Performance assessment of pitch-type wave energy converter in irregular wave conditions on the basis of numerical investigation

Poguluri, Sunny Kumar,Kim, Dongeun,Bae, Yoon Hyeok Techno-Press 2022 Ocean systems engineering Vol.12 No.1

In this paper, a pitch-type wave energy converter (WEC-rotor) is investigated in irregular wave conditions for the real sea testing at the west coast of Jeju Island, South Korea. The present research builds on and extends our previous work on regular waves to irregular waves. The hydrodynamic characteristics of the WEC-rotor are assessed by establishing a quasi-two-dimensional numerical wave tank using computational fluid dynamics by solving the Reynolds-averaged Navier-Stokes equation. The numerical solution is validated with physical experiments, and the comparison shows good agreement. Furthermore, the hydrodynamic performance of the WEC-rotor is explored by investigating the effect of the power take-off (PTO) loading torque by one-way and two-way systems, the wave height, the wave period, operational and high sea wave conditions. Irrespective of the sea wave conditions, the absorbed power is quadratic in nature with the one-way and two-way PTO loading systems. The power absorption increases with the wave height, and the increment is rapid and mild in the two-way and one-way PTO loading torques, respectively. The pitch response amplitude operator increases as the wave period increases until the maximum value and then decreases. For a fixed PTO loading, the power and efficiency are higher in the two-way PTO loading system than in the one-way PTO loading system at different wave periods.

Design optimization of asymmetric wave energy converter using artificial neural network model

Poguluri Sunny Kumar,Kim Dongeun,Lee Yeonbin,신정헌,배윤혁 대한조선학회 2023 International Journal of Naval Architecture and Oc Vol.15 No.-

The present study aims to improve the mean extracted power of a Wave Energy Converter (WEC) by mapping the parameters of its ballast weight and position, wave frequency, viscosity, and Power Take-Off (PTO) damping using an Artificial Neural Network (ANN) model. A total of 25 types of WEC rotors are designed with varying ballast weights and positions. The hydrodynamic coefficient and response of each rotor are determined using linear potential theory and viscous damping is estimated using computational fluid dynamics. The optimal design parameters are obtained by applying the trained model to a large randomly generated input dataset and the prediction output is evaluated to determine the best design parameters. According to the findings of the study, a well-trained model can predict and adopt to the nonlinear behavior of the given dataset as well as provide the optimal design parameters for the selected pitch-type WEC rotor.

Numerical Hydrodynamic Analysis of a Wave Energy Convertor- Rotor in Irregular Waves

Sunny Kumar Poguluri(포구루리 써니 쿠마르),Dongeun Kim(김동은),Yoon Hyeok Bae(배윤혁) 한국신재생에너지학회 2021 한국신재생에너지학회 학술대회논문집 Vol.2021 No.7

In this study, performance assessment of the wave power absorption characteristics of an wave energy converter (WEC) rotor has been investigated using nonlinear – computational fluid dynamics (CFD) in irregular waves. Initially, the experimental results based on regular waves are used to validate the CFD results. Further, it has been extended to irregular waves where the primary focus is to check whether an optimum PTO loading can be achievable for the present WEC-rotor in irregular waves. The success of any WEC largely depends on the power take off (PTO) system which converts the mechanical energy into a more useful energy. For the purpose, the implementation and simulation of the damping mechanism is carried out by the coulomb damping which broadly replicate the PTO characteristics of a typical hydraulic system in irregular waves. The pitch response and rotational moment of the WEC-rotor in regular waves, shows the clockwise pitch motion is higher than the counter-clockwise pitch motion due to its unique asymmetric geometric configuration of the rotor. The major part of the study deals with the one-way PTO system that gives a torque only in one direction and compared with the two-way PTO system for the operational wave conditions.

