Book•
Open channel flow
01 Jan 1966-Iss: 1
TL;DR: The importance of basic principles is recognized in this article in two ways : first, by devoting the opening chapters to a fairly leisurely discussion of introductory principles, including a recapitulation of the underlying arguments derived from the parent subject of fluid mechanics; and second, by takingnevery opportunity in the later chapters to refer back to this earlier material in order to clarify particular applications as they arise.
Abstract: PrefaceAlthough this book was originally conceived as a text for use by the civilnengineering student in advanced courses either in his senior year or at graduatenlevel, it is also designed to have some appeal to the practicing engineer.Open channel flow, like any topic of engineering interest, is defined andnclassified partly by its possession of certain characteristic applications andnpartly by the principles that are invoked to deal with them. This particularnsubject is so rich in the variety and interest of its practical problems that anyntextbook on the subject is in danger of becoming a mere catalogue of applicationsnand routine techniques devised for dealing with them. But it has to benremembered that mastery of this subject, as of any other, demands a grasp ofbasic principles no less than a facility in routine operations. The practicing nengineer is reminded of this fact whenever he turns from the familiar numericsnof backwater curves and flood-routing procedures to some unusual transitionnproblem whose solution requires a good grasp of fundamentals.The importance of basic principles is recognized in this text in two ways :nfirst, by devoting the opening chapters to a fairly leisurely discussion of introductorynprinciples, including a recapitulation of the underlying argumentsnderived from the parent subject of fluid mechanics; and second, by takingnevery opportunity in the later chapters to refer back to this earlier materialnin order to clarify particular applications as they arise. It is hoped that thenpracticing engineer, as well as the student, will find this kind of treatmentnhelpful, and a compensation for the fact that not every application is pursuednthrough every possible variant that occurs in practice. Further compensationnwill, it is also hoped, be found in the fairly complete system of references andnin the unusually large number of applied topics dealt with.This insistence on the importance of principles does not imply that theynshould be given a status and significance independent of the applications theynpossess. The engineer invokes principles in order to deal with problems thatnarise in practice, and when dealing with these general principles he stillnremains in touch with the physical events which have prompted the need to generalize. This notion has dictated the structure of many chapters in thisnbook, particularly Chapters 2 and 3. In each of these, a typical basic problemnis discussed first; the theory is then developed to solve this problem, and isnfinally generalized to cover other problems as well. n n n n
Citations
More filters
TL;DR: In this paper, a simple model that satisfies most of these criteria uses depth-averaged equations of motion patterned after those of the Savage-Hutter theory for gravity-driven flow of dry granular masses but generalized to include the effects of viscous pore fluid with varying pressure.
Abstract: Recent advances in theory and experimen- tation motivate a thorough reassessment of the physics of debris flows. Analyses of flows of dry, granular solids and solid-fluid mixtures provide a foundation for a com- prehensive debris flow theory, and experiments provide data that reveal the strengths and limitations of theoret- ical models. Both debris flow materials and dry granular materials can sustain shear stresses while remaining stat- ic; both can deform in a slow, tranquil mode character- ized by enduring, frictional grain contacts; and both can flow in a more rapid, agitated mode characterized by brief, inelastic grain collisions. In debris flows, however, pore fluid that is highly viscous and nearly incompress- ible, composed of water with suspended silt and clay, can strongly mediate intergranular friction and collisions. Grain friction, grain collisions, and viscous fluid flow may transfer significant momentum simultaneously. Both the vibrational kinetic energy of solid grains (mea- sured by a quantity termed the granular temperature) and the pressure of the intervening pore fluid facilitate motion of grains past one another, thereby enhancing debris flow mobility. Granular temperature arises from conversion of flow translational energy to grain vibra- tional energy, a process that depends on shear rates, grain properties, boundary conditions, and the ambient fluid viscosity and pressure. Pore fluid pressures that exceed static equilibrium pressures result from local or global debris contraction. Like larger, natural debris flows, experimental debris flows of ;10 m 3 of poorly sorted, water-saturated sediment invariably move as an unsteady surge or series of surges. Measurements at the base of experimental flows show that coarse-grained surge fronts have little or no pore fluid pressure. In contrast, finer-grained, thoroughly saturated debris be- hind surge fronts is nearly liquefied by high pore pres- sure, which persists owing to the great compressibility and moderate permeability of the debris. Realistic mod- els of debris flows therefore require equations that sim- ulate inertial motion of surges in which high-resistance fronts dominated by solid forces impede the motion of low-resistance tails more strongly influenced by fluid forces. Furthermore, because debris flows characteristi- cally originate as nearly rigid sediment masses, trans- form at least partly to liquefied flows, and then trans- form again to nearly rigid deposits, acceptable models must simulate an evolution of material behavior without invoking preternatural changes in material properties. A simple model that satisfies most of these criteria uses depth-averaged equations of motion patterned after those of the Savage-Hutter theory for gravity-driven flow of dry granular masses but generalized to include the effects of viscous pore fluid with varying pressure. These equations can describe a spectrum of debris flow behav- iors intermediate between those of wet rock avalanches and sediment-laden water floods. With appropriate pore pressure distributions the equations yield numerical so- lutions that successfully predict unsteady, nonuniform motion of experimental debris flows.
