Search

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...

Collection conduits flowing full with nonuniform inflow (variable rate of increase in flow with distance along the conduit length) include well screens (vertical and directionally drilled); submerged effluent collectors; and certain types of inboard weir configurations for settling tanks. Certain subsurface drains used in environmental engineering applications and civil engineering more generally may be inadvertently designed for full-flowing conditions. Formulation of the problem for such collection conduits is presented in terms of the applicable differential equation, slope invariance, the frictionless solution for a general cross section, a uniform-inflow solution, and the difference formulation. The importance of checking inflow uniformity is discussed and exemplified. Dimensional analysis is then employed to demonstrate the relationship between variables, leading to a new generalized numerical solution. That solution is presented in a graphical form which provides further useful display of the relationships between variables and quantitative information for design and analysis. The detrimental effects of flowing-full conditions in subsurface drains is demonstrated, and it is noted that existing design methods may unintentionally cause such conditions to occur.

A theory presented previously by the writer explained the asymmetric flow patterns occurring in symmetric rectangular expansions with subcritical flow. The theory is extended in the present paper to supercritical flows, in which the hydraulic jump is one of the flow features. The theory is shown to agree with available observations. Transverse oscillatory conditions are discussed in terms of a dynamic instability that can accompany static stability. The ranges for which experimental data are available with which to test the theory are identified, making it apparent where additional data would be useful for the full range of the problem. The phenomenological understanding provided by the present paper is important to the development of stabilization measures. In addition to stabilization by submergence, the hydraulic jump should be amenable to stabilization by other referenced methods, including various vane configurations and pipe communication between the eddy regions.

Building upon a companion paper, the present paper addresses additional mechanisms of the tidal bore, including channel taper and friction; building, maximum height, variation, and dissipation of the bore; and standing waves. Early studies of these mechanisms are cited and discussed in historical context. Relationships developed to investigate the effects of horizontal channel taper, vertical channel taper, and channel friction agree qualitatively with and explain field observations. Building of the bore is explained, with favorable comparison of methodology with flume observations. The maximum height that the bore is capable of achieving is one of its most interesting features; this is explained in terms agreeing with experimental observation. The two forms of the jump, undular and wall-like, are discussed. The variation of the bore height as it moves into regions of greater or lesser depth is described from field observations and flume observation, and relationships derived which explain such variation. Frictional dissipation of the bore is discussed. Standing waves that occur after the tidal bore has passed are explained as a separate phenomenon.Copyright © 2012 by ASME

Asymmetric flow patterns may occur in perfectly symmetric abrupt expansions, in which the main flow deflects and attaches arbitrarily to one wall of the expansion. With the notable exception of “fluidic” devices, asymmetric flow patterns are detrimental in most civil engineering applications. The adverse effects include lengthening of the distance to full-width flow in expansions, inefficient operation of screens in screen channels, and increasing the potential for vortexing in pump intakes. No good explanation or prediction of the onset of asymmetric flow patterns is known to exist. This paper attributes the asymmetric behavior to a static instability of the system occurring under certain conditions of expansion geometry. The stability is investigated by analyzing the forces acting on the system when it undergoes a small deflection from its symmetric position. A mathematical stability criterion is developed and applied to subcritical, horizontal, rectangular expansions. The results are in excellent agreement with experimental observations (limited to small Froude Numbers). The predictive method is extended theoretically to the analysis of certain preventive and corrective measures. Means of extending the analyses to more complex two-dimensional and three-dimensional configurations are examined.