Open AccessShip waves: their variation with certain systematic changes of form
Publication year - 1932
Publication title -
proceedings of the royal society of london. series a, containing papers of a mathematical and physical character
Language(s) - English
Resource type - Journals
eISSN - 2053-9150
pISSN - 0950-1207
DOI - 10.1098/rspa.1932.0095
Subject(s) - stern , smoothing , interference (communication) , elevation (ballistics) , point (geometry) , simple (philosophy) , mathematics , geology , mechanics , mathematical analysis , geometry , computer science , physics , marine engineering , engineering , statistics , telecommunications , channel (broadcasting) , philosophy , epistemology
1. The following paper is an examination, by analysis and by curves, of a single definite problem in wave profiles. Consider a ship model, of great draught, in which at some point in the form, at bow, stern or shoulders, for example, there is a sharp corner giving a sudden change of slope of the horizontal lines of the model. What is the effect on the wave profile of replacing this sudden change by a gradual change of slope of the same total amount, but distributed uniformly over any given length of the ship’s form ? Apart from direct applications, the problem is suggested by certain other considerations. In comparing theoretical and experimental resistance curves, I suggested some years ago an indirect effect of the friction belt along the sides of the ship in that it may be equivalent to smoothing out the lines of the model, especially towards the stern. From an examination of interference effects with experimental models, it has been estimated that the effective length of the model is roughly 8 per cent, greater than the actual length, and this may probably be ascribed to some such frictional effect. The present paper deals with wave profiles since measurements of surface elevation are now becoming available, though the main results so far are for a simple model with straight lines and sharp corners; such a form simplifies the calculations but no doubt introduces other complications in practice, and a small correction for the smoothing effect of a friction belt would not be likely to account for the remaining differences between calculation and observation. It must be noted, moreover, that there are other approximations in the theory, apart from the neglect of fluid friction, but these need not be discussed here. For these reasons no attempt has been made to apply the results of the present paper directly to experimental data, but it is hoped that the progressive series of curves will be of interest in showing the changes in profile due to successive changes of form of a definite kind.