• Journal of Navigation and Port Research
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• v.38 no.5
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• pp.463-470
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• 2014

In this paper, calculation of towing force required to tow the ship and experiments to verify its appropriacy are discussed. Friction, wind and wave-making resistance of vessel are considered to calculate towing force of specified vessel. Propeller resistance is also reflected and it is assumed that the propellers are locked. Node analysis to estimate additional resistance on towline is applied. Total towing force could be obtained by adding the ship's resistance and towline resistance. Experiments with training ship SAE YU DAL was executed to check the effectiveness of calculation methods and some comparison between experiments and calculation results was also done. From the comparative analysis, we confirmed that towing speed is primary terms in the calculation of towing force and propeller resistance is a major elements of ship's resistance with the increasing of towing speed. We can see that additional resistance induced by yawing of ship during towing have to be considered for total tow resistance.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.12-23
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• 2021

In the conventional experiment to assess the towing operations, the towing stability of the towed vessel has been evaluated under the condition without lateral motion of the tug-boat. However, the tug-boats may have a lateral force to change the direction of the towed vessel. In this study, experiments have been conducted considering unsteady conditions in the towing system. First, a towing test system in a Circular Water Channel (CWC) using the conventional experimental method is built. Second, the towing characteristics of the towed vessel are investigated using the conventional method, and they are compared with other research results and stability discriminant criteria. Third, the lateral motion of the tug-boat was modeled as a sinusoidal motion using a forced oscillation device changing frequency and amplitude. Finally, the discussion is given in terms of both towing- and course-stability of the towed vessel according to the lateral motion of the tug-boat.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.41 no.2
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• pp.122-128
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• 2005

The experiments were conducted to fine out the handling characteristics of the FMT(Frame Mideater Trawl) in the southern waters of Korea using a trawler "DONGBAEK" belongs to Yosu National University. The realtionship between the net depth D(m) and the warp length L(m) at the towing speeds of 2.5k't and 3.5k't werw as follows ; D(m) = 0.30L - 1.3(2.5k't), D(m) = 0.16L - 1.5(3.5k't). Therefore, the net depth was 3.0m deeper when the warp length was 10m longer at the towing speed of 2.5k't and was 1.6m deeper for 10m longer at the speed of 3.5k't, respectively. The sinking speed of FMT was 6.5m/min when the warp releasing speed was 24m/min at the towing speed of 2.5k't and was 3.8m/min for 25m/min at the towing speed of 3.5k't, respectively. The rising speed of FMT was 6.9m/min when the warp rewinding speed was 28m/min at the towing speed of 2.5k't and was 5.3m/min for 25m/min at the towing speed of 3.5k't, respectively. The mean elapsed time getting to the stable towing condition was 104sec at the towing speed of 2.5k't and was 105sec at the towing speed of 3.5k't, respectively, and there was no time difference for the towing speed variation. During the towing, the net depth was comparatively stable on the condition of no change for the warp length and the towing speed.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.6
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• pp.407-413
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• 2013

In the conventional towing tank, the ordinary towing carriage has a speed barrier which caused not only by the limitation of the length of towing tank but also the limitation of acceleration. Therefore the length of the towing tank should be decided carefully from the planning stage of the towing tank construction. Consequently the acceleration of the towing carriage should be taken less than 0.06g practically to avoid the slip of the wheel on rail. Due to the increasing demand of the high speed experiments on the development of special novel ship, the requirement of the high speed towing carriage is continuously increased recently. When the minimum measuring time of the towing experiment is prescribed as five seconds, the carriage should be accelerated with higher than 0.12 g to get the speed of 18 m/sec even in the towing tank having a length of 400m in length approximately. This means that the requirement of acceleration is bigger than twice of the ordinary practices of carriage acceleration. In such a condition the exerted total power of motor could not converted to traction force for the acceleration of the carriage without slip. To over come these difficulties a pair of horizontal traction wheels are reinforced to each of the ordinary vertical carrier wheel and appropriate suspension system has been devised for the towing tank of super high speed operation. It is believed that the design of novel suspension system adaptable for the high speed acceleration of towing carriage will play a important role as a reference for the remodeling of the towing tank for high speed experiment.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.3
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• pp.351-360
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• 2014

The experiments were carried out to decide the selective fishing gear of the shrimp beam trawl fishery. The model nets were made of General type, Double-level type and Grid type. The model experiments were carried out to test opening efficiency and towing tension. The experimental tanks were the flume tank [$8.0L{\times}2.8W{\times}1.4H(m)$] and the towing tank [$85L{\times}10W{\times}3.5H(m)$] in National Fisheries Research and Development Institute. The full scale experiments were carried out to compare the selectivity of General type net, Double-level type net and Grid type net in the southern sea of korea. The vertical opening (net height) of the model nets can be expressed as a function of the towing velocity as the straight line. The towing tension of the model nets can be expressed as a function of the towing velocity as the parabola. The shrimp catching rates of upper cod end in Boryeong and tongyeong were 78%, 9% respectively, but the rates of lower cod end were 23%, 91% respectively. The number bycatch rates of General type and Grid type were 23%, 11% respectively, and the weight bycatch rates were 34%, 31% respectively. A selective shrimp beam trawl net is Grid type in korea coastal sea.

