요트 킬의 형상에 따른 유체력 및 유동 특성 변화 연구

최기철 한국해양대학교 대학원 2006 국내석사

In this research measuring resistance of sailing yacht, side Force and yaw Moment using resistance test, force measuring test at various combinations of heeling and leeway angles & Keel test when Keel attached and wasn't attached on the bottom of hull part. When sailing yacht is upright condition, measuring difference of side force when keel attached and wasn't attached on the bottom of hull part and comparing Keel's side force measured by Keel test. From this result searching correlation between hull and Keel. And case that leeway angle is 10° and heeling angle 20°, measuring flow of wake by PIV(particle Image Velocimetry) method when Keel attached on the bottom of hull part and Keel is alone in order to verify whether ignore of correlation between hull and Keel is possible when there is leeway angle and heel angle as well as sailing yacht is upright condition. From these results gaining conclusion of ignore of correlation between hull and Keel is possible. Therefore researching Hydrodynamic Force and Fluid Flow Characteristics change of 3 types of Keel using PIV(particle Image Velocimetry) method and Keel test. 3 types of Keel were Fin Keel, Bulb Keel, Winglet Keel.

조류발전용 H-다리우스형 수직축 터빈의 유체역학적 성능해석을 위한 실험 및 수치적 연구

최다혜 한국해양대학교 2011 국내석사

This study on the tidal stream power plants related to new and renewable energy is investigated by numerical analyses about the fluid dynamic performance of vertical axis tidal stream turbines(VAT) with computational fluid dynamics(CFD). Based on the extensive research cases about VAT and their trends, it is understood that positive researches on VAT are necessary. This study performs the experimental and numerical analyses mainly on H-Darrieus turbines, which are easy to be produced and designed, among VAT. Numerical analyses analyzed the flow in unsteady flow conditions around two- and three-dimensional VAT using FLUENT. A rotating flow field is implemented for sliding mesh techniques for the rotation of rotor, and a turbulence model is used. The experimental analyses are carried out at the circulating water channel(CWC) of Korea Maritime University. The experimental equipments including the initial driving of turbines are installed in CWC considering the vibration of rotor shart induced by fluctuating load of rotor blade. The result of numerical analyses are compared with the experimental result. In case of the numerical analyses of a H-Darrieus turbine, the patterns of two- & three-dimensional analyses are similar, but there is some difference in the absolute values due to the various three-dimensional effects. In case of the numerical analyses, additional studies are needed as there is some difference based on the boundary conditions. The maximum efficiency of experimental results is approximately 36%, but it included a lot of uncertainty error. So additional studies are needed to explain the blockage effect of CWC. It is understood that based on the study results about VAT, the studies on various shapes of turbines like Davis turbine and Helical turbine are considered to be possible gradually.

