• Title, Summary, Keyword: 횡동요

Search Result 104, Processing Time 0.025 seconds

Experiment and Simulation Study on Performance Evaluation and Design of Fin-Stabilizer (핀 안정기 설계와 성능평가를 위한 모형시험과 시뮬레이션 연구)

  • Cho Seok-Kyu;Hong Sa-Young;Jang Taek-Su
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.41 no.6
    • /
    • pp.1-7
    • /
    • 2004
  • Recently, very large container ships are emerging as shipment of containers is expected to rapidly increase near future. A possibility of roll resonant motion in a seaway is expected to noticeably increase for large container ships of which capacity ranges 8,000 to 15,000 TEU due to relatively wide breadth and shallow draft comparing to conventional container ships. In this paper, a design and performance evaluation of a fin stabilizer for a 9,000 TEU container ship is carried out. The weak opposed control concept is adopted for the design. Time domain simulations and model tests are performed for performance evaluation. The design prediction, the model tests and the simulations show generally good agreements.

Design of Control Algorithm for Mass Driving Anti-Rolling System Considering Control Input Constraint (제어 입력포화를 고려한 횡동요 저감장치용 제어알고리듬 설계)

  • Moon, Seok-Jun;Lim, Chae-Wook;Lee, Hae-Jong
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.42 no.6
    • /
    • pp.566-574
    • /
    • 2005
  • Reduction of a ship's rolling is the most important performance requirement for improving the safety of the crew on board and preventing damage to cargos as well as improving the comfort of the ride. A mass driving anti-rolling system (MO-ARS) might be one candidate of several systems against the ship's rolling. As the movable range of the mass on the ship is finite, the control system must include restriction on the mass position to protect the device and the ship. This restriction usually causes windup phenomenon and control performance is deteriorated seriously. Two control algorithms, anti-windup control and saturated sliding mode control, are studied in this paper. Control performance and robustness problem are checked out by numerical simulations.

An Experimental Study on Mass Driving Anti-Rolling System for Ships (가동질량을 이용한 선박용 횡동요 저감장치에 대한 실험적 연구)

  • Moon, Seok-Jun;Jeong, Jong-Ahn;Yoon, Hyeon-Kyu;Lee, Gyeong-Joong;Ann, Seong-Phil
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.42 no.6
    • /
    • pp.666-672
    • /
    • 2005
  • Reduction of a ship's rolling is the most important performance requirement for improving the safety of the crew on board and preventing damage to cargos as well as improving the comfort of the ride. A mass driving anti-rolling system (MO-ARS) might be one candidate of several systems against the ship's rolling. In this paper, three types of MD-ARS, two passive and one active devices, are developed for small ships. After they are installed on the cabin of the small leisure boat, respectively, a series of performance test is conducted before and after operating them. Through the test, it is confirmed that the roll responses of the ship are pretty well reduced by the MO-ARS.

A Semi-Analytic Approach for Analysis of Parametric Roll (준해석적 방법을 통한 파라메트릭 횡동요 해석)

  • Lee, Jae-Hoon;Kim, Yonghwan
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.52 no.3
    • /
    • pp.187-197
    • /
    • 2015
  • This study aims the development of a semi-analytic method for the parametric roll of large containerships advancing in longitudinal waves. A 1.5 Degree-of-Freedom(DOF) model is proposed to account the change of transverse stability induced by wave elevations and vertical motions (heave and pitch). By approximating the nonlinearity of restoring moment at large heel angles, the magnitude of roll amplitude is predicted as well as susceptibility check for parametric roll occurrence. In order to increase the accuracy of the prediction, the relationship between righting arm(GZ) and metacentric height(GM) is examined in the presence of incident waves, and then a new formula is proposed. Based on the linear approximation of the mean and first harmonic component of GM, the equation of parametric roll in irregular wave excitations is introduced, and the computational results of the proposed model are validated by comparing those of weakly nonlinear simulation based on an impulse-response-function method combined with strip theory. The present semi-analytic doesn’ t require heavy computational effort, so that it is very efficient particularly when numerous sea conditions for the analysis of parametric roll should be considered.

ESTIMATION OF ROLL COEFFICIENT OF UNDERWATER VEHICLE USING A CALCULATION OF HYDRODYNAMIC FORCES (동유체력 계산을 이용한 수중운동체의 횡동요 계수 변화 예측)

  • Kim, T.W.;Kang, T.J.;Park, W.G.;Jung, C.M.
    • Journal of computational fluids engineering
    • /
    • v.20 no.2
    • /
    • pp.81-87
    • /
    • 2015
  • For Underwater vehicles, Unwanted roll excursions are inevitable as they are caused by induced propeller torque, disturbances, and banking motion during turns. To estimate the manoeuvring performance of underwater vehicle, it is necessary to obtain the roll coefficient of body. This paper was covered estimation of roll coefficient of underwater vehicle using STAR-CCM+, commercial CFD(Computational Fluid Dynamics) code. The RANS equations for incompressible fluid flows was solved numerically by using a finite volume method. An MRF(Moving Reference Frame) Method was Also adopted for rotations of body. For the validation, the flow around a DARPA SUBOFF bare hull model was simulated and good agreement with experiments was obtained. And Pure roll coefficients were calculated and campared with the experimental data which were presented by Seoul National University. Finally, an underwater vehicle model with propeller was simulated and analyzed for estimation of roll coefficient variation caused by induced propeller torque.

