ABSTRACT
Lamont1 and others have shown that the same form of equation is applicable to other classes of pipe. The value of a may be obtained from tables or from pipe tests carried out at intervals of time. 5.10 Non-circular Pipes and Conduits In the case of a non-circular section (e.g. box culvert flowing full) it is unfortunately not possible to develop general expressions for the fric tion factor by the same sort of analytical reasoning as was adopted for circular pipes. This is because the velocity and shear stress gradients are no longer uniformly distributed about the pipe axis. Similar con siderations apply to open channel flow and, as explained in the latter connection (Ch. 7, Sect. 7.3.2), the substitution of the hydraulic radius R (sectional area -f-perimeter) for D/4 in the friction factor formulae is an artifice which is found to yield results that are of reasonable accuracy. But of course it is important that the degree of asymmetry should not be excessive.