Experimental and numerical investigation of a surface-fixed horizontal porous wave barrier

Poguluri, Sunny Kumar,Kim, Jeongrok,George, Arun,Cho, I.H. Techno-Press 2021 Ocean systems engineering Vol.11 No.1

Experimental and numerical investigations were conducted to study the performance of a surface-fixed horizontal porous wave barrier in regular waves. The characteristics of the reflection and transmission coefficients, energy dissipation, and vertical wave force were examined versus different porosities of the barrier. Numerical simulations based on 3D Reynolds Averaged Navier-Stokes equations with standard low-Re k-ε turbulent closure and volume of fluid approach were accomplished and compared with the experimental results conducted in a 2D wave tank. Experimental measurements and numerical simulations were shown to be in satisfactory agreement. The qualitative wave behavior propagating over a horizontal porous barrier such as wave run-up, wave breaking, air entrapment, jet flow, and vortex generation was reproduced by CFD computation. Through the discrete harmonic decomposition of the vertical wave force on a wave barrier, the nonlinear characteristics were revealed quantitatively. It was concluded that the surface-fixed horizontal barrier is more effective in dissipating wave energy in the short wave period region and more energy conversion was observed from the first harmonic to higher harmonics with the increase of porosity. The present numerical approach will provide a predictive tool for an accurate and efficient design of the surface-fixed horizontal porous wave barrier.

Performance Analysis of Multiple Wave Energy Converters due to Rotor Spacing

Sunny Kumar Poguluri,Dongeun Kim,Haeng Sik Ko,Yoon Hyeok Bae 한국해양공학회 2021 韓國海洋工學會誌 Vol.35 No.3

A numerical hydrodynamic performance analysis of the pitch-type multibody wave energy converter (WEC) is carried out based on both linear potential flow theory and computational fluid dynamics (CFD) in the unidirectional wave condition. In the present study, Salters duck (rotor) is chosen for the analysis. The basic concept of the WEC rotor, which nods when the pressure-induced motions are in phase, is that it converts the kinetic and potential energies of the wave into rotational mechanical energy with the proper power-take-off system. This energy is converted to useful electric energy. The analysis is carried out using three WEC rotors. A multibody analysis using linear potential flow theory is performed using WAMIT (three-dimensional diffraction/radiation potential analysis program), and a CFD analysis is performed by placing three WEC rotors in a numerical wave tank. In particular, the spacing between the three rotors is set to 0.8, 1, and 1.2 times the rotor width, and the hydrodynamic interaction between adjacent rotors is checked. Finally, it is confirmed that the dynamic performance of the rotors slightly changes, but the difference due to the spacing is not noticeable. In addition, the CFD analysis shows a lateral flow phenomenon that cannot be confirmed by linear potential theory, and it is confirmed that the CFD analysis is necessary for the motion analysis of the rotor.

A study on performance assessment of WEC rotor in the Jeju western waters

Poguluri, Sunny Kumar,Bae, Yoon Hyeok Techno-Press 2018 Ocean systems engineering Vol.8 No.4

The dynamic performance of the wave energy converter (WEC) rotor with different geometric parameters such as depth of submergence and beak angle has been assessed by considering the linear potential flow theory using WAMIT solver and along with the computational fluid dynamics (CFD). The effect of viscous damping is incorporated by conducting numerical free decay test using CFD. The hydrodynamic coefficients obtained from the WAMIT, viscous damping from the CFD and estimated PTO damping are used to solve the equation of motion to obtain the final pitch response, mean optimal power and capture width. The viscous damping is almost 0.9 to 4.6 times when compared to the actual damping. It is observed that by neglecting the viscous damping the pitch response and power are overestimated when compared to the without viscous damping. The performance of the pitch WEC rotor in the Jeju western coast at the Chagwido is analyzed using Joint North Sea Wave Project (JONSWAP) spectrum and square-root of average extracted power is obtained. The performance of WEC rotor with depth of submergence 2.8 m and beak angle $60^{\circ}$ found to be good compared to the other rotors.

