Hydraulic Chapter 1

8/2/2019 Hydraulic Chapter 1

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Hidayat Jamal & ZulhilmiismailHydraulics & HydrologyDepartment, FKA, UTM

OPEN CHANNEL FLOWChapter 1


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Assessment

Asg 1 (Individu C1-C6): 10% Lecture 1 submit L7

Test 1 (C1-C3): 15% Lecture 4/5

Asg 2 (Group C1-C5): 10% Lecture 1 submit L8Test 2 (C3-C5): 15% Lecture 7/8

Final: 50% No Lecture (after study break)

GOOD LUCK

2


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Assignment/Project format/instruction

Size: A4 with margin of 2.54 cm (1 inch) all side

Font: 12 (Times new roman)

Binding: RingFront page: Title, subject, topic, members, lecturer

Penalty for late submission

GOOD LUCK


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Open channel flow

Significance-essential for water resources development;

-Designs of irrigation, navigation, spillways,sewers, and drainage.

-Rivers management


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CHAP 1: INTRODUCTION to ocf

What is Open Channel?

Implies flow in channel open to the atmosphere.Driven by gravity.Water flow in a river is driven by the elevationdifference.Depth usually unknown & normally function ofdischarge and geometry.


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Many different types-Stream; River or creek, canal, flume &culverts

Many different cross-sectional shapes


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Natural flows: streams,rivers, creeks, floods, etc.

Human-made systems:fresh-water aqueducts,

irrigation, cannal, sewers,drainage ditches, etc.

Classification of Open-Channel Flows


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Type ofOpen

Channel

SteadyFlow

UniformFlow

Non-uniform

Flow

RapidlyVaried Flow

GraduallyVaried Flow

UnsteadyFlow

Types of Flow Chart


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Types of Flow

Steady uniform flow-constant depth in time and distanceSteady non-uniform flow-depth varies with distance but not timeUnsteady flow-depth varies with both time and distance


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Steady and Unsteady Flow

Unsteady

Steady

Flow Rate

Time


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In one flow, the flow type may change:


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Flow in a channel is uniform if the flow depthremains constant.

Uniform Flow


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State of Flow

Reynolds Number

-Laminar flow (Re500)

-Transition flow (if 500 Re 1000)

-Turbulent flow (Re 1000)

VRRe


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State of Flow

Froude Number

-Subcritical flow, Fr 1

-Critical flow, Fr = 1

gD

VFr


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Definition of Geometric Elements

y = depth of flow

T = Top width

b @ B = bottom channel

width

z = side slope

So = channel bottom slope

v = average flow velocity


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Parameters of Open Channels

A = Area of the flow cross-section

P = Length of the line of contact between the channeland the water on the area

R = A / P (the average flow depth/hydraulic radius)

D = A / T (hydraulic water depth)

Cross-SectionArea

Wetted Perimeter


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Geometrical properties


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Freeboard

Vertical distance between the highest water levelanticipated in the design and the top of the retaining

banks. It is a safety factor to prevent the overtopping ofstructures.


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Example 1

Given Rectangle channel cross-sectionwith depth of flow 1.2m, channel width 2m

and freeboard 0.6m. Find T, A, P, R and D?


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Solution

Flow depth, y = 1.2m

Top width, T = 2m

A = y x B= 1.2 x 2= 2.4m2

P = 1.2 + 2 +1.2= 4.4m

T

AD

P

AR

m545.0

4.4

4.2

m2.12

4.2


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Example 2

Given Trapezoidal channel cross-sectionwith depth of flow 1.0m, channel width

0.5m, freeboard 0.2m and channel sideslope 1:1. Find T, A, P, R and D?


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Solution

Flow depth, y = 1.0m

Top width, T = B + 2zy

= 0.5 + 2 (1)(1)= 0.5 + 2= 2.5m

A = (B + zy) x y= (0.5 + (1)(1) x (1)

= 1.5m2 6.0T

AD

45.0P

AR

212 zyBP

2)1(1)1(25.0

33.3225.0


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Hydraulic Chapter 1

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