• Title/Summary/Keyword: 트림변화

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Effect of Trim Variations on the Ship Structural Responses (트림변화가 선체 구조응답에의 미치는 영향)

  • Kwon, Young-Sub
    • Journal of Ocean Engineering and Technology
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    • v.6 no.2
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    • pp.55-70
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    • 1992
  • 트림변화에 의해서 발생하는 선체 구조응답을 고찰, 계산 결과를 요약하였다. 본 고찰로 부터 같은 크기의 선수, 선미 트림상태일지라도 많은 차이를 보였다. 이에는 중량분포의 효과가 특히 크게 작용함을 밝히었다.

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A Study on the Hydrodynamic Performance of High-Speed Vessel with Trim Tab Using Full-Scale CFD Simulation (실선 스케일 CFD 해석 기반 트림 탭이 부착된 고속선의 유체동역학적 성능 분석)

  • Lee, Jonghyeon;Park, Dong-Woo
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.27 no.5
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    • pp.656-665
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    • 2021
  • In this study, trim tabs were attached to end of stern hull of a small high-speed vessel of length approximately 10 m and Froude number 1.0 to improve resistance performance and passenger comfort. Before computational fluid dynamics (CFD) simulations to assess the performance according to various geometries of the trim tab, the scale effect had been found through a previous study, so full-scale simulations were performed. The trim tab chord length was set to 0.5 %, 1.0 % and 1.5 % of LPP, and its angle to base line was varied in intervals of 5°. It decreased trim by stern and flotation: the greater the angle and length, the greater was the effect. Then it had pressure resistance decreased and shear resistance increased, and reduction ratio of total resistance varied accordingly. The results of this study indicated that the resistance performance was improved about 27 % at optimal running attitude that was the trim by stern about 1.5°.

Sensor Fault Detection for Small Turboshaft Engine Considering Multiple Trim Conditions (다중 트림 상태를 고려한 소형 터보샤프트 엔진의 센서 고장 검출)

  • Seong, Sang-Man;Rhee, Ihn-Seok;Ryu, Hyeok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.11a
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    • pp.192-195
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    • 2008
  • A sensor fault detection method for small turbo shaft engine considering multiple trim conditions is proposed. This engine is used in a helicopter. Firstly, under multiple trim conditions, we derive the linearized models from a nonlinear model which includes engine, rotor and feedback control loop. As a fault detection method, we adopt the Kalman filter based method. To keep continuity of estimates between the changes of trim conditions, we reconfigure the initial values of state variables at trim changes. We detect the faults with two steps that when the first filter does not alarm the faults for some sensors, the second filter is runned for other sensor. Via some simulations we show that the proposed method works well under multiple trim conditions.

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A Study on the accuracy of speed measuring system by the Doppler effect -The error of speed single beam Doppler log over the ground by various trim- (Doppler 효과(效果)에 의한 속도계측장치(速力計測裝置)의 정도(精度)에 관(關)한 연구(硏究) -Single beam Doppler log의 트림 변화에 따른 대지속력(對地速力) 오차(誤差)-)

  • Kim, Koang-Hong
    • Journal of Fisheries and Marine Sciences Education
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    • v.9 no.2
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    • pp.179-187
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    • 1997
  • Doppler log and current meter are based on the measurment of the doppler effect. Ship's speed over the ground measured by means of doppler log effect of underwater ultrasonic intends to get infulence by the difference of sound velocity, the ship's course, the sea bottom inclination, the trim and tranducer installation etc. This paper investigated on the error of speed over the ground by change of the trim comparing the real speed obtained by the mile post with the speed of single beam type doppler log on the trainning ship Kyeongyangho. The results are as follows ; 1. Indicating speed of doppler log is very much greatly influenced on variation of trim, but the real speed is less affected variation by trim. 2. The range of variation and error of speed over ground are smallest when ship's trim is 2.15m trim by the stern.

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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.

Study on Performance Analyses on Coaxial Co-rotating Rotors of e-VTOL Aircraft for Urban Air Mobility (도심 항공 교통을 위한 전기동력 수직 이착륙기의 동축 동회전 로터의 성능해석 연구)

  • Lee, Yu-Been;Park, Jae-Sang
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.49 no.12
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    • pp.1011-1018
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    • 2021
  • This numerical study conducts the modeling and the hover performance analyses of coaxial co-rotating rotor(or stacked rotor), using a rotorcraft comprehensive analysis code, CAMRAD II. The important design parameters such as the index angle and axial spacing for the coaxial co-rotating rotor are varied in this simulation study. The coaxial co-rotating rotor is trimmed using the torque value of the upper rotor of the previous coaxial counter-rotating rotor or the total thrust value of the previous coaxial counter-rotating rotor in hover. The maximum increases in the rotor thrust is 1.84% for the index angle of -10° when using the torque trim approach. In addition, the maximum decreases in the rotor power is 4.53% for the index angle of 20° with the thrust trim method. Thus, the present study shows that the hover performance of the coaxial co-rotating rotor for e-VTOL aircraft can be changed by the index angle.

