• Title/Summary/Keyword: Running Resistance

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A Study on the Ship Resistance and Moment Prediction for Running Attitude of 30 Feet Catamaran Sailing Yacht (30ft급 쌍동형 세일링 요트의 항주자세에 따른 실선저항 및 모멘트 추정에 대한 연구)

  • Park, Chung-Hwan;Jang, Ho-Yun;Jeong, Jin-Wook;Lee, Byung-Sung;Chun, Ho-Hwan
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.3
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    • pp.321-327
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    • 2010
  • During sailing by wind-driven thrust on the sail, a catamaran sailing yacht generates leeway and heeling. For estimating resistance and moment prediction of a real ship by changing of running attitude, a model test of the ship has to be carried out. This study aims at establishing experimental techniques for a catamaran sailing yacht by changed attitude during running direction. Through the model test, drag and side force of the real ship are predicted. Also through experiment, rolling and yawing moments were considered.

A Study on the Scale Effect and Improvement of Resistance Performance Based on Running Attitude Control of Small High-Speed Vessel (소형 고속선박의 항주자세 제어에 따른 저항성능 개선 및 축척 효과에 관한 연구)

  • Lee, Jonghyeon;Park, Dong-Woo
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.27 no.4
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    • pp.538-549
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    • 2021
  • In this study, a trim tab on the stern hull of a small high-speed vessel of approximately 10 m length sailing at a Froude number of 1.0 was designed for energy efficiency. The running attitude and resistance performance of the bare hull and trim tab hull at several angles to the base line were analyzed for model and full scale ships using computational fluid dynamics, and compared to investigate the scale effect. The analysis results for the bare hull were quite similar, but a difference in the attitude control under same conditions of the trim tab was observed, resulting in the total resistance error. However, there was no significant difference in tendency of the variation in the resistance with the attitude. Thus, the optimum running attitude could be determined from the tendency despite the scale effect, but a full scale analysis is required to analyze the control of the attitude by the trim tab and flow characteristics near the full scale ship.

A Study on the Resistance Performance and Flow Pattern of High Speed Planing Hull using CFD (전산유체계산을 통한 고속 활주선의 저항성능 및 유동분포 해석)

  • Park, Kyurin;Kim, Dong Jin;Kim, Sun Young;Rhee, Shin Hyung
    • Journal of the Society of Naval Architects of Korea
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    • v.56 no.1
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    • pp.23-33
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    • 2019
  • Unmanned Surface Vehicle (USV) is being developed to do maritime survey and maritime surveillance at Korea Research Institute of Ships & Ocean engineering (KRISO). The goal is that USV should be operated at the maximum speed of 45 knots and it should be operated at sea state 4. Therefore the planing hull of USV should be excellent in resistance performance and manoeuvring performance. It is needed to check its performance using Experimental Fluid Dynamics (EFD), Computational Fluid Dynamics (CFD) or analytic method before designing the hull. In this study, resistance performance was analyzed by EFD and CFD. EFD with heave and pitch was performed at high speed towing system in Seoul National University. CFD was performed using SNUFOAM based on openFOAM with dynamic mesh to calculate running attitudes. The results of CFD were compared with EFD results. The results of CFD were resistance, running attitudes and wave height. The flow distribution and pressure distribution were also analyzed. The results of numerical resistance was under estimated than EFD. Even though the results of CFD have a slight limitation, it can be successfully used to estimate the resistance performance of planing hull. In addition it can be used as a supplement for EFD results.

Analysis of pneumatic braking component effects and characteristics of a diesel electric locomotive (디젤전기기관차의 공압제동 영향인자 및 특성 분석)

  • Choi, Don Bum;Kim, Min-Soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.11
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    • pp.541-549
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    • 2018
  • This paper deals with the braking dynamic behavior of diesel electric locomotive pulling domestic cargo and passenger vehicles. Friction coefficient, pneumatic pressure, and running resistance affecting the braking system were tested. For the friction coefficient, the Dynamo test was performed with reference to UIC 541-4. The results are analyzed by multivariate regression and the relationship between braking force and ititial velocity is presented. The pneumatic pressure were classified into service braking and emergency braking. In order to reflect the characteristics of the brake valve and piping, the pressure rising over time was measured in the vehicle. In order to reflect the external force acting on the vehicle, we carried out the test of EN 14067-4 and presented the second order polynomial formula on a running resistance. The running resistance test results were compared with other countries. The dynamic behavior of a diesel electric locomotive running on a straight flat track based on vehicle resources, friction coefficient, braking pressure, and running resistance is simulated using the time integration presented in EN 14531-1. The simulation results were compared and verified with the vehicle braking test results. The results of this study can be used to analyze the dynamic braking behavior of a train. Also, it is expected that various parameters affecting braking in vehicle design can be analyzed and used as basic data for braking performance improvement.

