Faculty Publications
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Item Hydrodynamic analysis of an H-shaped pile-restrained floating breakwater combined with a pair of vertical barriers(Elsevier Ltd, 2024) Panda, A.; Karmakar, D.; Rao, M.The present study analyses the performance of a composite breakwater consisting of an H-shaped breakwater attached with vertical/inclined barriers held from both sides using the Multi-Domain Boundary Element Method (MDBEM). The study is performed to analyse the wave transformation characteristics (reflection and transmission), wave energy dissipation and horizontal wave forces due to the gravity wave-structure interaction. The hydrodynamic performance of the integrated breakwater is performed due to the effect of changing various structural properties such as porosity, width and depth of structural elements, relative spacing between breakwater and barrier, angle of incidence and the inclination of the barriers. The boundary conditions and the corresponding edge conditions are incorporated for each surface and interface and correlated with Green's function to solve the boundary value problem. The detailed study proposes the suitable dimensions of the structural elements of the breakwater for optimal performance. The application of inclined barriers over the vertical barrier in certain conditions for maximising wave reflection is presented and analysed to understand the effectiveness of the barrier inclination. The favourable barrier dimensions and the suitable relative spacing for deep water regions are discussed, and the effect of rigidity and porosity of the barriers are analysed to maximise breakwater performance in wave attenuation. On considering the suitable design parameters and structural stability, the composition of vertical/inclined barriers with an H-shaped pile-restrained floating breakwater serves as a protective component by encountering maximum wave force and dissipating considerable wave energy to provide an efficient solution in harbour protection. © 2024 Elsevier LtdItem Coupled dynamic analysis of semi-submersible floating wind turbine integrated with oscillating water column WEC(Springer Science and Business Media Deutschland GmbH, 2024) Sebastian, B.; Karmakar, D.; Rao, M.The present study envisages to investigate the coupled dynamic behaviour of three configurations of a hybrid wind-wave energy system integrating Oscillating Water Column (OWC) wave energy converters to DeepCwind semi-submersible supporting an NREL (National Renewable Energy Laboratory) 5 MW wind turbine. DeepCwind semi-submersible is a platform designed specifically for the purpose of supporting floating offshore wind turbines and the stability of the platform has been well confirmed by scaled-down experiments and numerical studies. The numerical simulation for the present study is performed using the aero-hydro-servo-elastic tool OpenFAST. The dynamic responses of the hybrid platforms are determined for different operational and parked wind speed conditions of the wind turbine in irregular waves. The motion responses, tower base forces and moments, mooring tensions and power absorption of the hybrid configurations have been characterized. Furthermore, the effect of coupling between the semi-submersible platform and the OWCs is studied by comparing the results of the combined platforms with that of the uncoupled wind energy platform. The coupled dynamic analysis in the time domain shows that increasing the number of OWC helps to reduce the motion responses in heave and pitch. The capture width ratio of the system is observed to be highest for hybrid configuration with a single OWC device. The present study will be helpful in the design and analysis of hybrid floating wave-wind energy platform. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.Item Dynamic analysis of a semi-submersible offshore floating wind turbine combined with wave energy converters(Taylor and Francis Ltd., 2025) Sebastian, B.; Karmakar, D.; Rao, M.Hybrid wind–wave energy systems harness both offshore wind and wave energy resources using a shared floating platform, reducing capital and operational costs through common infrastructure. The present study numerically investigates the dynamic performance and power absorption of three hybrid concepts combining the DeepCwind Semi-submersible Platform (SSP) with (i) Oscillating Water Columns (OWC), (ii) Torus Wave Energy Converter (WEC), and (iii) Flap-type WEC. Frequency-domain analyses using WAMIT and time-domain simulations using OpenFAST are performed to assess platform motions, tower base moments, mooring tensions, and WEC power output for different sea states. The integration of WECs significantly improves the hydrodynamic behaviour of the DeepCwind SSP. Flap-type WECs demonstrate the best dynamic performance, reducing heave and pitch by up to 68% and 58%, and mooring tension by 54%. The OWC system achieves the highest power absorption and a 55% capture width ratio, but increases surge and pitch motions by 6% and 27%, respectively, on introducing additional loads on the system. © 2025 Informa UK Limited, trading as Taylor & Francis Group.Item Experimental investigation on L-Oscillating Water Column wave energy converter integrated with floating cylindrical breakwater(Elsevier Ltd, 2025) Harikrishnan, T.A.; Rao, M.; Rao, S.One promising renewable energy source for the future is wave energy, harnessed through L-Oscillating Water Column (L-OWC) Wave Energy Converters (WECs). Combining this device with lightweight floating breakwaters can have several advantages, including absorbing wave energy and attenuating waves. L-OWC and two cylindrical floating breakwaters, one in front of the structure and one at the back are coupled in the current study. Previous research indicates that the L-shaped OWC configuration is highly effective due to its increased added mass and enhanced structural stability. The 1:30 scale model, combining a floating breakwater with an Oscillating Water Column (OWC) system, was experimentally investigated in the wave flume at the NITK, Department of Water Resources and Ocean Engineering. This setup included L-shaped OWCs integrated with cylindrical breakwater configurations (2C, 3C, and 4C). OWCs integrate with lightweight floating breakwaters, offering both wave attenuation and energy extraction. The OWC achieved maximum efficiency of 30% under optimal conditions, with a wave period of approximately 1.8s and a wave height of 0.06 m for the model with three floating breakwaters. The work aligns with the United Nations' Sustainable Development Goals (SDG), specifically addressing clean and affordable energy (SDG 7), industry, innovation, and infrastructure (SDG 9), life below water (SDG 14), and life on land (SDG 15), highlighting its significant impact. © 2024 Elsevier LtdItem Hydrodynamic performance of floating kelp farms: Wave attenuation and coastal protection potential(Elsevier Ltd, 2025) Surakshitha; Rao, M.; Rao, S.Ecologically rich coastal zone play a crucial role in supporting both biodiversity and the economy. “Soft solutions” for coastal protection, such as vegetated breakwaters and artificial reefs, harness natural features to mitigate coastal erosion. Among these, flexible floating vegetation, such as kelp farms, presents a unique mechanism by altering flow patterns differently than bed-fixed vegetation. This study experimentally investigates the effectiveness of floating kelp farms in dissipating wave energy under monochromatic regular waves. The wave heights ranging from 0.06 m to 0.18 m and periods of 1.6 s–2.8 s is considered. The study examines the effects of two non-dimensional parameters: relative farm width (w/L, 0.1 to 2.5) and relative blade length (l/d, 0.25–1.0), representing the ratios of farm width to wavelength and blade length to water depth, respectively. Under the test conditions investigated, the highest wave dissipation coefficient (Kd ? 0.8) is observed for relative blade lengths of 0.75 and 0.5 at a water depth of 0.45 m. The optimal farm configuration occurred at a relative farm width between 0.3 and 0.4. These findings contribute to a better understanding of the role of kelp farm in wave energy dissipation and highlight its potential as a sustainable alternative for coastal protection. © 2025 Elsevier Ltd