• Journal of Ocean Engineering and Technology
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• v.27 no.1
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• pp.67-73
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• 2013

This paper presents the results of a numerical study on the towing stability of barges. Towing simulations were carried out by using two different numerical models (MMG model and cross-flow model). Stability criteria are also suggested based on the analysis of the linearized governing equations for towed vessel motion. In order to validate the present numerical models, the experimental data of Yasukawa et al. (2006) were used. Simulations were conducted for single and double barges under constant towing speed and direction conditions. The time histories of the heading angle, yaw rate, and towline tension were compared between the numerical results and experiments. The effects of the towline length on the slewing frequency and maximum heading angle were also observed. In addition, a series of numerical simulations using variable hydrodynamic coefficients were performed to investigate the effects of the hydrodynamic forces on the towing stability.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.373-379
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• 2016

Hydraulic forces on a vessel are changed according to the depth/draft ratio (h/d) during berthing or towing in a lateral direction. It is well known that lateral current force coefficient is dependent on the kinds of vessel in question. However, not much research exists about the characteristics of general ships, except for oil tankers, as suggested by the Oil Companies International Marine Forum (OCIMF). In this paper, lateral current coefficient related to h/d is analyzed in comparison with theoretical values and experiments with a 93m passenger ship. The estimated total resistance on the ship was 14.0 tons under an h/d of 1.6 with a lateral current force coefficient of 1.9. This was found to be similar to the measured value of 13.8 tons on the towing line in actual experiments. Resistances on the ship under an h/d of 3.0 was calculated to be 19.9 tons with a lateral current force coefficient of 1.3. Therefore, the lateral current force coefficient was expected to be 1.3 under an h/d of 3.0, in experiments measured value 20.0 tons. And the discharging currents did not affect the towing force if the towing line was over 30 m, since the towing resistance showed a similar tendency for changes in line length from 30 m to 60 m.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.1
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• pp.45-58
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• 2002

In this paper, we designed the circuit of drive control for towing winch. It is composed of reference voltage circuit for driving voltage reference, low pass filter circuit for noise reduction, dead zone circuit for initial transient input, and driving circuit for drum direction/velocity control. Also it is realized a drive control circuit for towing winch drum in accordance with PWM(pulse width modulation) method to suit it's purpose of a large capacity driving system. The performance of the designed circuit is analyzed by experiments and the appliablity for driving the towing winch drum satisfactorily is evaluated through a various testing.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.2
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• pp.140-149
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• 2008

This study evaluated the efficiency of an oil fence and spreading devices for one vessel in a towing tank. A series of model experiments and numerical calculations were conducted using an existing oil fence for two vessels and a new method for one vessel. Models of the oil fence and spreading devices were constructed on $1/20^{th}$ scale from waterproofed nylon fabric and canvas. The tensions acting on the model of the oil fences and the horizontal distance between the spreading devices were calculated numerically while the oil fences were being towed. The results were extremely close to the results of the model experiments. The ratio of the opening width to the total length of the oil fence, which shows the efficiency of the oil fence for one vessel, was 49.7% in 0.4 m/sec. Therefore, the proposed oil fence system should be very useful for oil containment at sea. As the opening width of the oil fence is not proportional to the length of the towing rope, it may be reasonable to maintain the towing rope at approximately 100 m. Furthermore, a reasonable towing speed, when operating the oil fence for one vessel equipped with spreading devices, was within 0.4 m/sec.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.579-585
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• 2019

Increasing the detection probability of underwater targets necessitates securing the towing stability of the active towed SONAR. In this paper, to confirm the effects of tail wing fin on towing attitude and towing stability, two scale model experiments and one sea trials were conducted and the results were analyzed. The scale model tests measured the towing behavior of each of the tail fin shapes according to towing speed in a towing tank. The shape of the tail fin used in the scale model test was tested with an I-type tail fine and four Y-type tail fins, totaling five tail fins of the two kinds. The first scale model test confirmed that the Y-type tail fin was superior to the I-type tail fin in towing attitude and towing stability. The second scale model test confirmed the characteristics of the vertical tail fin height increase and the lower horizontal tail fin inclination angle application shape based on the Y-type tail fin. The shape of the application of the lower horizontal tail fin inclination angle showed the best performance. In order to verify the results of the scale model test, a full size model was constructed, sea trials were performed, and the towing attitude was measured. The results were similar to those of the scale model test.