Proceedings of the American Society of Civil Engineers Volume 22 (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. 1896 Excerpt: ...of open-topped tubes extending upward from the pipe, coincides with the hydraulic grade A of a straight line from the upper to the lower end of a pipe is true only when the inner surface opposes a frictional resistance which is uniform throughout the whole length of the pipe. In such cases the coincidence of the grade lines depends solely on the uniformity and not on the amount of the frictional resistance. The discharge depends on the amount of the friction, and is proportioned to coefficients of discharge determined experimentally and corresponding to the roughness n in the Knit rr formula. According to the principles of the Kutter formula the coefficient c is independent of the slope in the equation v = c /rh, when r is greater than 0.1 ft. and h is greater than 1 ft. in 1000 ft. According to experiments on the flow of water through pipes the variation of the coefficient is greater, but the difference may be due, in part at least, to the use of the term in a sense not warranted by the conditions of flow in open channels. In the case of an open channel with a constant discharge and with irregular cross-sections or a variable roughness of the sides and bottom, the velocity and volume of the water vary in accordance with the slopes and the resistances to the flow in different sections of the channel, and an obstruction placed in one section does not diminish the discharge or appreciably affect the velocity or volume of the flow in other sections, except for a short distance above or below the obstruction. In the case of a full pipe there can be no difference in the velocity or sectional area of the water, and an obstruction to the flow at any one point is followed by a change in the pressure against the inner surface at all points, which would affect the pi...