ABSTRACT
All the relationships presented in Chapter 6 apply directly to circular pipe. However, many of these results can also, with appropriate modification, be applied to conduits with noncircular cross sections. I t should be recalled that the derivation of the momentum equation for uniform flow in a tube [e.g., Eq. (5-44)] involved no assumption about the shape of the tube cross section. The result is that the friction loss is a function of a geometric parameter called the "hydraulic diameter":
A Dh =4-(7-1)
WP where Ais the area of the flow cross section and WP is the wetted perimeter (i.e., the length of contact between the fluid and the solid boundary in the flow cross section). For a full circular pipe, Dh =D(the pipe diameter). The hydraulic diameter is the key characteristic geometric parameter for a conduit with any cross-sectional shape.