A Study on Calculation of Engine Torque for Automotive (자동차의 엔진 토오크 산출에 대한 연구)

  • 나완용
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.4
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    • pp.211-219
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    • 2003
  • The main study experiments to obtain engine torque of the vehicle during performance test of the recent automobile. Torque was measured through the engine dynamometer to produces engine torque of the vehicle but the research method calculated engine torque of the vehicle without the engine dynamometer. The performance of the vehicle receive various running resistance. The study certificates performance of certification before a certification of used vehicle didn't carry out and certificate. This way evaluated on road test and chassis dynamometer The result of the study shows that it is much possible to apply the test. After comparing the engine torque of road driving with that of chassis dynamometer, the results are approximately the same. When rapidly speeded up, the road-load vehicle can pitch in some degrees, which may result in the fluctuations of acceleration, and then affect on the engine torque. Therefore it is confirmed that this method is easier way to measure the performance of vehicles.

Development of Free Running System for 2m-class Ship Models (2m급 모형선용 자유항주시스템 개발)

  • Shin, Hyun-Kyoung;Kim, Min-Sung
    • Journal of the Society of Naval Architects of Korea
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    • v.45 no.3
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    • pp.247-257
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    • 2008
  • In this paper, a free running system, which is developed recently for a 2m-class ship models, will be introduced. For the remote control of hardware, GUI of software packages was developed using Visual Basic 6.0, and Host PC with Positioning Board manages Servo drive. Then the drive operates propeller and rudder. Its control performance will be shown. Also its adaptability to the resistance, manoeuverability and seakeeping model tests will be considered through the installation on a KTTC standard ship model from MOERI.

Performance Predictions for Sailing Yacht by Towing Tests and VPP Calculation (예인수조 시험 및 VPP 계산에 의한 세일링 요트의 성능 추정)

  • Yoo Jae-Hoon;Ahn Hae-Seong
    • Journal of Advanced Marine Engineering and Technology
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    • v.30 no.1
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    • pp.116-124
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    • 2006
  • A model test was carried out, in order to verify the hydrodynamic performances of public 30 feet class sailing yacht. In the initial design stage, the performances and the running attitude of sail yacht including the hull form and sail plan, appendages were estimated by VPP, from which made the representative test conditions. A new experiment system such as captive model device was composed because the running attitude could be changed by wind conditions. The test results show that the minimum resistance is generated in the heeling 20 degree. which was expected in the initial design stage. It is thought to be the useful informations that the keel has an effects on hydrodynamic forces and resistance differences between the upwind and the downwind condition. Also this paper is associated with the state-of-the-art of calculating sailing yacht performance as this is performed in velocity Prediction program (VPP) The VPP results shows a typical shape of a sailing yacht and the designed yacht has the best performance at 120 degree angle of true wind with 20 knots.

Performance Predictions for Sailing Yacht (세일링 요트의 성능 추정에 관한 연구)

  • Yoo, Jae-Hoon;Ahn, Hae-Seong
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2005.06a
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    • pp.824-831
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    • 2005
  • A model test was carried out, in order to verify the hydrodynamic performances of public 30 feet class sailing yacht. In the initial design stage, the performances and the running attitude of sail yacht including the hull form and sail plan, appendages were estimated by VPP, from which made the representative test conditions. A new experiment system such as captive model device was composed because the running attitude could be changed by wind conditions. The test results show that the minimum resistance is generated in the heeling 20 degree, which was expected in the initial design stage. It is thought to be the useful informations that the keel has an effects on hydrodynamic forces and resistance differences between the upwind and the downwind condition. Also this paper is associated with the state-of-the-art of calculating sailing yacht performance as this is performed in velocity prediction program (VPP). The VPP results shows a typical shape of a sailing yacht and the designed yacht has the best performance at 120 degree angle of true wind with 20 knots.

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Experimental Study on the Hydrodynamic Forces of 30 Feet Sailing Yacht (30피트급 요트의 유체력에 대한 실험적 연구)

  • Yoo, Jae-Hoon;Ahn, Hae-Seong
    • Journal of the Society of Naval Architects of Korea
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    • v.42 no.3
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    • pp.233-240
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    • 2005
  • A model test was carried out, in order to verify the hydrodynamic performances of public 30 feet class sailing yacht. In the initial design stage, the performances and the running attitude of sail yacht including the hull form and sail plan, appendages were estimated by VPP, from which made the representative test conditions. A new experiment system such as captive model device was composed because the running attitude could be changed by wind conditions. The test results show that the minimum resistance is generated in the heeling 20 degree, which was expected in the initial design stage. It is thought to be the useful informations that the keel has au effects on hydrodynamic forces and resistance differences between the upwind and the downwind condition.

