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Fluids Discharge Measurement Structures and Systems

Civil Engineering and Design
Fluids Flow Design and Engineering
Hydraulics Design and Engineering

Fluids Discharge Measurement Structures and Systems
Basic Principles of Fluid Flow as Applied to Measuring Systems
400 Pages
Third Edition
M.G. Bos

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This book presents instructions, standards, and procedures for the selection, design, and use of structures, which measure or regulate the flow rate in open channels. It is intended to serve as a guide to good practice for engineers concerned with the design and operation of such structures. It is hoped that the book will serve this purpose in three ways: (i) by giving the hydraulic theory related to discharge measurement structures; (ii) by indicating the major demands made upon the structures; and (iii) by providing specialized and technical knowledge on the more common types of structures now being used throughout the world.

The text is addressed to the designer and operator of the structure and gives the hydraulic dimensions of the structure. Construction methods are only given if they influence the hydraulic performance of the structure. Otherwise, no methods of construction nor specifications of materials are given since they vary greatly from country to country and their selection will be influenced by such factors as the availability of materials, the quality of workmanship, and by the number of structures that need to be built.

The efficient management of water supplies, particularly in the arid regions of the world, is becoming more and more important as the demand for water grows even greater with the world’s increasing population and as new sources of water become harder to find. Water resources are one of our most vital commodities and they must be conserved by reducing the amounts of water lost through inefficient management. An essential part of water conservation is the accurate measurement and regulation of discharges.

TOC

BASIC PRINCIPLES OF FLUID FLOW AS APPLIED TO MEASURING STRUCTURES 17
General
Continuity
Equation of motion in the s-direction
Piezometric gradient in the n-direction
Hydrostatic pressure distribution in the m-direction
The total energy head of an open channel cross-section
Recapitulation
Specific energy
The broad-crested weir
Broad-crested weir with rectangular control section
Broad-crested weir with parabolic control section
Broad-crested weir with triangular control section
Broad-crested weir with truncated triangular control section
Broad-crested weir with trapezoidal control section
Broad-crested weir with circular control section
Short-crested weir
Critical depth flumes
Orifices
Sharpcrested weirs
Sharp-crested weir with rectangular control section
Sharp-crested weir with parabolic control section
Sharp-crested weir with triangular control section
Sharp-crested weir with truncated triangular control section
Sharp-crested weir with trapezoidal control section
Sharp-crested weir with circular control section
Sharp-crested proportional weir
The aeration demand of weirs
Estimating the modular limit for long-throated flumes
Theory
Energy losses upstream of the control section
Friction losses downstream of the control section
Losses due to turbulence in the zone of deceleration
Total energy loss requirement
Procedure to estimate the modular limit
Modular limit of short-crested weirs
Selected list of literature

AUXILIARY EQUIPMENT FOR MEASURING STRUCTURES
Introduction
Head measurement station
The approach channel
Tailwater level
Staff gauge
Stilling well
Maximum stage gauge
Recording gauge
The float-tape and the diameter of the float
Instrument shelter
Protection against freezing
Differential head meters
Selected list of references

THE SELECTION OF STRUCTURES
Introduction
Demands made upon a structure
Function of the structure
Required fall of energy head to obtain modular flow
Range of discharges to be measured
Sensitivity
Flexibility
Sediment discharge capability
Passing of floating and suspended debris
Undesirable change in discharge
Minimum water level in upstream channel
Required accuracy of measurement
Standardization of structures in an area
Properties and limits of application of structures
General
Tabulation of data
Selecting the structure
Selected list of references

BROAD-CRESTED WEIRS
Horizontal broad-crested weir
Descrip tion
Evaluation of discharge
Modular limit
Limits of application
The Romijn movable measuring/regulating weir
Description
Evaluation of discharge
Modular limit
Commonly used weir dimensions
Limits of application
Triangular broad-crested weir
Description
Evaluation of discharge
Modular limit
Limits of application
Broad-crested rectangular profile weir
Description
Evaluation of discharge
Limits of application
Faiyum weir
Description
Modular limit
Evaluation of discharge
Limits of application
Selected list of references

