Showing posts with label Resistance of Ships. Show all posts
Showing posts with label Resistance of Ships. Show all posts

Saturday, December 12, 2009

The Wave Resistance of Ship By J.H. Michell

John Henry Michell (1863-1940) published scientific papers only between 1890
and 1902, but included in his 23 papers from that short but productive period are some of the most important contributions ever made by an Australian mathematician.
In this blog I shall concentrate on the extraordinary 1898 paper "The wave resistance of a ship," Phil. Mag.(5) 45, 106-123. There are many reasons why this paper was an astounding achievement, but perhaps the most remarkable is that the resulting formula has not been improved upon to this day. In the computer age, many efforts have been made to do so, but with little success so far. The formula itself involves a triple integral of an integrand constructed from the offset data for the ship's hull, and even the task of evaluating this triple integral is not a trivial one on today's computers; another reason for admiration of Michell's own heroic hand-calculated numerical work in the 1890's. Lack of a routine algorithm for Michell's integral has inhibited its use by naval architects and ship hydrodynamic laboratories, and there has been a tendency for it to receive a bad press based on unfair comparisons, e.g. comparison of model experiments (themselves often suspect) with inaccurate computations or computations for the wrong hull, etc. The original integral is in fact quite reasonable as an engineering tool, and some new results confirming this are shown. Improvement beyond Michell is however needed in some important speed ranges, and indications are given of recent approaches that may be promising.

I had searched for this paper everywhere, and luckily I found a website (a Russian one that too!) and I dont think it is available anywhere.
The Link is here.

Sunday, December 6, 2009

The Speed and Power of Ships: By D.W.Taylor

About the Book

In 1910,Admiral D.W. Taylor published his great work of Naval Architecture which would go on to become a classic in the field of Naval Architecture: "The Speed and Power of Ships," which has become internationally known to all Naval Architects as a standard book in the field of Resistance and Propulsion. In the preface Taylor sums up the purpose of this book in the following words: "The intention of this work is to treat in a consistent and connected manner, for the use of Naval Architects, the theory of resistance and propulsion of vessels and to give methods, rules and formulae which may be applied in practice by those who have to deal with such matters. The contents are based largely upon model experiments carried out in towing tanks, such as were initiated in England nearly half a century ago by Mr. William Froude and are now generally recognized as our most effective means of investigation in the
field of resistance and propulsion. At the same time care has been taken to point out the limitations of the model experiment method and the regions where it ceases to be a reliable guide." After an introductory chapter on hydrodynamics, pertinent to this subject, the book deals comprehensively with the problem of resistance to driving a ship through water, in all its aspects, with special regard to the use of small models. The results of the vast experimental work are expressed in a great number of diagrams, giving curves which represent the resistance of a series of models, derived from a parent form by variation of the principal characteristics such as beam-draught ratio, speed-length ratio, coefficients of fineness, etc. The third chapter is devoted to the difficult subject of propulsion, which is here treated in a most complete and masterly manner. It comprises the general theory of propeller action, the results of extensive series of experiments with small models, presented in numerous diagrams by curves, various special problems such as that of cavitation, and finally a full discussion of the strength and design of propeller blades. The last chapters deal with ship trials and their analysis, and with the important practical problem of powering of ships, that is, the calculation of the engine power required to drive a given ship at a certain speed.
Altogether the book is an outstanding classic in engineering literature. Taylor had the rare advantage of a brilliant mind and a natural talent for expressing himself in concise scientific language. He was never satisfied until he had reached perfection in exposition and he avoided always the pitfall of stating opinions that were not completely buttressed by facts. His talent for experimental work found the best possible opportunity for development and achievement, due to the fact that he had at his disposal and under his independent direction a well equipped experimental plant, shaped according to his own ideas and provided with an exceptionally able staff of his own selection and trained by himself. His master mind used this tool to full efficiency.

Here is the Link:
http://www.archive.org/download/speedpowerofship00tayluoft/speedpowerofship00tayluoft.pdf