Faculty Publications
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Item 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 Ltd