Quaid-e-Awam University of Engineering, Science and Technology Department of Civil Engineering Hydraulics / Irrigation Laboratory OBJECT:
Characteristics of flow through a Venturi Flume.
APPARATUS:
Self-contained glass sided Tilting flume, Venturi Flume Assembly, Instrument carrier Hook and point gauge.
THEORY:
General discharge equation Q ca 2 g ( h h1 )
a = throat area = bh1
Where C Cd 1 /(1 m 2 )
m = a/A, A = upstream area B.h.
Standing wave equation Q 2 2g
3
3bh 3 / 2 1.704bh 3 / 2
FLUME: This term is applied to devices in which the flow is locally accelerated due to the following: 1. A streamlined lateral contraction in the channel sides 2. The combination of the lateral contraction, together with a streamlined hump in the invert (channel bed).
VENTURI FLUME: A venturi flume is a critical-flow open flume with a constricted flow which causes a drop in the hydraulic grade line, creating a critical depth.
APPLICATION OF VENTURI FLUME: It is used in flow measurement of very large flow rates, usually given in millions of cubic units. Flumes are usually designed to achieve critical flow in the narrowest (throat) section, together with a small afflux. Flumes are especially applicable where deposition of solids must be avoided (e.g., in sewage works or in irrigation canals traversing flat terrain).
Quaid-e-Awam University of Engineering, Science and Technology Department of Civil Engineering Hydraulics / Irrigation Laboratory PROCEDURE: Form the venture flume in the working section of the flume, by fixing an asymmetrical throat insert to each wall. Then measure and note the throat width. Level the flume, prior to opening the inlet valve and admitting water into the flume. Maintaining a constant flow, measure and note, h, hc, h1 and Q. Increasing the flow in stages, measure and note the above for each stage. Observe the drowned and standing wave flow conditions.
RESULTS AND CALCULATIONS:
Q
h
hc
h1
B
Plot Q against (h-h1), Q against h, and Q against h1. Determine Cd.
B
h-h1
Quaid-e-Awam University of Engineering, Science and Technology Department of Civil Engineering Hydraulics / Irrigation Laboratory
Quaid-e-Awam University of Engineering, Science and Technology Department of Civil Engineering Hydraulics / Irrigation Laboratory
Quaid-e-Awam University of Engineering, Science and Technology Department of Civil Engineering Hydraulics / Irrigation Laboratory
Short Questions
Q#1: What have you learned from this experiment?
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Quaid-e-Awam University of Engineering, Science and Technology Department of Civil Engineering Hydraulics / Irrigation Laboratory _______________________________________________________________________________ _
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Q#2: What are the situation where a venture flume can be used as a discharge measuring device?
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Quaid-e-Awam University of Engineering, Science and Technology Department of Civil Engineering Hydraulics / Irrigation Laboratory _______________________________________________________________________________ _
Q#3: What is difference between venture flume and weir?
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Q#4: What is difference between venture flume and venturemeter?
Quaid-e-Awam University of Engineering, Science and Technology Department of Civil Engineering Hydraulics / Irrigation Laboratory
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Q#5: comment on the effects of narrowing the channel. Is it the same as raising the bed? What factors influence the efficiency of the venture flume?
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Quaid-e-Awam University of Engineering, Science and Technology Department of Civil Engineering Hydraulics / Irrigation Laboratory
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Quaid-e-Awam University of Engineering, Science and Technology Department of Civil Engineering Hydraulics / Irrigation Laboratory
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