• Title, Summary, Keyword: Trim angle

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The Analysis of the Ship's Maneuverability According to the Ship's Trim and Draft (선박 TRIM변화에 따른 조종성능의 분석)

  • PARK, Byung-Soo;KANG, Donghoon;KANG, Il-Kwon;KIM, Hyun-Mu
    • Journal of Fisheries and Marine Sciences Education
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    • v.27 no.6
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    • pp.1865-1871
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    • 2015
  • Ship's trim is the one of the most important factor for safety at the sea. Turning circle test and Z-test were carried out to find the effect of ship's trim and draft changes. The results are as follows. 1. If the ship's draft and trim became large, turning circle would be wide. 2. If the ship's draft and trim became large, ship's drift angle would be small. Small drift angle made wide turning circle. 3. Trim by the head made slow ship's final speed when turning circle test. 4. By Z-test, the deeper draft and trim by the stern made small OSA. Small OSA means strong ship's stability. 5. Totally 2nd OSA is smaller than 1st OSA on Z-test. 6. There were small differences of 2nd OSA in trim by the stern, but there were large OSA in trim by the head. 7. The larger trim by the stern, the smaller OSW. The small OSW means better ship's stability and maneuverability.

A Study of the Shearing Force as a Function Trim Punch Shape and Shearing Angle (트리밍펀치 형상과 전단 각에 따른 전단하중 특성에 관한 연구)

  • Yoo, C.K.;Won, S.T.
    • Transactions of Materials Processing
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    • v.24 no.2
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    • pp.77-82
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    • 2015
  • By investigating the practical use of trim punch configurations for shearing of vehicle panels, the current study first reviews the shearing angle as part of the shearing die design. Based on this review, four different types of trim punch shapes (i.e., horizontal, slope, convex, and concave type) and shearing angles(i.e., 0.76°, 1.53°, 2.29°, 3.05°, 3.81°) were investigated. In order to conduct shearing experiments, four types of trim punch dies were made. The four trim punch dies were tested under various conditions. The experiments used the four trim punch shapes and the five shearing angles. The shearing force varied by shape and decreased from horizontal, slope, convex, to concave for the same shearing angle. The magnitude of shearing force showed differences between the convex and the concave shapes due to the influence of constrained shearing versus free shearing. The test results showed that compared to the horizontal trim punch shearing force, the decrease of the slope, convex, and concave shearing forces were 22.6% to 60.4%. Based on the results, a pad pressure of over 30% is suggested when designing a shearing die.

The Effect of Divergence Angle on the Control Valve Trim Characteristics (확산각이 밸브 트림 특성에 미치는 영향)

  • Go, Tae-Sig;Kim, Kuisoon
    • The KSFM Journal of Fluid Machinery
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    • v.16 no.1
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    • pp.32-39
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    • 2013
  • The multi-stage control valve is one of the devices which controls cavitation and high pressure drop. To attain the high pressure drop, the conventional control valves adopted the multi-stage trim to avoid the occurrence of local cavitation in valves. This work studied the effect of divergence angle on the characteristics of multi-stage trim. Pressure drop and flow characteristics was calculated for the 1 passage of multi-staged trim by using the FLUENT 6.3.26. The result showed that the pressure drop is significantly influenced by the divergence angle of multi-stage trim. In addition, the pressure drop increased consistently as the Reynolds number and divergence angle increases.

Prediction of the Effects of the Ship's Heel and Trim Conditions on the Fire Development Characteristics (선박의 종경사 및 횡경사 변화가 화재 확산에 미치는 영향 예측)

  • Kim, Byeol;Hwang, Kwang-Il
    • Journal of Navigation and Port Research
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    • v.42 no.4
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    • pp.283-290
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    • 2018
  • Due to the environmental factors of the sea, ship accidents always contain an inclination angle. The change in the ship affects not only the evacuation speed of passengers but also the fire growth in the ship. For this reason, when analyzing the fire, it is necessary to analyze the risks by considering conditions of inclination. In this study, the temperature that affects the fire was calculated by alteration of ship's heel and trim angle and analyzed using FLUENT. Based on fire occurrence position, evacuation should be done within 37 seconds under the condition of $-10^{\circ}$ heeling angle and 36 seconds under the condition of $-10^{\circ}$ trim angle. However, it was predicted that the evacuation will not be affected under the conditions of $+10^{\circ}$ heel angle and $+10^{\circ}$ trim angle. For these reasons, it is confirmed that when the ship is on fire, evacuation measures should be considered based on the heel and trim conditions as per the location of the fire.

