labora03

labora03 - HONG KONG UNIVERSITY OF SCIENCE AND TECHNOLOGY...

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HONG KONG UNIVERSITY OF SCIENCE AND TECHNOLOGY Department of Civil Structural Engineering CIVL 252---Hydraulics Spring of 2002 Hydraulics Lab C: Varied Flow—Water Flow Profile, Velocity Profile TA:Joyce Zhang 1. Introduction The flow in an open channel is usually non-uniform because of many factors including (I)irregularities in cross-section, alignment, roughness and slope of natural channels, (ii) man-made obstructions such as dams, bridge piers and other hydraulic structures, and (iii) unsteadiness of flow caused by dynamic control structures and/or by time and spatial varying inputs and outputs such as runoff and infiltration. Even in the laboratory it is difficult, if not impossible, to produce a truly uniform flow because the length of the flume is often not sufficient to establish this flow regime. Unlike the uniform flow, the non-uniform flow varies with spatial positions in the open channel flow. The prediction of the flow profiles in the non-uniform channel flow is one of the most important aspects in the Engineering Hydraulics. If a non-uniform flow occurs over a relatively short distance, then the flow velocity and depth vary rapidly. That is, the rate of change of depth and velocity with distance is very large. This type of non-uniform flow is referred to as either “Hydraulic Jump (HJ)” or “ Rapidly Varied Flow (RVF)”. When the flow is a RVF, skin friction effects can frequently be neglected, and in many instances, solutions may be obtained by simultaneously considering the mass conservation law and the momentum equation. It must be stressed that momentum and energy are not equivalent concepts in RVF. Indeed, momentum is conserved but energy is not. On the other hand, if the flow varies gradually, skin friction resistance has a significant influence on the surface profiles. The quantitative description of the Gradually Varied Flow (GVF) requires the integration of either the equations of continuity and momentum or ocntinuity and energy. The fact that we can use the momentum or the energy implies equivalency of these two concepts for Gradually Varied Flow (GVF) problems. To be sure, most cases of non-uniform flow in open channels represent a combination of both RVF and GVF. The main objective of this experiment is to study both RVF and GVF and, in particular, to compare experimentally measured surface profiles with theoretically computed profiles. 2. Apparatus
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This note was uploaded on 03/19/2012 for the course CIVL 000 taught by Professor Kk during the Spring '10 term at HKUST.

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labora03 - HONG KONG UNIVERSITY OF SCIENCE AND TECHNOLOGY...

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