Hydraulics, Volume 2 (Google eBook)

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Longmans, Green, and Company, 1908 - Hydraulics
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Page 168 - Change of motion is proportional to the impressed force and takes place in the direction of the straight line in which the force acts.
Page 163 - The residual resistance varies as the square of the speed up to 11 knots; as the cube, at 12 to 13 knots; as the fourth power, about 14 knots; and at a higher rate than the fifth power at 18 knots. Then the index begins to fall, reaching the square at 24 knots, and falling still lower at higher speeds. It will be seen, therefore, that when this small vessel has been driven up to...
Page 164 - ... which the resistance is varying as the highest power of the speed. These are suggestive facts. Frictional resistance, as is well known, is a most important matter in all classes of ships and at all speeds. Even in the typical destroyer this is so. At 12 knots the friction, with clean-painted bottom, represents 80 per cent of the total resistance; at 16 knots, 70 per cent; at 20 knots, a little less than 50 per cent; and at 30 knots, 45 per cent. If the coefficient of friction were doubled, and...
Page 150 - Esq., one of the proprietors of the works, took fright and ran off dragging the boat with it, and it was then observed, to Mr. Houston's astonishment, that the foaming stern surge which used to devastate the banks had ceased, and the vessel was carried on through water comparatively smooth with a resistance very greatly diminished.
Page 144 - ... to 22 knots. The figures are interesting, however, as illustrations of the principle that economy of propulsion is favored by increase in dimensions as speeds are raised. Going a step further, it may be assumed that in unsheathed cruisers of this class about 40 per cent, of the displacement will be required for the hull and fittings, so that the balance, or " disposable weight," would be about 60 per cent.; say 6600 tons for the smaller vessel and 8500 tons for the larger, a gain of nearly 2000...
Page 65 - It has often been noticed that when an isolated group of waves, of sensibly the same length, is advancing over relatively deep water, the velocity of the group as a whole is less than that of the individual waves composing it. If attention be fixed on a particular wave, it is seen to advance through the group, gradually dying out as it approaches the front...
Page 145 - Taking a 3O-knot destroyer, for example, the speed trials are made with a load not exceeding 12 to 14 per cent of the displacement. In a swift cruiser the corresponding load would be from 40 to 45 per cent, or proportionately more than three times as great. What this difference means may be illustrated by two statements. If the load were trebled, and the...
Page 65 - If attention be fixed on a particular wave, it is seen to advance through the group, gradually dying out as it approaches the front, whilst its former place in the group is occupied in succession by other waves which have come forward from the rear...
Page 241 - When the speed was still further increased, the screw, as a whole, revolved in a cylindrical cavity, from one end of which the blades scraped off layers of solid water, delivering them on to the other. In this extreme case nearly the whole energy of the screw was expended in maintaining this vacuous space.
Page 41 - ... the column to each other ; these are all the forces and the motions concerned in the matter. The motive power thus stored during the anterior half of the wave is restored in the latter half wave length thus : the column raised to its greatest height presses on both its posterior and anterior surface, on the anterior surface it presses forward the anterior column, tending to sustain its velocity and maintain its height ; on the posterior column its pressure tends to oppose the progress and retard...

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