Nomogram for Velocities of Partial Flows in Sewers

Abstract

For the design of sewers nomograms are available in the literature for various flow equations. These nomograms can be used only for the condition when the depth of flow is full diameter of the sewer. The sewers are invariably designed to flow only for partial depths. For design of sewers involving determination of velocities and discharges under partial flow conditions another graph, depicting the relationship between ratios of depths of flow and ratios of discharge and velocity when flowing partially and those when flowing full, is required in conjunction with the above nomograms. The conventional method for solving a problem under partial flow conditions of a sewer involves six steps consisting of arithmetical calculations and reference to more than one chart or graph. The time and effort required for a designer are thus considerable. A nomogram is developed to eliminate all the tedious procedures involved in the conventional method. The required parameters can be directly read on the nomogram with reasonable accuracies for flows between 0.25 and 0.75 diameters.