Optimized Trim and Heeling Adjustment by Using Heuristic Algorithm (휴리스틱 알고리즘을 이용한 트림 및 힐링 각도 조절 최적화)

  • HONG CHUNG You;LEE JIN UK;PARK JE WOONG
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.62-67
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    • 2004
  • Many ships in voyage experience weight and buoyancy distribution change by various reasons such as change of sea water density and waves, weather condition, and consumption of fuel, provisions, etc . The weight and buoyancy distribution change can bring the ships out of allowable trim, heeling angle. In these case, the ships should adjust trim and heeling angle by shifting of liquid cargo or ballasting, deballasting of ballast tanks for recovery of initial state or for a stable voyage. But, if the adjustment is performed incorrectly, ship's safety such as longitudinal strength, intact stability, propeller immersion, wide visibility, minimum forward draft cannot be secured correctly. So it is required that the adjustment of trim and heeling angle should be planned not by human operators but by optimization computer algorithm. To make an optimized plan to adjust trim and heeling angle guaranteeing the ship's safety and quickness of process, Uk! combined mechanical analysis and optimization algorithm. The candidate algorithms for the study were heuristic algorithm, meta-heuristic algorithm and uninformed searching algorithm. These are widely used in various kinds of optimization problems. Among them, heuristic algorithm $A^\ast$ was chosen for its optimality. The $A^\ast$ algorithm is then applied for the study. Three core elements of $A^\ast$ Algorithm consists of node, operator, evaluation function were modified and redefined. And we analyzed the $A^\ast$ algorithm by considering cooperation with loading instrument installed in most ships. Finally, the algorithm has been applied to tanker ship's various conditions such as Normal Ballast Condition, Homo Design Condition, Alternate Loading Condition, Also the test results are compared and discussed to confirm the efficiency and the usefulness of the methodology developed the system.

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Evaluation of Longitudinal Static Stability of Human Powered Hydrofoil Boat (인력 수중익선의 정적 종안정성 평가)

  • Choi, Jung-Kyu;Kim, Hyoung-Tae
    • Journal of the Society of Naval Architects of Korea
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    • v.46 no.4
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    • pp.391-397
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    • 2009
  • In this paper, longitudinal static stability is investigated, which is an essential requirement for the safety and the performance of the human powered hydrofoil boat (HPHB). In case a disturbance changes the trim angle of the boat, the derivative of the moment about the center of gravity must be negative in order to make the boat to be stable. The equation to evaluate the longitudinal static stability of the EPISODE, a HPHB of Chungnam National University with a height controlling system(HCS) is derived. From the derivative it is confirmed that a longitudinal and vertical position of the center of gravity is important for a HPHB. The range of a trim angle while the boat is foil-born was found with a HCS under the condition of mechanical restraint. And it is confirmed that the longitudinal static stability is satisfied for EPISODE in certain range of a trim angle. It is also shown that the longitudinal static stability and a range of the trim angle can be determined from the principal dimensions of a HPHB, therefore, it can be applied from the stage of the conceptual design of HPHB.

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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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.

Power and Trim Estimation for Helicopter Sizing and Performance Analysis

  • Laxman, Vaitla;Lim, Jae-Hoon;Shin, Sang-Joon;Ko, Kwang-Ho;Jung, Sung-Nam
    • International Journal of Aeronautical and Space Sciences
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    • v.12 no.2
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    • pp.156-162
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    • 2011
  • The preliminary design stage of helicopters consists of various operations and in each operation design several detailed analysis tasks are needed. The analysis tasks include performance and the required power estimation. In helicopter design, those are usually carried out by adopting the momentum theory. In this paper, an explicit form of computational analysis based on the blade element theory and uniform/non-uniform inflow model is developed. The other motivation of the present development is to obtain trim and required power estimation for various helicopter configurations. Sectional and hub loads, power, trim, and flapping equations are derived by using a symbolic tool. Iterative computations are carried out till convergence is achieved in the blade response, inflow, and trim. The predictions regarding the trim and power estimation turn out to be correlated well with the experimental results. The effect of inflow is further investigated. It is found that the present prediction for the lateral cyclic pitch angle is improved with the non-uniform inflow model as compared to that by the uniform inflow model. The presently improved trim and power estimation will be useful for future helicopter sizing and performance analysis.

An Experimental Study on the Manoeuvrability of a Ship in Different GM and Trim Conditions (GM 및 종경사 변경에 따른 선박의 조종성능변화에 관한 실험적 연구)

  • Yun, Kunhang;Kim, Dong Jin;Yeo, Dong Jin
    • Journal of the Society of Naval Architects of Korea
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    • v.57 no.4
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    • pp.230-240
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    • 2020
  • The aim of this study was to investigate the manoeuvrability of a ship in different Center of Gravity (CG) conditions. Free Running Model Tests (FRMT), such as 35°turning circle tests, 20/20 zigzag manoeuvring tests, and 10/10 zigzag manoeuvring tests, were conducted in three GM and three trim conditions with 1/65.83 scaled KRISO Container Ship (KCS). The test results indicated that KCS in the lower GM condition and the trim by bow condition showed reduced advance and tactical diameter in turning circle tests and increased overshoot angles in zigzag tests, and those manoeuvring indices were strongly related with roll angle. In addition, sensitivity indices for three-axis CG position were suggested with prior research, and it showed that y-axis CG position significantly affected manoeuvrability of KCS due to the low GM. Therefore, in the case of KCS, it is evident that the roll angle during manoeuvre is closely related with manoeuvring indices.