A Study to Improve the Performance of a Fixd Type Fin Stabilizer with Coanda Effect (콴다효과를 적용한 고정식 핀 안정기의 성능개선에 관한 연구)

  • Seo, Dae-Won;Lee, Se-Jin;Lee, Seung-Hee
    • Journal of Navigation and Port Research
    • /
    • v.37 no.3
    • /
    • pp.257-262
    • /
    • 2013
  • A ship operating in rough sea may suffer from an undesirable motion which may severely degrade the performance of equipment onboard and give a person an uncomfortable feeling. Hence, roll stabilization received a considerable attention and various devices including bilge keels, stabilizing fins, gyroscopic, anti-rolling tanks, rudders and flaps have been conceived and utilized for the purpose. The Coanda effect is evident when a jet stream is applied tangential to a curved surface of a hydrofoil since then the jet increases the circulation around the foil and consequently the lift. Model tests and numerical simulation have been conducted to examine the practicality of a fixed type fin stabilizer augmented by the Coanda jet. The results show that the lift coefficient of the modified Coanda fin at the zero angle of attack identically coincides with that of the original fin at ${\alpha}=\26^{\circ}$ when Coanda jet is supplied at the rate of $C_j$ = 0.25. It is also shown that fixed type fin stabilizers for active control of the motions of ships and the other mobile units without rotation can be put to practical use if the Coanda effect is applied.

On the Motion Characteristics of Small Trawler under Operation (소형 트롤 어선의 예망중 동요특성)

  • Lee, Chun-Ki;Kang, Il-Kwon;Kim, Jeong-Chang
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.40 no.1
    • /
    • pp.65-72
    • /
    • 2004
  • This paper deals with an experimental study on the dynamical characteristics of ship motion during trawling job on the real sea. The experiments were carried out on the small stern trawler, and roll and pitch motion of the ship according to the wave directions were simultaneously recorded by P/C in the same sea conditions. From these data, the statistical properties and power spectra were obtained, and then the analysis of ship motion in trwal job was made. As a result, it was found that the pitch motions in trwal job were displayed low amplitudes on the whole, but the rolling motions were displayed high amplitudes relatively, and very high value on the beam and quartering sea especially. Also, the trial ship has a high extinction coefficient in the roll motion, compared with the rule of stability, but when wave height takes 2.5m over, it can induce the safety of ship to scare occasionally. Therefore, a usefull countermeasure for the safety of ship has to be made adequately.

Prediction of the Out-of-plane Motion due to the In-plane Excitation (평면내 방향 기진력에 의한 평면밖 방향 운동의 예측)

  • Oh, Il-Geun
    • Journal of Ocean Engineering and Technology
    • /
    • v.7 no.2
    • /
    • pp.141-149
    • /
    • 1993
  • 삼 자유도를 가진 부유물체의 동적 응답을 이론적으로 연구하였다. 평면내 방향 운동모우드에 대한 지배방정식을 선형화한 후, 그들의 조화해를 평명밖 방향 운동모우드의 방정식과 연성시켰다. 그렇게 해서 주어지는 방정식은 시간에 따라 변화하는 계수를 가진 형태로서, 평면밖 방향의 운동만을 보일 것으로 예측되는 부유물체가 평면밖 방향의 운동을 보일 수도 있음을 밝혔다. 동역학적 불안정성과 그 결과로 나타나는 평면밖 방향의 대진폭 운동을 보이고 있다. 본 결과는 주기적으로 동요하는 부유물체가 서로 연성된 운동을 하는 현상으로도 해석할 수 있다.

  • PDF

Parameter Identifications of Roll Maneuvering Coefficients Based on Sea Trial Data (해상 실측 자료를 이용한 횡동요 조종 계수 식별)

  • C.K. Kim
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.35 no.2
    • /
    • pp.29-37
    • /
    • 1998
  • Linear equations of motion for submersibles are one of the rest important design parameters, which are used as a governing equation for the shape design and the controller design. But, the estimated maneuvering coefficients in equations of motion by using empirical formulae, theoretical calculations or model tests might have some errors. Therefore the maneuvering coefficients should be verified from sea trial test. In this study, parallel extended Kalman filter method, Nelder & Mead Simplex method and genetic algorithm were applied to the parameter identification of roll maneuvering coefficients based on sea trial data. As a result, it was verified that Nelder & Mead Simplex method gave the most satisfactory results for the mathmatical models and the sea trial data used in this study.

  • PDF

Theoretical Analysis at One Degree-at-Freedom Model for Rolling at Ships with Focus on Capsize (횡동요에 기인하는 전복에 대한 1-자유도계 모형의 이론해석)

  • Lee, Seung-Joan
    • Journal of the Society of Naval Architects of Korea
    • /
    • v.43 no.1
    • /
    • pp.22-31
    • /
    • 2006
  • Recent studies have shown that the short time solution of the equation of motion for the rolling of ships is important in deciding the possibility of capsize of ships due to the excessive heel. Since most of known solutions for nonlinear equations of motion are long time or steady periodic solutions, here a simple way is described to get the short time solutions of the Duffing equation, which was chosen for deriving a criterion for the capsize of the ship. With the small external rolling moment, we first assume the state of the small damping and near resonance. Then, for cases when the frequency of the external moment is higher than the resonant one, an inequality was derived as a criterion for the capsize. This gives the range of the initial condition and the magnitude of the external moment which should be avoided for a ship to be safe from capsize. Furthermore, from the linearized equation, it is also shown that a simple and self-explanatory solution can be obtained consistent with that for the case of no damping, which yields the well-known linear growth with time.