Three-Dimensional Computational Aspects of Vertical Axis Wind Turbine Based on Aerodynamic Performance

Sunny Kumar Poguluri,Hyebin Lee,Yoon Hyeok Bae 한국신재생에너지학회 2019 AFORE Vol.2019 No.11

종운동 파력발전장치의 운동 성능 향상을 위한 인공신경망 적용 연구

포구루리 써니 쿠마르(Sunny Kumar Poguluri),김동은(Dongeun Kim),이연빈(Yeonbin Lee),배윤혁(Yoon Hyeok Bae) 한국해양환경·에너지학회 2022 한국해양환경·에너지학회 학술대회논문집 Vol.2022 No.6

다수 배열된 종운동 파력발전장치의 선형 거동에 대한 수치적 연구

김동은,POGULURI SUNNY KUMAR,배윤혁 한국해양환경·에너지학회 2020 한국해양환경·에너지학회지 Vol.23 No.4

Generally, new and renewable energy power generation systems produce electricity by installing and operating multiple modules at the same time to increase power production. This is also included in the case of wave power generation systems using waves. However, when multiple wave energy converters (WECs) are operated at the same time, the behavior is different from that of a single module due to the influence of hydrodynamic interaction between WECs. In this study, to start with the hydrostatic and hydrodynamic coefficients were calculated in the frequency domain using WAMIT (a program based on the linear potential flow theory in three-dimensional diffraction/radiation analyses) which is a commercial code whose pitch motion of a WEC (rotor) is investigated in isolation and then three rotors were analyzed. Once the multi-body motion equation in the frequency domain is calculated, the response amplitude operator (RAO) on period of the incident wave was derived in the linear range. Finally, based on the linear results, the motion performance and power production efficiency of multiple modules were compared with that of isolated module considering the marine environment of the installed sea area. 일반적으로 신·재생에너지 발전 시스템은 전력 생산량 증가를 위해 다수의 모듈을 동시에 설치하여 운용한다. 파랑 에너지를 활용한 파력발전 시스템의 경우도 이에 포함된다. 하지만 다수의 파력발전장치를 동시에 운용할 경우 파력발전장치 상호 간의 유체 동역학적 상호작용의 영향으로 인해 단일 모듈의 경우와는 운동응답이 다소 차이를 보이게 된다. 본 연구에서는 최근 국내에서 기술개발 진행 중인 종운동 로터에 대해서 단일 배치되었을 때를 상용코드인 WAMIT(3차원 회절/방사 포텐셜 해석 프로그램)을 이용하여 주파수영역에서 유체력 계수들을 산출하였고, 이어서 로터가 3개 배열되어 있을 때의 값을 계산하였다. 다음, 주파수 영역에서의 다물체 운동 방정식을 수립한 후 입사파 주기에 따른 RAO(Response amplitude operator)를 선형 범위에서 도출하였다. 최종적으로 선형 결과들을 토대로 설치 해역 해양환경을 고려한 단일 모듈 대비 다수 모듈의 운동 성능과 전력 생산 효율을 비교하였다.

비대칭 형상 파력발전 로터의 선형 거동에 대한 수치적⋅실험적 연구

김동은,Sunny Kumar Poguluri,고행식,이혜빈,배윤혁 한국해양공학회 2019 韓國海洋工學會誌 Vol.33 No.2

Among the various wave power systems, Salter’s duck (rotor) is one of the most effective wave absorbers for extracting wave energy. The rotor shape is designed such that the front part faces the direction of the incident wave, which forces it to bob up and down due to wave-induced water particle motion, whereas the rear part, which is mostly circular in shape, reflects no waves. The asymmetric geometric shape of the duck makes it absorb energy efficiently. In the present study, the rotor was investigated using WAMIT (a program based on the linear potential flow theory in three-dimensional diffraction/radiation analyses) in the frequency domain and verified using OrcaFlex (design and analysis program of marine system) in the time domain. Then, an experimental investigation was conducted to assess the performance of the rotor motion based on the model scale in a two-dimensional (2D) wave tank. Initially, a free decay test (FDT) was carried out to obtain the viscous damping coefficient. The pitch response was extracted from the experimental time series in a periodic regular wave for two different wave heights (1 cm and 3 cm). In addition, the viscous damping coefficient was calculated from the FDT result and fluid forces, obtained from WAMIT, are incorporated into the final response of the rotor. Finally, a comparative study based on experimental and numerical results (WAMIT & OrcaFlex) was performed to confirm the performance reliability of the designed rotor.