Module 1: Introduction to Hydraulics
Kevin J. Tanguin, MSCE
Civil Engineering Department
FEU-Institute of Technology
1T 2022-2023
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Outline
1
Introduction
2
Distinction Between Fluid Mechanics and Hydraulics
3
Fundamentals of Fluid Flow
4
Idealization of Fluid
5
Classification of Fluid Flow
6
Description of Fluid Flow
7
Flow Patterns
8
Equations for Fluid Flow
9
Sample Problem
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Introduction
Introduction
Hydraulics is derived from the greek word
hudour which means water.
Hydraulics is the science that deals with the
mechanical behavior of water at rest or in
motion.
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Introduction
Introduction
Mechanical Behavior:
Forces and energy of fluids at rest
Energy and momentum of fluids in motion
Water surface elevation
Discharge and velocity
Hydrostatics and Hyrdrodynamics
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Distinction Between Fluid Mechanics and Hydraulics
Fluid Mechanics vs. Hydraulics
Fluid mechanics is the study of fluids under all conditions of rest and motion.
It has more emphasis on employing the principles of
Physics.
Usually deals with all types of fluids.
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Distinction Between Fluid Mechanics and Hydraulics
Fluid Mechanics vs. Hydraulics
Hydraulics is more empirical.
Problems are solved based on the results of previous
studies and available data.
Mostly focused on water.
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Distinction Between Fluid Mechanics and Hydraulics
Fluid Mechanics vs. Hydraulics
Hydraulics can be construed as an applied
science of Fluid Mechanics.
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Fundamentals of Fluid Flow
Fundamentals of Fluid Flow
Three significant concepts in fluid flow are:
The principle of conservation of mass, from which the
equation of continuity is developed,
The principle of conservation of energy, from which the
flow equations are derived, and
The principle of conservation of momentum, from which
equations evaluating dynamic forces exerted by flowing
fluids may be established.
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Fundamentals of Fluid Flow
Fundamentals of Fluid Flow
Properties of Fluid:
!
m kg
ρ=
V m3
!
w N
γ=
V m3
!
1 m3
V̇ =
γ N
γfluid
ρfluid
SG =
=
ρwater
γwater
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Idealization of Fluid
Idealization of Fluid Flow
Ideal Fluid
An ideal fluid may be defined as one in which there is
no friction; that is its viscosity is zero.
Such a fluid does not exist in reality.
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Idealization of Fluid
Idealization of Fluid Flow
Real Fluid
Tangential or shearing forces always comes into being
whenever motion takes place, thus giving rise to fluid
friction.
These friction forces are due to a property of the fluid
called viscosity
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Classification of Fluid Flow
Classification of Fluid Flow
Steady Flow
The velocity at every point remains constant with respect to time.
Unsteady Flow
The velocity changes with time.
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Classification of Fluid Flow
Classification of Fluid Flow
Uniform Flow
The magnitude and direction of the velocity do not
change from point to point in the fluid.
Non-uniform (Varied) Flow
The velocity, depth, pressure, etc., change from point
to point in the fluid flow.
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Description of Fluid Flow
Description of Fluid Flow
Control Volume
is a finite volume through which fluid flows in and out.
2
1
control volume
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Description of Fluid Flow
Description of Fluid Flow
Lagrangian Description
A way of looking at fluid motion where the observer
follows an individual fluid parcel (fluid particle) as it
move through space and time.
But, fluid is a continuum.
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Description of Fluid Flow
Description of Fluid Flow
Eulerian Description
A way of looking at fluid motion that focuses on specific locations in space through which the fluid flows
as time passes.
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Flow Patterns
Flow Patterns
Streamlines
are imaginary curves drawn through a fluid to indicate
the direction of motion in various sections of the flow
of the fluid system.
is a curve that is everywhere tangent to the instantaneous local velocity vector.
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Flow Patterns
Flow Patterns
Pathlines
is the actual path travelled by an individual fluid particle over some period of time.
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Flow Patterns
Flow Patterns
Streaklines
is the locust of points of fluid particles that have passed
sequentially through a prescribed point in the flow.
If your insert a small tube into a flow and introduce a
continuous stream of a trace fluid, the observed pattern
is a streakline.
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Flow Patterns
Flow Patterns
For steady flow:
Streamlines, pathlines and streaklines are identical.
For unsteady flow:
Streamlines represent the instantaneous flow.
Streaklines and pathlines are flow patterns that have
some age and thus indicate a time history.
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Equations for Fluid Flow
Flow Rate
Flow rate is the quantity of fluid flowing in a system per
unit time.
Simplifying Assumptions:
The fluid is ideal. The fluid has no viscosity.
The flow is incompressible. Density of the fluid does
not change significantly throughout the system.
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Equations for Fluid Flow
Flow Rate
Volume Flow Rate:
Q = av
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where:
Q - discharge, m3 /s
a - area of the conduit, m2
v - velocity of flow, m/s
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Equations for Fluid Flow
Flow Rate
Mass Flow Rate:
ṁ = ρQ
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where:
ṁ - mass flow rate, kg/s
ρ - density of fluid, kg/m3
Q - discharge, m3 /s
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Equations for Fluid Flow
Flow Rate
Weight Flow Rate:
ẇ = γQ
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where:
ẇ - weight flow rate, N/s
γ - unit weight of fluid,
N/m3
Q - discharge, m3 /s
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Equations for Fluid Flow
Common Conversions
Unit Weight of Water:
Volume:
1 m3 = 1000 liters
1 gallon = 3.785 liters
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kg
1000 m
3
lb
62.4 ft 3
9810 mN3
9.81 kN
m3
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Sample Problem
Sample Problem
The inside diameter of a pipe is 50 mm. If water of unit
weight 9.59 kN/m3 is flowing through it at an average
velocity of 8 m/s, find:
1
2
3
Volume Flow Rate
Weight Flow Rate
Mass Flow Rate
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Sample Problem
End.
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Sample Problem
References
Cruise, J., Sherif, M., & Singh, V. (2007). Elementary Hydraulics
CENGAGE Learning
Cengel, Y. & Cimbala, J. (2017). Fluid Mechanics: Fundamentals
and Applications. (4th Ed.) McGraw-Hill Education
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