A Study on Balanced -type Oseillating Mole-Drainer(III)-Model Test for Draft Force, Torque, Power and Moment (평행식 진동탄환 암거 천공기의 연구(III)-견인력, 토크, 동력 및 모멘크에 관한 모형시험-)

  • 김용환
    • Journal of Biosystems Engineering
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    • v.1 no.1
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    • pp.1-6
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    • 1976
  • This paper is the third one of the study on balanced type oscillating mole-drainer, the first one was presented in No 9. Gyeongsang College Report and the second one in Vol. 17, No.4 of the KSAE. In the first part of this study, the characteristics of traction forces between the nonoscillating earth working equipments and oscillating ones was compared. A model of the balanced type oscillating mole-drainer, which composed of a mechanism that may reduce the machine vibration, was designed following the dimensional analysis and similitude technique. The model test was carried out to clarify the balancing mechanism of the oscillating parts and other parts of the machine. In the light of the results from the model tests, a prototype machine was made for experimental purpose. Results from the field test by a reported in the near future. In the second report, the model tests were carried out under the same soil conditions, i.e, . oscillating frequency, running velocity, and oscillating amplitude, etc. It was clear that use of balanced type oscillating model could substantially reduce the vibration of the whole system of the machine, when compared with the nonoscillating type model. In this paper(the third report), results of investigation on the traction force, power requirement, and moment. etc, is presented. Analysis of variance technique was used for analyzing the effect of the frequency, amplitude, and running velocity on the draft force, torque, power requirements, and moments. The results obtained from the model tests are as follows, 1) By practicing a balanced-type oscillating mole-drainer, it was possible to reduce the traction resistance by 55.1-61. 2 percent of traction resistance, however, was 1.75 - 1.95 times greater than the value of resistance which was induced by use of a mole-drainer with single bullet. The resistance of rear shank against soil was considered as a main causing factor of the above results. 2) As the oscillation frequency was increased, the traction resistance was decreased. Considering on the effect of oscillation the greater the amplitude, and the slower the running velocity was, the greater the reduction ratio of traction resistance was. 3) The ratio of the traction resistance of oscillating mole-drainer to that of non-oscillating one could be represented as a function of dimensionless variable (V/$Af$). The results from the tests were well agreed with the reported results from the experim ents on oscillation plow or hoe. 4) By taking a lower value of (V/$Af$), reducing the traction resistance was possible. This fact meant, however, that the efficiency of mole drain practice would be lower. 5) It was experimentally confirmed under the same condition of soil that the variable (R/$rD1^3$) could be represented as a function of a variable($V^2/gD$) when a non\ulcornerocillating mole-drainer was used. 6) When a oscillating mole-drainer was used, the variable(R/$rD_1^{3}$) could be represented as a function of two variables ($v^2/gD_1$) and (V^2/gD_1$). 7) The torque was not affected by a change of frequency. However, a relation of proportionality existed between torque and amplitude, running velocity, and ratio of bullet diameter. When a balanced type oscillating mole-drainer with two bullets was used, torque was increased by 52.8-78. 4 percent and total power requirement was also increased. 8) Total power requirement was increased linearly in accordance with the increasing frequency, 41.96 percent of total power was used for oscillating action. The magnitude of total power requirement was 1. 8-9. 4 times greater than that of a non-oscillating mechanism. In the view point of power requirement, it was not advisable to increase the frequency, amplitude, running velocity, and ratio of bullet diameter at the same time. 9) Only the positive moment occured in the rear shank. Change of the diameter of a rear bullet, could not affect the balancing against the soil resistance. It was necessary for rear bullet to have a large resistance against soil only when the rear bullet was in backward motion. 10) Within an extent of the experimental base, optimum limits for several design factors were A=0.5cm, $f$=22.5Hz, V=O. 05m/sec, and $\lambda$=1.0 By adapting these values traction resistance was reduced by 40 percent and vibration acceleration wa s reduced by 60 percent. Even though the total , power requirements for operating a balanced type oscillation mechanism was greater ~than that of non-oscillating one, using a oscillating mechanism would be more effective. Because a balanced type oscillating mechanism is used, tractive resistance will be reduced and then the lighter . tractive equipment could be used.

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