Hydraulic Flow Reviewed

Abstract

THE book is in two parts, the first of which deals with the flow of water in pipes and channels. The author had occasion to investigate certain conditions of flow in the Thirlmere aqueduct, which supplies water to Manchester, and, finding the variation in the coefficients of accepted formulas unsatisfactory, he was led to review the whole subject of the laws of flow, with the result that he has devised a series of formulæ in which the coefficient is independent of variations in the size or gradient of the conduit. Taking the equations of five well-known experimentalists, which he styles “the more salient formulæ” on the subject, he shows that they are of the form = Km^½i^½. He then points out that the square root indices of m (the hydraulic mean depth) and of i (sine of slope) are incompatible with a constant value for the coefficient k, for a particulaf class of pipe or channel. In accordance with the precedent set by Hagen and followed by Thrupp and others, he recommends the adoption of the more general expression v= Km_αi_β, and from the analysis of a considerable number of published data he is enabled to assign a series of values to K, α, and β which give consistent and satisfactory results when applied to a wide range of cases. The formulæ thus obtained are sixteen in number, of which we only quote the first as typical of the rest. For new asphalted cast-iron pipes the value is v= I74·1m⁷⁶⁹i⁵²⁹. The results are plotted in diagrammatic form for reference, and the advantages of using a system of logarithmic co-ordinates (which give straight-line diagrams) for this purpose are pointed out.

Hydraulic Flow Reviewed.

By A. A. Barnes. Pp. xi + 158. (London: E. and F. N. Spon, Ltd., 1916.) Price 12s. 6d. net.