• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.56 no.2
• /
• pp.172-182
• /
• 2020

In order to offer specific information needed to assist in operation of a ship with same type rudder through evaluating the maneuverability of training ship A-Ra with flapped rudder, sea trials based full scale for turning test, zig-zag test with rudder angle 10° and 20°, and spiral test at service condition were carried out on starboard and port sides around Jeju Island according to the standards of maneuverability of IMO. As a result, the angular velocity of port turn was higher than that of starboard turn. Therefore, the size of turning circle was longer on the starboard side. In addition, variation of the transfer due to various factors was more stable than those of the others. In the Z-test results, the mean of 1st and 2nd overshoot angles were 9.8°, 6.3° and 15.3°, 9.2° respectively when the port and starboard was 10°; the 1st overshoot angle were 18°, 13.7° when using 20°. Her maneuverability index T' and K' can be easily determined by using a computer with the data obtained from Z-test where K' and T' are dimensionless constants representing turning ability and responsiveness to the helm, respectively. In the Z-test under flap rudder angle 10°, the obtained K' value covered the range of 2.37-2.87 and T' was 1.74-3.45. Under the flap rudder angle 20°, K' and T' value showed 1.43-1.63, 1.0-1.73, respectively. In the spiral test, the loop width was unstable at +0.3° and -0.5°-0.9° around the midship of flap rudder. As a result, course stability was comparatively good. From the sea trial results, training ship ARA met the present criterion in the standards of maneuverability of IMO.

• Proceedings of KOSOMES biannual meeting
• /
• 2018.06a
• /
• pp.129-129
• /
• 2018

• Journal of the Society of Naval Architects of Korea
• /
• v.43 no.5 s.149
• /
• pp.568-577
• /
• 2006

With the increase of ship size and speed, the loading on the propeller is increasing, which in turn increases the rotational speed in the propeller slipstream. The rudder placed in the propeller slip stream is therefore subject to severe cavitation with the increased angle of attack due to the increased rotational induction speed of the propeller. In the present paper the surface panel method, which has been proved useful in predicting the sheet cavitation on the propeller blade, is applied to solve the cavity boundary value problem on the rudder. The problem is then solved numerically by discretizing the rudder and cavity surface elements of the quadrilateral panels with constant strengths of sources and dipoles. The strengths of the singularities are determined satisfying the boundary conditions on the rudder and cavity surfaces. The extent of the cavity, which is unknown a priori, is determined by iterative procedure. Series of numerical experiments are performed increasing the degree of complexity of the rudder geometry and oncoming flows from the simple hydrofoil case to the real rudder in the circumferentially averaged propeller slipstream. Numerical results are presented with experimental results.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.24 no.4
• /
• pp.482-488
• /
• 2018

Generally, after stern tube bearing shows a significant increase in local load due to propeller load, which increases the potential adverse effects of bearing failure. To prevent this, research on regarding shaft alignment has been carried out with a focus on reducing the relative slope between the shaft and support bearing(s) under quasi-static conditions. However, for a more detailed evaluation of a shafting system, it is necessary to consider dynamic conditions. In this context, the results revealed that eccentric propeller force under transient conditions such as a rapid rudder turn at NCR, lead to fluid-induced instability and imbalanced vibration in the stern tube. In addition, compared with NCR condition, it has been confirmed that eccentric propeller forces given a rapid rudder starboard turn can lift a shaft from the stern tube bearing in the stern tube, contributes to load relief for the stern tube bearing.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.22 no.2
• /
• pp.22-30
• /
• 1986

It is very important for a navigator on bridge to know the maneuverability of his ship sufficiently at sea. Generally, the data of a turning circle test have long been used to study and evaluate the maneuverability of a ship. But referring only the data of the turning circle test method, he can not evaluate his ship's maneuvering characteristics sufficiently. So nowaday the test method added Z test to turning circle test for more detail references is considered to be desirable. In this paper, the authors performed PAL test and Z test together in order to study the maneuverability of M. S.Pusan 403, training ship of the National Fisheries University of Pusan. According to the results of PAL test, the rudder effect in port rudder angle of the M. S. Pusan 403 was found to be more effective than that in starboard one, because her changing amounts of angular velocity, turning radius and tangent speed in port rudder angles were found to be larger than those of them in starboard rudder one in unsymmetry. The relation between her drift angle(.8) and rudder angle (0) was found to be changing with .8=0.640 in direct proportion. As it appeared that her calculated K'-values were smaller than the standard K'-values of different kinds of ships in accordance with her Z test, her turning ability was found to be lower. The running distance of a turn in her 10$^{\circ}$ Z test was about 8.3 times her own length and was found not to be exceeded the standard maneuvering distance, therefore she was considered to have good maneuverabilities synthetically.

