Faculty Publications
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Item Coupled dynamic analysis of spar-type floating wind turbine under different wind and wave loading(Springer Science and Business Media Deutschland GmbH, 2021) Rony, J.S.; Karmakar, D.; Guedes Soares, C.G.In the present study, the coupled dynamic modelling of three different configurations of spar platform is performed using time-domain aero-servo-hydro-elastic simulation. The spar platforms are coupled with 5 MW NREL floating wind turbine and mooring sub-models. The coupled aero-servo-hydro-elastic simulation is performed using the simulation tool FAST with WAMIT as the sub module to obtain frequency domain hydrodynamic characteristics. The major emphasis is given to analyse the Response Amplitude Operators (RAOs) to understand the stability of the structures. The responses are calculated for surge, sway, heave, roll, pitch and yaw motions. The study determines the performance of the structure under the wind load developed for the turbine support structure on analysing the tower base forces and moments. The analysis for three different configurations of spar platform is performed for various environmental conditions of North Sea. The studies observed that the responses of the platforms tend to increase with increase in wind speed and wave height. Further, it is observed that surge and pitch motion is dominant for all the three configurations of spar platform. The present study provides an insight into the power performance, structural integrity and dynamic motions of the floating wind turbine under various operational and survival conditions which help the designers to develop better design standards. © 2021, Sociedade Brasileira de Engenharia Naval.Item Coupled Dynamic Analysis of Hybrid Offshore Wind Turbine and Wave Energy Converter(American Society of Mechanical Engineers (ASME), 2022) Rony, J.S.; Karmakar, D.The combined offshore wind and wave energy on an integrated platform is an economical solution for the offshore energy industry as they share the infrastructure and ocean space. The study presents the dynamic analysis of the Submerged Tension-Leg Platform (STLP) combined with a heaving-type point absorber wave energy converter (WEC). The feasibility study of the hybrid concept is performed using the aero-servo-hydro-elastic simulation tool FAST. The study analyzes the responses of the combined system to understand the influence of the WECs on the STLP platform for various operating conditions of the wind turbine under regular and irregular waves. Positive synergy is observed between the platform and the WECs, and the study also focuses on the forces and moments developed at the interface of the tower and platform to understand the effect of wind energy on the turbine tower and the importance of motion amplitudes on the performance of the combined platform system. The mean and standard deviation for the translation and rotational motions of combined wind and wave energy converters are determined for different sea states under both regular and irregular waves to analyze the change in responses of the structure. The study observed a reduction in motion amplitudes of the hybrid floating system with the addition of the wave energy converters around the STLP floater to improve the energy efficiency of the hybrid system. The study helps in understanding the best possible arrangement of point absorber-type wave energy converters at the conceptual stage of the design process. © © 2021 by ASMEItem Numerical investigation of offshore wind turbine combined with wave energy converter(Springer Nature, 2023) Rony, J.S.; Sai, K.C.; Karmakar, D.The coupled dynamic analysis is performed for three different types of offshore floating platforms combined with a wave energy converter (WEC) mounting a 5-MW NREL (National Renewable Energy Laboratory) wind turbine. The Response Amplitude Operators (RAOs) are analysed for the three concepts of combined wind and wave energy platforms for different wind and wave conditions. The hydrodynamic performance for the three different platforms is conducted considering different load cases. The time domain aero-servo-hydro-elastic tool is used to study the motion responses of the combined system under real operational conditions. The platform’s responses are observed to increase with the increase in the wind speed. In the case of floating hybrid platform, surge responses are minimal for the hybrid spar-tours combination for any load case condition. Minimum surge and sway ensure higher wind power absorption. The study further focuses on the tower base forces and moments to study the impact of wind and waves on the combined floater. Fore-aft shear forces and fore-aft bending moments are higher for the platforms indicating the importance of wind-wave loading. The time domain responses are further used as the transfer function to predict the most probable maximum values of motion amplitude expected to occur during the life-time of the structure which can be used for designing a floating wind turbine (FWT) against overturning in high waves. The long-term models are constructed using various short-term situations expected to occur during the structure’s life-time and weighing them appropriately. The long-term distribution uses North Atlantic wave data, and short-term responses are calculated considering Rayleigh distribution. A brief comparative study of the three combined offshore floaters is performed to understand the structural integrity, power performance and dynamic motions of the floating wind energy platform combined with WECs. © 2023, The Author(s), under exclusive licence to Sociedade Brasileira de Engenharia Naval.Item Reliability based design loads of hybrid submerged tension leg-type offshore wind turbine platform(Springer Science and Business Media Deutschland GmbH, 2025) Rony, J.S.; Karmakar, D.The environmental contour (EC) method is one of the popular modelling approaches to predict the long-term responses of the Floating Offshore Wind Turbine (FOWT) platforms. The method is recommended in the design guidelines and standards as, it emerged as a practical method to estimate the extreme dynamic responses for relatively minimal number of environmental conditions. The EC method has the advantage of separating the probabilistic description of the environment from the structural design. In the present study the 1-D and 2-D EC models are estimated based on the Inverse First Order Reliability Method (IFORM). The models estimated were used to predict the extreme long-term responses of the single Submerged Tension Leg Platform (STLP) and the STLP combined with heaving cone-cylinder wave energy converters (STLP-WEC). The aero-servo-hydro-elastic simulation tool FAST is used to simulate the extreme responses for the five particular return periods (1-Year, 10-Year, 20-Year, 50-Year and 100-Year) considering the HornsRev site. The wind load conditions for the FAST platform were simulated using the tool TURBSIM. The study further analysed the long-term extreme moments developed at the base of the turbine tower to analyse the influence of the wind and wave load on the wind power absorption. The maximum value of the mooring line tension developed on the mooring cables of the platform for different return period conditions are also studied to understand the reliability of the floating system. The study observed to be useful for predicting the long-term design loads of STLP wind turbine. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.Item 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.