A B C of Hydrodynamics

Download or read book A B C of Hydrodynamics written by R. De Villamil and published by CreateSpace. This book was released on 2013-11 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Title Page Inscription: "Next to being right in this world, the best of all things is to be clearly and definitely wrong, because you will come out somewhere. If you go buzzing about between right and wrong, vibrating and fluctuating, you come out nowhere; but if you are absolutely and thoroughly and persistently wrong, you must, some of these days, have the extreme good fortune of knocking your head against a fact, and that sets you all straight again." —Huxley * * * * * An excerpt from the PREFACE : This little book has no pretensions to being a treatise on hydrodynamics. It is, as its title implies, only intended as an introduction to the study of that subject. There is not very much that is new in it; some of the quotations are so old that they have been forgotten, and so will appear to the reader of the ordinary text-books as if they were new. What is, I fancy, original is the way in which the matter is arranged and the subject presented. Instead of treating of the movement of a "perfect liquid" and then informing the reader that ordinary liquids behave quite differently, I have endeavoured to show that perfect and imperfect (?) liquids follow exactly the same laws, and under similar conditions move in a similar manner. The difficulties are generally supposed to be very great. Sir John Herschel told us that "if there be one part of dynamic science more abstruse and unapproachable than another, it is the doctrine of propagation of motion in fluids, and especially in elastic fluids like the air, even where the amount and application of the original acting forces are known and calculable." These difficulties are, I think, very largely artificial ones. It is well to remember what Dubuat said more than a hundred years ago: "On risque souvent de se tromper, quand on applique aux fluides les lois du mouvement qui conviennent aux solides." I might even go further and say that, when thinking of liquids, what (to the untrained mind) appears "obvious" or "appeals to common sense " is very frequently wrong — more frequently, perhaps, than not. When the student has trained himself to "think in pressures" many difficulties will disappear.