2,426 citations
01 Jan 1989
TL;DR: In this paper, a procedure for the determination of Manning's roughness coefficient (n) for channels and flood plains analyzes the different roughness factors that affect the roughness coefficients.
Abstract: Although much research has been done on Manning's roughness coefficients for stream channels, very little has been done on the selection of roughness values for densely vegetated flood plains. A procedure for the determination of Manning's roughness coefficient (n) for channels and flood plains analyzes the different roughness factors that affect the roughness coefficients for channels and flood plains. By determining the value of each factor and combining those values, the n value can be determined. Another procedure deals with densely vegetated flood plains where the major roughness is caused by trees, vines, and brush. The n value for this type of flood plain can be determined by measuring the "vegetation density" of the flood plain. Photographs of flood plain segments where n values have been verified are presented as a comparison standard to aid in assigning n values to similar flood plains. (FHWA)
992 citations
Cites background from "Open channel flow"
...Suggested values for Manning's n, tabulated according to factors that affect roughness, are found in references such as Chow (1959), Henderson (1966), and Streeter (1971)....
[...]
TL;DR: In this article, a transient storage model was used to simulate solute transport in a very small (0.0125 m3s−1) mountain pool-and-riffle stream.
Abstract: The physical characteristics of mountain streams differ from the uniform and conceptually well- defined open channels for which the analysis of solute transport has been oriented in the past and is now well understood. These physical conditions significantly influence solute transport behavior, as demonstrated by a transient storage model simulation of solute transport in a very small (0.0125 m3s−1) mountain pool-and-riffle stream. The application is to a carefully controlled and intensively monitored chloride injection experiment. The data from the experiment are not explained by the standard convection-dispersion mechanisms alone. A transient storage model, which couples dead zones with the one-dimensional convection-dispersion equation, simulates the general characteristics of the solute transport behavior and a set of simulation parameters were determined that yield an adequate fit to the data. However, considerable uncertainty remains in determining physically realistic values of these parameters. The values of the simulation parameters used are compared to values used by other authors for other streams. The comparison supports, at least qualitatively, the determined parameter values.
795 citations
TL;DR: In this article, a new variational framework for various existing Smooth Particle Hydrodynamic (SPH) techniques and a new corrected SPH formulation are presented, where the linear and angular momentum preserving properties of SPH formulations are also discussed.
708 citations
TL;DR: In this paper, an overview is given of empirical relationships that can be used to estimate the most important parameters of debris-flow behavior, including peak discharge, the mean flow velocity, the total travel distance, and the runout distance on the fan.
Abstract: The assessment of the debris flow hazard potential has to rely on semi-quantitative methods. Due to the complexity of the debris-flow process, numerical simulation models of debris flows are still limited with regard to practical applications. Thus, an overview is given of empirical relationships that can be used to estimate the most important parameters of debris-flow behavior. In a possible procedure, an assessment of a maximum debris-flow volume may be followed by estimates of the peak discharge, the mean flow velocity, the total travel distance, and the runout distance on the fan. The applicability of several empirical equations is compared with available field and laboratory data, and scaling considerations are used to discuss the variability of the parameters over a large range of values. Some recommendations are made with regard to the application of the presented relationships by practicing engineers, apart from advocating field reconnaissance and searching for historic events wherever possible.
662 citations
Additional excerpts
...For Froude scaling (e.g., Henderson 1966) we have to satisfy the relationships: Q∗ = Qp2/Qp1 ∼ λ5/2∗ , (A1) M∗ = M2/M1 ∼ λ3∗....
[...]