30kW급 방파제 연계형 파력발전용 임펄스터빈 성능의 수치적 연구

양승권 한국해양대학교 대학원 2018 국내석사

This paper is about the performance analysis according to turbine design variables to improve the performance of the impulse turbine for 30kW wave-power generation. We say that the findings were obtained through further research based on the performance study of the turbine through the participation of the breakwater-linked wave power generation fusion and convergence technology development project organized by the Ministry of Maritime Affairs and Fisheries which has been carried out since 2016. For the numerical analysis, FLUENT, a general purpose code of the fluid analysis, was used. In order to perform the impulse turbine performance analysis, the verification was performed for a pair of guide vanes and turbine blades. We carried out the verification by applying the Moving Reference Frame method which gives relative velocity to the rotating region without rotating the turbine. Based on the verification results, the performance analysis of 30kW impulse turbine was conducted. For the verification of the impulse turbine, the turbine of Setoguchi et al., (2001) was compared and numerical calculation was carried out by changing the blade rotation speed with the axial flow velocity fixed. The three - dimensional numerical calculation was used to compare the input coefficient and torque coefficient efficiency values of the turbine at 0.5 ~ 2.5 of flow coefficients and the numerical analysis result showed that they well match with the experimental values qualitatively and quantitatively. For the impulse turbine for 30kw wave generation, the turbine performance was examined with respect to the number of main design variable wings (), guide vane angle (), distance between guide vane and wing (), wing tip clearance () and hub ratio. The performance analysis was performed for a ring type, an end-plate type, a back tilt angle, a ring and a back tilt angle simultaneous application type turbine which deform the shape of turbine blades. The impulse turbine design variable study showed that the turbine performance is the best when the number of turbine blades is 30, the guide vane angle is 35˚, the distance between the guide vane and the wing () is 0.35 and the smaller the blade tip clearance () and when hub ratio is 0.7. The back tilt angle was applied to the front and rear of the turbine blade. The result of the analysis of the turbine applying a total of back tilt angles showed that the efficiency of the turbine applying () -5˚at the front and () +6˚ at the rear was improved by approximately 8%. For a ring-type turbine applying a ring-shaped band at the end of the turbine blade, the turbine performance was improved as the ring-shaped mouth axial direction length () increases. It was found that as the ring thickness () increases, the input and output torque values of the turbine gradually increase and the efficiency value gradually increases and decreases again based on when tp* is 10. It was also found that the efficiency of three types of impulse turbines applying End-plate type, ring and back tilt angle simultaneous application type, ring type was more improved than that of general type turbine by 5, 9, 10%, respectively. Based on the study on design variables of impulse turbine using the numerical analysis, a total of three turbines (general type, back tilt angle type, and ring type) were derived. It was found that the turbine performance is good in the order of ring type, sweep angle type, and general type turbines. In addition, a model turbine with 0.38 m of diameter for the model test was designed. Model turbine performance data performed by the Korea Research Institute of Ships & Ocean Engineering using Wave simulator equipment were compared through the numerical analysis. Finally, the ring type impulse turbine with best performance of 0.8m in diameter was designed. The maximum efficiency of the impulse turbine was found to be about 50%. Also, the turbine performance chart depending on each flow (1, 3, 6, 9 ) was derived for the final designed turbine. 본 논문은 30kW급 파력발전용 임펄스터빈의 성능향상을 목적으로 터빈 설계변수에 따른 성능해석 연구에 대한 내용을 다루고 있다. 2016년부터 진행 중인 해양수산부 주관의 방파제 연계형 파력발전 융복합 기술개발 사업에 참여하여, 터빈의 성능연구 내용을 바탕으로 추가 연구를 통해 얻은 결과임을 밝힌다. 수치해석은 유체해석 범용코드인 FLUENT를 이용하였다. 임펄스터빈 성능해석을 수행하기 위해 한 쌍의 가이드베인과 터빈날개를 대상으로 검증을 수행하였다. 터빈을 회전시키지 않고 회전영역에 상대속도를 부여하는 Moving Reference Frame기법을 적용하여 검증을 수행하였다. 검증결과를 바탕으로 30kW급 임펄스터빈의 성능해석을 수행하였다. 임펄스터빈 검증은 Setoguchi et al., (2001)의 터빈을 비교하였고, 축방향 유속을 고정한 상태에서 날개회전속도를 변경하는 방법으로 수치계산을 진행하였다. 3차원 수치계산으로 유동계수 0.5~2.5의 구간에서 터빈의 입력계수, 토크계수 효율값을 비교하였으며, 수치해석결과 실험값과 정성적, 정량적으로 잘 일치함을 확인하였다. 30kw급 파력발전용 임펄스터빈을 대상으로 주요 설계변수 날개수(), 가이드베인 각도(), 가이드베인과 날개사이 거리(), 날개끝간격(), 허브비에 대하여 터빈성능을 알아보았다. 터빈날개의 형상을 변형시키는 링타입형, End-plate타입형, 뒤젖힘각형, 링 및 뒤젖힘각 동시적용형 터빈에 대해 성능해석을 수행하였다. 임펄스터빈 설계변수 연구를 통해 터빈 날개수가 30개일 때, 가이드베인각도 35도일 때, 가이드베인과 날개사이 거리()이 0.35일 때, 날개끝간극()가 작아질수록, 허브비가 0.7일 때 터빈성능이 가장 좋음을 확인하였다. 터빈날개 전단과 후단에 뒤젖힘각을 적용하였다. 총 20가지의 뒤젖힘각을 적용한 터빈을 분석한 결과 전단에() -5˚, 후단에() +6˚를 적용한 터빈이 약8%의 효율이 향상됨을 확인하였다. 터빈 날개 끝에 링형상의 띠를 적용한 링타입터빈의 경우 링형상의 입구축방향 길이()가 커짐에 따라 터빈성능이 향상되었다. 링의 두께()가 증가함에 따라 터빈의 입력계수값과 토크계수값은 점차 커지며 효율값은 점차 증가 하다가 가 10일 때를 기준으로 다시 감소함을 확인 하였다. End-plate형, 링 및 뒤젖힘각 동시적용형, 링타입형을 적용한 3가지 종류의 임펄스터빈이 일반형터빈보다 각각 5, 9, 10% 효율이 향상됨을 확인하였다. 수치해석을 이용한 임펄스터빈 설계변수 연구를 바탕으로 최적의 성능을 가지는 링타입형 임펄스터빈을 도출하였다. 모형시험을 위한 직경 0.38m 모형터빈을 설계하였다. 선박해양플랜트연구소에서 Wave simulator장비를 이용하여 수행한 모형터빈 성능자료를 수치해석을 통해 비교하였다. 임펄스터빈의 최대효율은 약 50%임을 확인하였다. 또한, 최종 설계된 터빈을 대상으로 각각의 유량(1, 3, 6, 9 )에 따른 터빈성능 도표를 도출하였다.

