船舶與海洋工程畢業(yè)設計外文翻譯--常規(guī)貨船的橫搖阻尼在池田方法基礎上的一個簡單預測方法及其局限性-在線瀏覽
2024-07-23 18:35本頁面
【正文】 (kgfm)/roll angular velocity (rad/sec)) can be expressed as follows: B44 Bbk (1) At zero forward speed, each ponent except the friction and lift ponents are predicted for each cross section with unit length and the predicted values are summed up along the ship length. The friction ponent is predicted by Kato’s formula for a threedimensional ship shape. Modification functions for predicting the forward speed effects on the roll damping ponents are developed for the friction, wave and eddy ponents. The puter program of the method was published, and the method has been widely used. For these 30 years, the original Ikeda’s method developed for conventional cargo ships has been improved to apply many kinds of ships, for examples, more slender and round ships, fishing boats, barges, ships with skegs and so on. The original method is also widely used. However, sometimes, different conclusions of roll motions were derived even though the same Ikeda’s method was used in the calculations. Then, to check the accuracy of the puter programs of the same Ikeda’s method, a more simple prediction method with the almost same accuracy as the Ikeda’s original one has been expected to be developed. It is said that in design stages of ships, Ikeda’s method is too plicated to use. To meet these needs, a simple roll damping prediction method was deduced by using regression analysis [8]. Previous Prediction Formula The simple prediction formula proposed in previous paper can not be used for modem ships that have high position of center of gravity or long natural roll period such as large passenger ships with relatively flat hull shape. In order to investigate its limitation, the authors pared the result of this prediction method with original Ikeda’s one while out of its calculating limitation. Fig. 1 shows the result of the parison with their method of roll damping. The upper one is on the condition that the center of gravity is low and the lower one on the condition that the center of gravity is high. From this figure, the roll damping estimated by this prediction formula is in good agreement with the roll damping calculated by the Ikeda’s method for low position of center of gravity, but the error margin grows for the high position of center of gravity. The results suggest that the previous prediction formula is necessary to be revised. Methodical Series Ships Modified prediction formula will be developed on the basis of the predicted results by Ikeda’s method using the methodical series ships. This series ships are constructed based on the Taylor Standard Series and its hull shapes are methodically changed by changing length, beam, draft, midship sectional coefficient and longitudinal prismatic coefficient. The geometries of the series ships are given by the following equations. Proposal of New Prediction Method of Roll Damping In this chapter, the characteristics of each ponent of the roll damping, the frictional, the wave, the eddy and the bilge keel ponents at zero advanced speed, are discussed, and a simple prediction formula of each ponent is well known, the wave ponent of the roll damping fo
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