SHARP-CRESTED WEIRS
Rectangular sharp-crested weirs
Description
Evaluation of discharge
Limits of application
V-notch sharp-crested weirs
Description
Evaluation of discharge
Limits of application
Rating tables
Cipoletti weir
Description
Evaluation of discharge
Limits of application
Circular weir
Description
Determination of discharge
Limits of application
Proportional weir
Description
Evaluation of discharge
Limits of application
Selected list of references

SHORT-CRESTED WEIRS
Weir sill with rectangular control section
Description
Evaluation of discharge
Limits of application
V-notch weir sill
Description
Evaluation of discharge
Limits of application
Triangular profile two-dimensional weir
Description
Evaluation of discharge
Modular limit
Limits of application
Triangular profile flat-Vee weir
Description
Evaluation of discharge
Modular limit and non-modular discharge
Limits of application
Butcher’s movable standing wave weir
Description
Evaluation of discharge
Limits of application
WES-Standard spillway
Description
Evaluation of discharge
Limits of application
Cylindrical crested weir
Description
Evaluation of discharge
Limits of application
Selected list of references

FLUMES
Long-throated flumes
Description
Evaluation of discharge
Modular limit
Limits of application
Description
Evaluation of discharge
Modular limit
Limits of application
Throatless flumes with broken plane transition
Description
Parshall flumes
Description
Evaluation of discharge
Submerged flow
Accuracy of discharge measurement
Loss of head through the flume
Limits of application
H-flumes
Description
Evaluation of discharge
Modular limit
Limits of application
Selected list of references

Orifices
Circular sharp-edged orifice
Description
Determination of discharge
Limits of application
Rectangular sharp-edged orifice
Description
Determination of' discharge
Modular limit
Limits of application
Constant-head-ori fice
Description
Determination of discharge
Limits of application
Radial or tainter gate
Description
Evaluation of discharge
Modular limit
Limits of application
Crump-De Gruyter adjustable orifice
Description
Evaluation of discharge
Limits of application
Metergate
Description
Evaluation of discharge
Metergate installation
Limits of application
Neyrpic module
Description
Discharge characteristics
Limits of application
Danaïdean tub
Description
Evaluation of discharge
Limits of application
Selected list of references

MISCELLANEOUS STRUCTURESDivisors
Description
Evaluation of discharge
Limits of application
Pipes and small syphons
Description
Evaluation of discharge
Limits of application
Fountain flow from a vertical pipe
Description
Evaluation of discharge
Limits of application
Flow from horizontal pipes
Description
Evaluation of discharge
Limits of application
Brink depth method for rectangular canals
Description
Evaluation of discharge
Limits of application
Dethridge meters
Description
Evaluation of flow quantity
Regulation of discharge
Limits of application
Propeller meters
Description
Factors affecting propeller rotation
Head losses
Meter accuracy
Limits of application
Selected list of references

ANNEX 1
Basic equations of motion in fluid mechanics
Introduction
Equation of motion-Euler
Equation of motion in the s-direction
Piezometric gradient in the n-direction
Hydrostatic pressure distribution in the m-direction

ANNEX 2
The overall accuracy of the measurement of flow
General principles
Nature of errors
Sources of errprs
Propagation of errors
Coefficient errors
Example of error combination
Selected list of references
Errors in measurements of head
Error in discharge volume over long period

ANNEX 3
Side weirs and oblique weirs
Introduction
Side weirs
General
Theory
Practical C,-values
Practical evaluation of side weir capacity
Oblique weirs
Weirs in trapezoïdal channels
Selected list of references

ANNEX 4
Suitable stilling basins
Introduction
Straight drop structures
Common drop
U.S. ARS basin
Inclined drops or chutes
Common chute
SAF Basin
Riprap protection
Determining maximum stone size in riprap mixture
Filter material placed beneath riprap
Permeability to water
Stability of each layer
Filter construction
Selected list of references

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