수치해석을 이용한 파력발전용 임펄스 터어빈 주위 유동 해석 및 성능 연구

문재승 한국해양대학교 대학원 2006 국내석사

Of several types of variable air turbines for wave energy conversion investigated, a Wells turbine has been widely applied for wave energy conversion mainly due to its simple structured at 1990s. However the Wells Turbine has some inherent shortcomings; short operating range, not good self starting characteristics, higher axial thrust and noise. The impulse turbine has newly been proposed to overcome these drawbacks and have clarified that the turbine can be operated with higher turbine efficiency and lower rotational speed than those wells turbine. This Paper deals with the performance analysis and design of impulse turbine for OWC-type wave energy plant. Numerical analysis is performed using a commercial software FLUENT. First, this parametric study included variation of several important parameters such as the number and shape of blades, hub ratio, tip clearance and setting angle of guide vane. Second, this paper has proposed special-type turbine more efficient so-called "Ring-type Turbine". The main idea of the proposed turbine rotor was to minimize the adverse effect of tip clearance of turbine blade. Results show that the efficiency increases up to 10% depending on flow coefficient. Third, the present paper deal with the numerical study to analyze the self-starting performance in a reciprocating air flow generated by sinusoidal motion of wave inside oscillating water column(OWC). Results was compared to that of wells turbine, wells-known wave energy conversion device, and showed that the impulse turbine has a superior self-starting ability. This paper deal with compare the performance of different turbine at scale-up level and under varying input conditions for analysis performance of prototype turbine.

수직축 조류 발전 터빈의 성능 해석 및 설계

한준선 한국해양대학교 대학원 2010 국내석사

This thesis deals with the design and performance analysis of vertical-axis tidal current turbine (VAT). VAT is well-known as its superior starting and operational abilities regardless of flow direction, while HAT shows the better turbine efficiency than most of VAT. After an extensive literature survey on tidal current power generation, the status and prospects of tidal current energy were summarized to briefly figure out the research direction. Hydrodynamic characteristics of both VAT and HAT (horizontal-type turbine) were also investigated. For the analysis of VAT, the numerical approach was made by using the commercial CFD software FLUENT. GAMBIT was used for the grid generation of 2-D as well as 3-D models. Some typical calculated results were compared to available experimental data to validate the current numerical result. Although 3-D flow analysis was also made and introduced to investigate the flow characteristics in overall, most of calculated results were obtained using 2-D analysis due to its relative simplicity and relevance in massive calculations especially for the parametric study by varying several parameters to improve the turbine performance. In the present study, parameters such as number of blade, blade chord, solidity, pitch and blade chamber were varied for the wide range of TSR (tip speed ratio) to find out the best possible combinations providing the best hydrodynamic performance. The finally obtained VAT needs to be validated by further experimental investigation.

