwater
(SAGE Publications Ltd, 2025) Muduli, R.; Karmakar, D.
In the present study, the fixed U-OWC integrated with ?-shaped breakwater is analysed considering three different bottom profiles (straight, inclined, and curved) of the interior chamber of the U-OWC. The hydrodynamic performance is assessed based on the theoretical maximum efficiency, radiation susceptance and conductance, reflection, transmission and dissipation coefficients and force coefficient on the top lip wall of U-OWC and front face of breakwater. The influence of geometric variations such as width of U-channel, draft of U-OWC, draft and width of breakwater and distance between the two structures on the hydrodynamic performance is analysed using Boundary Element Method (BEM). The study depicts that the presence of a wider U-channel width impairs the energy conversion efficiency of the U-OWC and increasing the draft of the U-OWC improves the efficiency of the device. Further, changing the bottom profile of the internal chamber of U-OWC changes the natural frequency of the device without hampering the efficiency. In addition, as the distance between the two structures is increased, transmission of waves decreases. The influence of wave force on the breakwater is noted to be maximum when the leading U-OWC structure has a curved bottom. The study on the variation of the bottom profile of the fixed U-OWC integrated with breakwater will be helpful in the design and analysis of efficient hybrid floating breakwater system. © IMechE 2024. 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).

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