Faculty Publications
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Item Implementation of Turbine Emulator(Universitatea Politehnica din Timisoara blucretiu@yahoo.com, 2011) Vinatha Urundady, U.; Vittal, K.P.A Wave Turbine Emulator (WTE) is designed and implemented considering the realistic site data based on Oscillating Water Column (OWC) principle. Wave Turbine Emulator (WTE) is the important equipment for developing the Wave Energy Conversion systems. The Emulator reflects the actual behavior of the wave turbine without reliance on natural wave resources and actual wave turbine. It offers a controllable test environment that allows the evaluation and improvement of control schemes for electric generators which is hard to achieve with an actual wave turbine. The WTE can accurately reproduce the characteristics of real wave turbine. The Emulator can be used for research applications to drive an electrical generator in a similar way as a practical wave turbine. A prototype of turbine emulator is built in the laboratory using a three phase synchronous motor controlled by Rexroth Indra Drive. The system comprises of Simulink model of the Turbine, model of the oscillating water column, Data Acquisition card Instruments, Digital to Analog Converter, 3-phase Permanent magnet Synchronous motor driven by Rexroth Indra Drive Controller.Item Development of wave turbine emulator in a laboratory environment(2013) Vinatha Urundady, U.; Vittal, K.P.Wave turbine emulator (WTE) is an important equipment for developing wave energy conversion system. The emulator reflects the actual behavior of the wave turbine by reproducing the characteristics of real wave turbine without reliance on natural wave resources and actual wave turbine. It offers a controllable test environment that allows the evaluation and improvement of control schemes for electric generators. The emulator can be used for research applications to drive an electrical generator in a similar way as a practical wave turbine. This article presents the development of a WTE in a laboratory environment and studies on the behavior of electrical generator coupled to the emulator. The structure of a WTE consists of a PC where the characteristics of the turbine are implemented, ac drive to emulate the turbine rotor, feedback mechanism from the drive and power electronic equipment to control the drive. The feedback signal is acquired by the PC through an A/D converter, and the signal for driving the power electronic device comes from the PC through a D/A converter.Item Power control strategy for grid connected permanent magnet synchronous generator of a distributed generation unit(Inderscience Enterprises Ltd., 2014) Vinatha Urundady, V.; Vittal, P.K.This paper describes the studies on the operation and control of a variable speed wave energy conversion system. The wave energy conversion system considered is oscillating-water-column (OWC) based Wells turbine driven permanent magnet synchronous generator connected to the grid by means of fully controlled frequency converter. In such systems primary aim is to achieve a low distortion, high power quality power export from the converter with the objective to regulate the power flow or power factor optimisation. In this paper wave energy conversion system is modelled and control schemes are implemented for regulating the dc link voltage for varying input conditions and for regulating the grid current entering the distribution network and hence the power flow into the grid. Response of the system is investigated under steady state, dynamic and transient conditions. In each case the grid current distortion and the dynamic performance of the converter control schemes are evaluated. © © 2014 Inderscience Enterprises Ltd.Item Hydrodynamic performance of pile restrained U-shaped OWC device using boundary element method(Elsevier Ltd, 2024) Muduli, R.; Patil, S.B.; Karmakar, D.The hydrodynamic performance of a pile-restrained U-shaped Oscillating Water Column (U-OWC) device under the action of normal incident waves is analysed using the Boundary Element Method (BEM). The hydrodynamic parameters, such as the radiation susceptance and conductance coefficients and hydrodynamic efficiency, are analysed for various cases of different structural parameters of U-OWC. It is observed that the theoretical maximum efficiency can be achieved for a wide range of wavenumbers by appropriate tweaking and optimisation of the device geometry. The resonance enables the device to reach the maximum possible efficiency and the phenomenon of obtaining the maximum efficiency of the final optimised geometry is achieved. The shorter length of draft of the device is chosen over longer draft considering the high construction cost as well as efficiency enhancement of the device, even though the longer draft is observed to perform marginally better in a narrow wave number range. The numerical investigation of the theoretical maximum efficiency is observed to be 100% whenever the μ (dimensionless radiation susceptance coefficient) crosses the zero mark. Consequently, the maximum theoretical efficiency is observed close to maximum whenever μ is close to zero. The final optimised geometry