• Journal of the Korean Institute of Navigation
• /
• v.1 no.1
• /
• pp.27-44
• /
• 1977

The Maneuvering Indices of a ship are the values that decide the quantity of her motion in turning when her rudder is turned over to an angle to the starboard or the port. They consist of two kinds of indices, one of which is called index K and the other, index T. Index K decides a ship's turning ability and index T does the length of time delay of a normal turning motion after her rudder has finished the turn of an ordered angle. Generally, the values of the indices are calculated through some mathematic formulas with figures of her heading degrees recorded at a fixed time intervals during her Z test. The values of the same kind index of a ship appear differently according to the ship'sspeed, trim, rudder angle and loaded condition, etc. In this paper, the author analyzed all the amthematic formulas required to calculate the values of the indices in their forming process and examined them from the point of mathematics and dynamics and also actually figured out the values of maneuvering indices of the M.S. "HANBADA", the training ship of Korea Merchant Marine College through her Z test. The author supposed a case in which two same typed ships as the "HANBADA" in size, shape and conditions were approaching each other in meeting end on situation and each ship turned her rudder hard over to the starboard respectively when they approached to the distance of 3 times as long as the ship's length. The author worked out mathematic formulas calculating forward and transverse ship's motions within the above mentioned situation for the quantative analysis of the collision avoding action to certify whether they are in collision status or not. Applying the calculated values of the maneuvering indices of the "HANBADA" to the motion calculating formulas, the author found out the two ships were passing over each other with the clearing distance o 39m between their port quarters. With the above mentioned examinations and explanations, the author demonstrated that a ship's motion in any collision avoiding action can be shown with quantities of time and distance within reliable limit.istance within reliable limit.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.24 no.6
• /
• pp.701-708
• /
• 2018

Human error is an important cause of maritime accidents and the identification of human error is fundamental to maritime-accident preventions. In particular, the pattern of technical behavior taken in the circumstance of bridge teams(navigator & helmsman) provides important information to identify human error. The purpose of this study is to identify and analyze technical behavior pattern of bridge teams using Williamson's turn for rescue of persons overboard. The focus of this study is to build and analyze a cognitive model of the human behavior factors of the bridge teams in the process of implementing the experiments. The experimental environment was constructed using a ship-handling simulator and conducted an experiment on participants from 24 bridge teams. As a result of the experiment, it was able to identify the behavior pattern of the ship's maneuvering and maintain trajectory using the rudder and engine. This study is expected to correct human error in the bridge teams application to the certification and training of seafarers.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.22 no.1
• /
• pp.24-28
• /
• 1986

The maneuverabilities of the M. S. PUSAN 402 are studied, based on maneuvering indices and the data obtained from her Z test. The results obtained are summarized as follows: 1. The maneuvering indices K' and T' of the M. S. PUSAN 402 are 1. 490, 1.030 at 10$^{\circ}$ Z test and 2.644, 1.153 at 20$^{\circ}$ Z test and 3.382. 1. 027 at 30$^{\circ}$ Z test respectively. The above calculated values K', T' showed that her maneuverabilities are more increased when the rudder is used to large angle than to smaIl angle. 2. As her maneuvering indices K' and T' at 10$^{\circ}$ Z test are higher than the standard maneuvering indices of fishing boats, her turning ability was found to be higher but her obeying ability lower. 3. When the M. S. PUSAN 402 took a turn at her 10$^{\circ}$ test, running distance was about 8.4 times her own length and didn't exceed the standard maneuvering distance, 5 to 11 times ship's own length, therefore she was considered to have good maneuverabilities syntheticaIly.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2022.06a
• /
• pp.31-32
• /
• 2022

In Early vessels did not provide an exact equation for preventig the capsizing vessels. On land, many vehicle rollover prevention technologies using the steady-state Conrning Equations were developed, which showed better performance than the exiting method at sea. For better performance, It is proposed to improve safety mangement when turning vessel using the Ackerman geometic model-based Cornering Equations in this paper.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2019.11a
• /
• pp.269-269
• /
• 2019

The ships are turning for the purpose of collision avoidence and change of course. It is possible that ships have capsizing accident when improper loading of cargo and excessive use rudder angle in turning. It is difficult for navigation officers to recognize the danger of heeling during a turn, because the dynamic state of the ship changes in real time. Thus, in this study, ship's heeling angle was predicted during turning using the maneuverability indices estimated from the ship's autopilot. The maneuverability indices estimated through the Kalman filter of Autopilot is real-time predictable. The turning radius was obtained from the estimated Index of turining ability and calculations of the heeling angle were possible in turning. It is intended to be used as a basic data on the prevention of danger heeling angle during turning.