Study on Resistance Component of Container Ship According to Trim Conditions (트림 변화에 따른 컨테이너선의 저항성분별 특성 연구)

  • Han, Ki-Min;Park, Hyun-Suk;Seo, Dae-Won
    • Journal of Ocean Engineering and Technology
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    • v.29 no.6
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    • pp.411-417
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    • 2015
  • The shipping and shipbuilding industries have had business difficulties since the implementation of regulations on the CO2 emissions from ships by IMO and the occurrence of the global financial crisis in 2008. Under this global recession, most shipping firms have started to operate their fleets at slow steaming rates with the goal of improving the profit ratio per transported unit. This study analyzed the resistance performance of a 6,800 TEU container ship corresponding to its trim variation with slow steaming, compared with that at its original design speed. Two different grid systems were used for the numerical calculation, one that considered the free surface allowing the capture of the dynamic trim and one that did not. This made it possible to clearly classify each resistance component to provide useful information to hull-form designers. In addition, a form factor assumption method using CFD was used for a reasonable effective power prediction in compliance with the 1978 ITTC performance prediction method. It was found that the total resistance of a 6,800 TEU container ship was reduced by 2.6% in the case of a 1-m trim at the bow at 18 kn.

Resistance and Seakeeping Tests of a LOA 47.7m Class Catamaran (LOA 47.7m급 쌍동선의 저항 및 내항 시험)

  • H.H. Chun;Y.K. Chung;S.S. Chung;R.H. Chang;S.W. Ha;J.M. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.4
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    • pp.56-63
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    • 1999
  • The seakeeping and resistance tests of a 47.7m class catamaran are conducted in a towing tank with the 1/21.5 scale model. The effect of the trim tab on the resistance is investigated with the trim tab angle variations and the resistance and trim angle of the catamaran with the trim tab are compared with those without the trim tab. The heave and pitch motions are measured at the three full scale speeds in sea state of 3.4 and 5 and the vertical accelerations at five points on the deck are also measured. The measured accelerations are compared with the criteria of ISO 2631/3 and it is shown that the seakeeping performance of the catamaran is good.

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A Study on Trim Variation to Reduce the Required Power of 11,000TEU Container Ship in Operation Condition (운항조건에서 11,000TEU 컨테이너선의 소요마력 저감을 위한 트림변화 연구)

  • Lee, Joon-Hyoung;Chun, Jang-Ho;Kim, Myoung-Soo;Park, Beom-Jin;Yu, Yongwan;Lee, Young-Yeon;Ahn, Haeseong;Kim, Youngsun;Lim, Iljin
    • Journal of the Society of Naval Architects of Korea
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    • v.58 no.3
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    • pp.198-205
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    • 2021
  • In this paper, the effect of trim variation on the required power of 11,000TEU container ship was investigated under conditions considering the actual operation speed and draft. For each draft condition, the effective power (PE) and delivered power (PD) trends were investigated with changes in trim and ship speed. At this time, the displacement volume was fixed same as the value of the even trim condition and the both sinkage at the fore and after perpendicular are confirmed. The test ship speeds were determined by considering the operating speed. Both numerical and experimental methods were used to analyze the effects of trim variation. Numerical analysis results were used for evaluating the resistance performance, and the self-propulsion performance was estimated using experimental data obtained from model test.

Trim Range and Characteristics of Autorotation(I): Rotor Speed Limit and Pitch Range (자동회전의 트림 범위와 특성(I): 로터 스피드 한계와 피치범위)

  • Kim, Hak-Yoon;Choi, Seong-Wook
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.39 no.6
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    • pp.487-497
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    • 2011
  • Numerical analysis has been performed to investigate the rotor speed and pitch range variations when the airspeed is increased in autorotation. Transient Simulation Method(TSM) was used to obtain the steady states of autorotation. The rotor blade was analyzed by the two-dimensional compressible Navier-Stokes solver in order to adapt to the airspeed increase and the results were used in the transient simulation method. Meanwhile, the Pitt/Peters inflow theory was used to supply the induced velocity fields. For the prescribed torque equilibrium state, the combinations of velocity, shaft angle, and pitch angle were produced to investigate the rotor speeds and variable ranges. The rotor tip Mach number and rotor speed were correlated and the trim range of pitch angle was observed with respect to the shaft angle decrease.