consisting of an inward inclined top wall configuration performs best but could be challenging in actual construction. Further, on inclining the bottom wall in the inwards or outward direction does not result in better performance than inclining only the top wall. The present study explores a novel concept of pile-restrained U-OWC kept near the surface and will be helpful in determining the best-performing geometry for the device. © 2023 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 Hydrodynamic performance of an oscillating water column WEC integrated with a pile-restrained H-type breakwater(Taylor and Francis Ltd., 2025) Vishwakarma, R.D.; Muduli, R.; Karmakar, D.The present study examines the hydrodynamic performance of an oscillating water column (OWC) wave energy converter (WEC) integrated into a pile restrained H-type breakwater. A three-dimensional model study is performed using ANSYS-AQWA based on potential flow theory. The results for the incident wave excitation force, shear force, and bending moment on the pile restrained breakwater and the transmission coefficient are obtained for the regular waves. The effect of incident wave angle on the forces is assessed along with the impact of changes in relative draft and width of the device. The power capture efficiency as well as wave transformation characteristics of the device are evaluated using Boundary Element Method (BEM). The study performed will be helpful to scientists and researchers to design and develop an integrated hybrid breakwater system that can protect the coast and provide useful energy by minimising the impact on the marine ecological system and environment. © 2025 Informa UK Limited, trading as Taylor & Francis Group.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 Hydrodynamic performance of hybrid floating breakwater integrated with oscillating water column(SAGE Publications Ltd, 2025) Vishwakarma, R.D.; Karmakar, D.The present study investigates the hydrodynamic performance of different types of hybrid floating breakwaters (HFB) integrated with an oscillating water column (OWC). The study is performed for five different cross-sectional shapes of HFB, such as rectangular, box, H, ?, and trapezoidal, with the inclusion of OWC of the same dimension in all of the hybrid floating breakwaters. The performance of the HFBs is examined for its motion response, wave transmission coefficient, and power capture under the action of the regular waves, considering the incident wave normal to the structure. The motion response and wave transmission characteristics assessment are based on potential flow theory, and the power capture due to the HFB is assessed using the volume of fluid (VOF) flow computation method. The HFB model performing better in terms of transmission coefficient and power capture considering wider bandwidth for the considered surface gravity wave frequencies is selected to investigate the effect of changes in HFB’s parameters, such as length, width, draft, and wave incident angle on the hydrodynamic performance. Additionally, the streamline contours for the air flow velocity variation through the OWC chamber in different types of hybrid floating structures are analysed for better understanding of flow through visualisation. The aforementioned streamline contour is determined for the wave frequency where the maximum wave energy capture in the HFB models is observed. The study will facilitate the researchers to comprehensively investigate the stability of hybrid floating breakwater under the influence of regular waves with the help of the findings of the present investigation. © IMechE 2025Item 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 analysis of arrays of integrated U-shaped OWC device and ?-breakwater(Elsevier Ltd, 2025) Muduli, R.; Karmakar, D.The hydrodynamic performance of arrays of hybrid floating breakwater consisting of pile-restrained U-shaped Oscillating Water Column (U-OWC) integrated with ?-breakwater is analysed using Boundary Element Method (BEM). The study is performed to analyse the theoretical maximum efficiency, reflection and transmission coefficients and horizontal wave force coefficient on the top wall of the U-OWC integrated with breakwater as a function of the incidence angle as well as the non-dimensional spacing between the devices. The geometrical variations of the U-OWC relative chamber width and draft are considered to study the effect on the hydrodynamic performance. The study reveals that on increasing the relative draft of the U-OWC, the energy conversion efficiency is improved whereas the increase in the relative chamber width beyond 0.5 times the water depth (A2/h=0.5) was detrimental to the efficiency. Further, the wave reflection coefficient as a function of incidence angle is noted to be unaffected by geometric variations of the U-OWC. The wave force coefficients as a function of the non-dimensional spacing is observed to exhibit a sinusoidal pattern for the wave interaction with array of integrated U-OWC with breakwater. The numerical investigation on the array of integrated devices will enhance the knowledge and determine the performance of the array of integrated device. © 2025 Elsevier Ltd