Towards a Problem-Oriented Library for the Computer Analysis of Stratified Flow Phenomena

Abstract

<p> Flows in channels or estuaries may exhibit variations in density arising· from differences in temperature, salinity or suspended solids. In the absence of significant vertical mixing, stable, discrete layers may form with distinct density interfaces. </p> <p> This thesis presents a computational approach for the analysis of two-layer, vertically stratified, one-dimensional horizontal flows in open channels. A variety of such problems are identified and a critical survey of the existing literature is presented. A framework is defined against which these problems are classified and decomposed into analytical problems of the simplest possible scope. Based on the conditions that lead to changes in flow characteristics, four research areas are examined. These are energy balance, interfacial hydraulic jump, lock exchange flows, and long transitions. Although restricted to essentially one-dimensional flows, the analytical study of these four areas is extended to allow for non-uniform velocity distribution the introduction of boundary-layer displacement thicknesses and correction factors for kinetic energy and momentum. Also, a significant feature of the study is the ability to handle channels of arbitrary cross-sectional geometry. </p> <p> The basic philosophy of the approach followed in this study is to develop a relatively simple and computationally econaoical procedure which is applicable to a wide variety of problems involving channels systems of arbitrary geometry and boundary conditions. A library of computer subroutines provides a convenient means of developing an open-ended system of computational techniques for the solution of a wide range of problems. Such a library of computational algorithms may also promote. cooperation and collaboration among researchers and engineers concerned with stratified flow hydraulics. Such algorithms should provide solutions for frequently recurring problems, should be mutually compatible and allow the construction of relatively complex analytical models in a modular fashion. A comprehensive library of routines is developed which consists of fourty-four subroutines and functions. This evolves as a well-defined hierarchy of algorithms in which the most basic algorithms are nested within the more sophisticated ones to the sixth or seventh level. </p> <p> The computational algorithms are tested for theoretical and computational performance. Numerical predictions are compared with available experimental and field data. Moreover, an experimental program is described which is designed and carried ·out to verify the numerical predictions obtained for the first of the above-mentioned four topics. </p> <p> An important aspect of the study is the illustration of the application of the routines in the solution of typical practical problems such as selective withdrawal from stratified water bodies and recirculation of cooling water from power plants. In addition, to facilitate utilization of the programs by others, complete documentation and listings are provided. </p>