수직축 조류발전 터빈의 성능에 미치는 설계인자들의 영향 연구

이대형 한국해양대학교 대학원 2012 국내석사

The west and south coastal region of Korea has very strong tidal current speeds and therefore accommodates many suitable sites for the application of Tidal Current Power. This paper deals with effect that design parameter of tidal current vertical axis turbine to performance. For the analysis on VATT(Vertical-Axis Tidal current Turbine), the numerical approach was made by using the commercial CFD software FLUENT 6.3. First at all, they ascertained that characteristic of turbine parameters such as span, turbine diameter, number of blade, shape of blade, tip speed ratio, solidity and current speed. Second, this paper provided that effect of turbine diameter and current speed on the efficiency of VATT. And than, study on the effect of Reynolds number in turbine efficiency quite big especially at low Reynolds number below. Third, the paper deal with any blockages such as duct or flow fence around the turbine. turbine performance has benefit by a blockage effect. Fourth, present paper has proposed optimal solidity for VATT.

수치해석을 이용한 OWC형 파력발전시스템의 통합성능해석

Jin Ji Yuan 한국해양대학교 대학원 2013 국내박사

Plenty of wave energy absorption devices have been invented, and several of them have been utilized in the electricity generation. The Oscillating Water Column (OWC) type has been widely employed in the application for the wave energy conversion for last 30 years. Due to the advantages of rather reliable converting technique and comparable production cost over other types of ocean energy, wave energy conversion system is considered to be feasible for the establishment of commercial power production. The present paper deals with the numerical study on integrated OWC system for wave energy conversion. All the numerical study was based on Reynolds averaged Navier-Stokes(RANS) equations. An OWC wave energy converting system includes three energy converting stages: 1) The OWC inside a chamber forces air alternately into and out of the atmosphere through the duct. 2) A turbine with symmetric blades transforms the bi-directional air flow energy into a mechanical torque. 3) An electric generator linked to the turbine transforms the torque into electrical power. Since the hydro- and aero-dynamic performance analyses are of primary concern for the thesis, the third stage for electric generator is not considered in this study. For the study of first energy converting stage, the numerical wave tank is established. The VOF model are adopted to calculate the wave generation and propagation in the numerical wave tank. The two-dimensional & three dimensional numerical wave tanks are validated with the analytic results and the predicted performance of oscillating water column is compared with the available experimental data. Various parameters of chamber geometry are investigated to demonstrate the effects of shape parameters on the wave field, water column oscillation in the chamber and wave energy conversion. For the study of second energy converting stage, the numerical model for rotating machine is developed based on MRF technique. To optimize the impulse turbine, the effects of several shape parameters on operating performance are investigated such as number of blade, angle of guide vane, tip clearance, hub ratio, G/lr, sweep angle & staggered blade. Through the parametric study, the optimized impulse turbine is drawn out in diameter D=1.8m for 250kW capability. The fully transient calculation model is developed to investigate the unsteady characteristics of impulse turbine, especially self-starting performance under various incident air flow conditions. For the study of integrated system of chamber and turbine, the orifice module is adopted. The experiments on relationship between the air flow velocity and the pressure difference between two side of the turbine and orifice are carried out. The corresponding simulation is performed to validate the capability of the numerical model on the prediction of pressure drop. The numerical wave tank is embedded with the orifice module to investigate the integrated OWC system and interaction of turbine effects. The effects of wave directions on the performance of an OWC chamber have been investigated. Two test conditions which are with and without turbine effects was carried out in experimental study. The experiment was carried out in a 3-D wave basin. The wave elevation inside the chamber was measured at center point under various incident wave conditions and wave directions from 0o to 90o. A CFD study using a numerical wave tank was also conducted to compare the results with the experimental data and to reveal the detailed flows around the chamber. In order to evaluate the operating performance of OWC facilities in real sea conditions, this paper proposed the integrated numerical techniques for OWC - turbine system to induce the influences of the other processing. The real sea conditions are considered as the combination of regular waves to estimate hydropower from incident waves. The estimating method for individual regular waves is based on the numerical simulation of the OWC chamber with effects of turbine effects. The evaluation of the integrated OWC system by using look-up table to estimate the averaged power output of Jeju OWC plant is also presented. The look-up table contains three kinds of database: the orifice, OWC - orifice and turbine performance databases. The orifice database shows the relationship between the air flow rate and pressure drop for different orifice diameters. The OWC - orifice database shows the relationship between the incident wave condition and air flow rate generated inside the OWC chamber with various orifice devices. The turbine performance database presents the steady-state performance of the designed impulse turbine under various air flow rates and rotational speeds. The real-time power output of the OWC system can be predicted with the look-up table by iterations of each stage. Finally the process of predicting the operating performance in the real sea conditions using look-up table is presented. The software with Graphic User’s Interface (GUI) contains all look-up table is developed using Visual C++ language, which can complete the iteration process automatically.

