A Treatise on Hydraulics (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 Excerpt: ...In short supply pipes to turbines, velocities of 7 to 10 feet per second are not unusual. The reason for adopting somewhat lower velocities in small mains is that otherwise the rate of fall of pressure would be excessive. 85. Steady flow in pipes of uniform diameter.--If a long pipe connects two reservoirs at different levels, water will flow from the upper to the lower, and the conditions being constant the velocity and rate of discharge will be constant also. Steady flow being established, since the water starts from rest and comes back to rest, the work of gravity on the descending water is exactly balanced by the work of the resistances, of which much the largest is fluid frictionLet Q be the discharge in cubic feet per second, fl the cross section and d the diameter of the pipe, v the mean forward velocity of the water. Q = Slv = j dh cubic feet per second. (5). As the same quantity of water passes every section in unit time the velocity must be the same, that is if we understand by v the mean velocity of translation along the pipe. In fact, the velocity is greater at the centre of the cross section and less towards the sides of the pipe, and on this general condition eddying motions are superposed. But the mean velocity along the pipe is constant, and for simplicity the complications must be disregarded. The Chezy formula for flow in pipes.--A very simple theory furnishes an approximate formula which has been of very great service in hydraulics, and which with tabulated values of experimental coefficients is still employed more generally than any other in hydraulic calculations. Let Fig. 85 represent a short portion of a long pipe through which water is steadily flowing. The water enters and leaves at the same velocity, and consequently the work of ex...