The tow force of tugboat has been brought through the bollard pull test, it execute under the condition of calm water and no forward speed. However, since the tugboat usually works in waves, the towing ability has to be examined in waves. In case of shallow propeller immersion depth I/D (Immersion depth/ Propeller diameter ratio), it will be supposed that a tugboat caused the tow force reduction due to the propeller racing in waves. In this paper, we examine the characteristics of mean tow force of tugboat for various factors, such as I/D ratio, wave height, wave direction, towing speed, wave length/ship length ratio X/L, through ship model experiment. In the water tank experiment, two types of ship models are used, which equipment a single kort nozzle Propeller or twin Azimuth Drive Propeller (A.D.P), respectively. Main results are as follows; 1) The mean tow force Tm in calm water and in wave clearly decreased with shallow I/D ratio. 2) Concerning with the influence of wave direction, the mean tow force Tm decreased with the wave height in head waves, but Tm increased in follow waves. 3) The influence of the wave length/ship length ratio X/L and towline length on Tm was slight.

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The tow force of tugboat is brought through the bollard pull test that is executed under the condition of still water and no forward speed. This is only information relating to towing works, which is offered to tugboat operator and pilot. However, since tugboat always works in waves and with forward speed, it is needed to know practical the tow force in waves. But the characteristics of tow force in waves have not been studied in series. In our studies, the characteristics of the tow force in regular head waves are examined by water tank experiment using ship model. To make clear the above characteristics, we divide the directly measured tow force into two components, namely the mean tow force Tm and the fluctuating tow force amplitude Ta. And influences of such as the elevation of towline, wavelength, wave height, forward speed on the above analyzed Tm and Ta are revealed.

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In a harbor, vessels frequently need the assistance of tug boats, for example, when berthing, escorting or towing. These are a great help for vessels' navigation and for the traffic efficiency. There has been sparse research on the subject of tug boats, due to the specific character of tug boats' work. For the purpose of learning more about safe tug operation, we must know how often there are, or have been, near-misses for tug crew. In this study, we distributed more than 2,000 questionnaires to tug crew all over Japan and received the sufficient answers to analyze the point of problem. This will be a useful tool for enhancing safety and mutual understanding between the tug boat operators and the assisted vessel. From the collected results of those questionnaires, we could consider that the most of crew members of tug boat are aware of risks in many situations. Therefore, we propose that this fact should be made public, especially to those tug boat operators and also the assisted vessel side. In a final conclusion, our work for this study should be helpful to minimize the near-miss or improve the safety environment.

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Pilots and tugboat captains point out that the towing ability of tugboat clearly declines in waves. This is important comment on operating safe and effective berthing maneuver. However, results of model experiments using water tank indicated that the towing ability of tugboat in waves did not decline scarcely (ref. (2) and (3)). So we have to check the steady wave force such as the wave drifting force acting on a towed ship in waves. But the influence of waves on the wave drifting force has not been examined because the waves around berth are very small comparing with the size of towed ships and waves in the ocean. In this paper, the physical mechanism causing the wave drifting force is verified and next some characteristics of the wave drifting force are discussed using results of model experiments. And then the wave drifting force for full-size fhips is examined. Finally, it is noticed that the wave drifting force is one of important external forces similar to the forces due to the wind and the current, in berthing maneuver.

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Recently, the reduction of ship noise and underwater radiated noise has become animportant issue. Engines and Z-pellers (azimuth thrusters) are considered as major sources of noise, and a quantitative evaluation of each sound source is required. In this paper, the contributions of engine and Z-peller were evaluated by noise and vibration measurement results in a hybrid tug ship. In order to predict the structure-borne noise level from the engine, an excitation force measurement was performed for both rigid and rubber-mounted engines. Underwater radiated noise emitted from the Z-peller was evaluated from cavitation noise tests using a water tank. In these tests, two types of Zpeller configurations were proposed, and the noise reduction effect was confirmed. Theresults are presented in this paper.

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The School of Engineering of Osaka University and the Department of electrical and electronic engineering, Nagoya Institute of Technology, coordinated and conducted survey for university students, students and teachers of high schools in order to realize effective activities of enlightenment for high school students. From the results of survey, it was suggested that the high-school teachers the most influential to high-school students. One of the promising contents in open lecture for high school students was the recent advanced technology allowing for the content of the science subjects in high school.

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When vessel's commanders receive assistance from tugboats on entering and leaving a berth, they use the agreed communication phrases, body language, hand gestures, and so on in each pilot district. In Japan, the agreed communication phrases named "The Settled Term of Maneuvering Orders for Towage Work" are defined by the Japan Harbor Tug Owners' Association. However, the results of the current state survey, which was executed by authors' group in 2010, showed that various kinds of "Non-standard" tug orders were actually used. The findings from the results also suggested that, when vessel's commanders used "Non-standard orders" including in the above-mentioned "The Settled Term," there were some gaps in perception between the vessel's commanders and the tugboat's commanders. These results reasonably lead to the conclusions that some definitely-agreed Maneuvering Orders are essential.

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　苫小牧港では港内擾乱時に

でフェリーを岸壁に押し付け，荷役機能を確保している．年間利用回数とPDO指数に有意な正の相関が認められたため，PDOとともにNPGO，AOの各指数と波浪の相関性等を調べた．対象期間は1980～2019年とした．その結果，①年最大波パワー値との有意な正の相関が1999年以前でAO指数，2000年以降でPDO指数について得られた．その要因として1980年当初のPDO指数とAO指数の強い負の相関関係が徐々に弱まってきていることが考えられる．②北海道周辺への台風の北上割合が増加し，100kW/m以上の年最大波パワー値出現率が2000年以降，それ以前の約2倍になった．③港内擾乱の年間発生率と年間利用回数は正の相関を示した．

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At present, there are few data on the characteristics of tow force and push force of tugboat in regular waves. In order to carry out the berthing maneuver correctly and safely, it is important to obtain the above data. In this paper, the characteristics of tow force and push force of tug boat in regular waves, relating to the change of wave length/ship length ratio, wave height, propeller thrust and so on, was studied through model experiments using a twin Azimuth-circle Drive Propeller (A. D. P.) tugboat model. Main results are as follows; (1) Mean tow force and mean push force in waves hardly changed comparing with each force in still water. (2) Fluctuating component of tow force and push force increased in approximate proportion to wave height. (3) The above fluctuating forces decreased inverse proportion to output of A. D. P

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The most important task of harbor tug boats are to support berthing / unberthing of vessels, because marine pilots use those tug boats for safe and efficient ship operation when assisting vessels’ berthing or unberthing. In Japan, the new pilotage low has been active since 2007 and included the third grade pilots which newly established. Unfortunately, they do not have enough experience of tug boat management. They are trying to study about tug boats handling in the harbor for large vessels using ship handling by navigation simulation systems. The senior pilots teach them how to use the tug boats in the ship handling simulator, too. However, the senior pilots have only the experience but do not have standard of the evaluation for management of tug boats handling. In this paper, the authors propose how to evaluate the tug boat handling for ship berthing using the new standard, which is named “Evaluation on elements for tug boat handling.” It is extracted from natural images of ship berthing at actual port named Yokohama. The new standards are consisted of three elements which are propelling power of tug boats, its direction and duration of power. We tried to compere the values of the three elements between actual ship handlings and ship handlings by the simulation, then confirmed their effects.

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