Open Channel Hydraulics

Abstract

The study of open channel hydraulics is a challenging and exciting endeavor becai.rse of the influence of gravity on free surface flows. The position of the free surface is not known a priori, and counterintuitive phenomena can occur from the liewpoint of the first-time sludent of open channel flow. This book offers a study of gravity flows staning from a firm foundarion in modern fluid mechanics that includes both experimental results and numerical computation techniques. The development of the subject matter proceeds from basic fundamentals to selected applications with numerous worked-out examples. Experimental results and their comparison with theory are used throughout the book to develop an understanding of free-surface flow phenomena. Computational tools range from spreadsheets to computer programs to solve more difficult problems. Some computer programs afe provided in Vsual BASIC, both as leaming tools and as examples to encourage the use of computational methods regardless of the platform available in a very dynamic environment. In addition, several well-known computer packages available in the public domain are demonstrated and discussed to inform users with respect o lhe methodologies employed and their limitations. The basic equations ofcontinuity, energy, and momentum are derived for open cbannel flow in the first chapter, from the viewpoint of both a finite control volume and an infinitesimal control volume, although the complete derivation of the general unsteady form of the differential momentum equation is saved for Chapter 7. Dimensional analysis is introduced in some detail in the hrst chapter berause of its use throughout the book. This is followed by Chapters 2 and 3 on the specific energy concept and the momentum function. respectively, and their applications to open channel flow problems. Design of open channels for uniform flow is examined in Chapter 4 with a detailed consideration of the estimation of flow rcsistance. Applications include the design ofchannels with vegetative and rock riprap linings, and the design of storm and sanita4r sewers. Chapter 5, on gradually varied flow, emphasizes modem numerical solution techniques. The methodology for watersurface profile computation used in current computer prcgrams promulgated by federal agencies is discussed, and example problems are given. The design of hydraulic structures, including spillways, culverts, and bridges, is the subject of Chapter 6. Accepted computer programs used in such design are introduced and their methodologies thoroughly explored. Chapters 7, 8, and 9 develop cunent techniques for the solution of the one-dimensional Saint-Venant equations of unsteady flow and their simplifications. In Chapter 7, the Saint-Venant equations are derived, and the method of characteristics is introduced for the simple wave problem as a means of understanding the matbematical transformation of the governing equations into characteristic form. The numerical techniques of explicit and implicit finite differences and the numerical method of characteristics are given in Chapter 8, with applications to hydroelectric transients in headraces and tailrac