초기트림을 고려한 선박의 저항성능 연구

이정기 한국해양대학교 대학원 2012 국내석사

The attitude of hull is changed by trim depend on pressure difference between bow and stern on cruising speed and various conditions. As ships proceed in confined water, squat phenomenon is occurred by pressure drop of bottom and difference of density. In addition, trim condition can be changed by cruising condition and the status of cargo loaded. In recent years, the shipowner requested resistance performance of hull on various condition to heavy industry. As such these case, change in attitude of the hull affect the resistance performance and it is important to predict. In this paper, as the basic study for change in attitude, numerical calculations were carried out to predict components of initial trim resistance using FLUENT. Based on the concept of resistance components, the grand total resistance can be obtained by adding initial trim resistance component to total resistance component on calm water. In order to validate the numerical calculations, DTMB5415 and KRISO Container Ship model was chosen and numerical calculation was performed on fixed condition. The results were compared with the results of the CFD Workshop2005 and MOERI experiment data. Initial trim for KRISO Container Ship to draft bow and stern by constant was applied by varying and typical hull type of power yacht obtained through surveys was applied in the same way. Numerical calculations were performed for this condition due to the initial trim coefficient of residuary resistance changes investigated. The residuary resistance on initial trim condition is decrease due to increase the amount of stern trim. By considering the initial trim, this study is expected to contribute initial design and optimization of hull.

위상 평균법을 이용한 진동 날개 주위 유동의 실험적 해석

김무롱 한국해양대학교 대학원 2006 국내석사

First, the present study deals with the visualization of flow fields around and behind a 2-D & 3-D NACA0012 airfoil oscillating with various frequencies. Since the unsteadiness of flow is then known to be depending on the reduced frequency K, the airfoil was oscillated by using a servo-motor which could be computer-controlled at wide range of frequencies and amplitudes. It was tentatively found that the gloval flow field was greatly altered by the reduced frequency and the mean angle of attack by the frequency. Results contained in this paper could provide the valuable information on the study for fluid-structure interaction. And then, sn experimental study was carried out to examine quantitatively the vortical flow fields around and behind an oscillating 2-dimensional airfoil by phase. A NACA0012 airfoil with an aspect ratio of 4.0 was mounted on the middle section of the CWC (Circulating Water Channel), and the airfoil was sinusoidally pitched about the quarter chord. The mean angle of attack was set at various angles and the amplitude of oscillation was set at 2.5. The flow visualization and measurements were made for depending on the reduced frequency K, and Reynolds number Rn. This paper introduces the results by an experiments and measures, and that compares case the ignore phase and case that is not so. Last, Evolution of the unsteady three-dimensional tip vortex in the wake field of a rectangular NACA 0012 hydrofoil in pitching motion is investigated. Measurements were made in CWC using PIV. An airfoil has an aspect ratio of 5 with chord length of 10cm. Pitching angle and mean angle of attack were set to 5° and 10°, respectively. (i.e. the angle of attack varies from 5° to 15°. Frequency of oscillation was varied from 0.1Hz to 1Hz in order to study the effect of unsteadiness imposed by various frequencies, which correspond to the reduced frequency of K=0.1, 0.21, 0.52 and 1.06. Reynolds number based on chord length and free-stream velocity was 3.0×104. Phase-averaging technique was employed. Unsteadiness and variation of the size and characteristics of tip vortex at different reduced frequency were discussed.

수치해석을 이용한 OWC형 파력발전시스템의 통합성능해석

김길원 한국해양대학교 대학원 2013 국내박사