Numerical Investigation of Flow in Triangular Gutters

Abstract Focusing on triangular gutters with one vertical side, four issues pertaining to the design of street gutters are addressed: (1) the proper coefficient in Manning's formula for uniform flow and friction loss in gutters; (2) adjustment of frictional resistance for spatial inflow; (3) whether uniform flow occurs in gutters with spatially increasing flow; and (4) interaction with inlets. The first of these issues is addressed by considering historical and modern information to recommend the best of two different equations that have been put forward for determining the uniform flow capacity and friction loss in gutters. The second concern is addressed for subcritical and supercritical gutter flow, for which practical, generalized numerical solutions are derived. The range of parameters for which uniform flow provides an adequate approximation is demonstrated theoretically and by example. Among the important conclusions is that the common practice of using Manning's equation alone for such problems is not always adequate. Practical recommendations are made to address the third issue. The fourth concern is addressed by building on the material thus presented and literature information. This work has important implications for more generally regarding the characteristics and relationships for subcritical and supercritical flow in open channels.