単螺旋船に於ける船尾振動の発生機構に依る分類とその防止法に就いて

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Regarding the problem of vibration at the stern of single screw vessels, active research is recently in progress in many of the countries and several treatises have been made public in which the problem has been touched upon.For example, the followings may be mentioned : On vibration at the stern studied by Baier (S.N.A.M.E.1952)Vibration at the stern as referred to in the treatise on vibration re Gopher Mariner by Mc Goldrisk (S.N.A.M.E.1955)Vibration at the stern as referred to in the treatise on research of hull vibration by Ramsay(T.I.N.A.1956)Vibration at the stern as referred to in the treatise on research of hull vibration by Kumai(I.S.P. Vol.4,No.32,1957)The Writer stated in the "International Shipbuilding Progress, Vol.2,No.10,1955" certain fundamental theories on vibration at the stern under the title of-"A Contribution to the Vibration at the Stern of Single Screw Vessels", and these theories are herebelow further developed more extensively.The principal outcome of the research is : -Upon detailed analysis of the vibrations which are collectively called in the terms of "vibration at the stern", it was found that those vibrations are caused by different causes, and can be classified as follows : Forced type stern vibration Resonance type stern vibraiton Associated type stern vibration Apparent stern vibration The forced type stern vibration takes place on ordinary vessels where the hull vibration is concentrated to aaprox. aft 1/4 L of the hull, and this phenomenon is conspicuous in large-type vessels. The cause for this vibration is a superposition of forced vibration of higher mode.The resonance type stern vibration takes place in cases where the hulls are equipped with coupled oscillatory system composed of engines, boilers, unsuported deck, etc.The "zone of vibration at the stern" is determined by the co-relation between the distribution condition of natural frequency of the hull and the blade frequency of out-of-balance force caused by propeller, and if the resonance frequency of the whole system, including the coupled oscillatory system, is within the zone and also if the blade frequency coincides with it, there occurs an extremely violent vibration at the stern in resonance condition. Such is called reonance type stern vibration.In regard to the associated type of stern vibration, the mode of vibration will be of interest, however, from purely vibrational point of view, it is rather out of question because none of this type of vibration is violent. This type of vibration is created by an interference between the exciting force of the propeller and the reaction of coupled oscillatory system, the two forces simultaneously acting upon the hull.Regarding apparent stern vibration, it is sometimes called "stern vibration", because of the fact that, when hull vibration occurs, the amplitude of vibration is liable to appear in large amount in the vicinities of both forward and aft ends of the vessel due to the strength of hull scantling being smaller at forward and aft than at the midship portion of the vessel.However, the Writer would like to distinguish this type of vibration from the other three types, and give thereto an appellation of "apparent stern vibration".The reason is that this type of vibration substantially differs from the other three types, and besides, the distribution of the vibration along the hull does not form stern vibration in a true sense of the term.Lastly, the Writer will describe as to the principle of preventing the vibration of the hull, for the purpose of giving an example of practical appliance of this research.Theoretically, the outcome of this research can be applied for preventing not simply the stern vibration but also hull vibration to be caused by any force which will act upon the hull. Of course, it can be utilized effectively for preventing the stern vibration which is being taken up as a problem to be solved.Regarding the theory on the principle for preventing hull vibration, it
社団法人日本船舶海洋工学会の論文

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播磨造船所研究部

単螺旋船に於ける船尾振動の発生機構に依る分類とその防止法に就いて

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