HYDRAULICS
FUNDAMENTALS OF FLUID FLOW
INTRODUCTION
FLUID FLOW
FUNDAMENTALS
The movement of fluid which is referred as
“flow” describes how particles behave with
each other and the surrounding environment
just like how water moves through a pipe
system distributed to many households. The
study concerned with this movement of fluid is
fluid dynamics and is applied in many fields
such as aeronautics, machineries, medical field
(blood circulation), pipeline system (water, oil,
gases) etc
Hydraulics is derived from the Greek words
hudro (water) and aulos (pipe)
INTRODUCTION
FLUID FLOW
FUNDAMENTALS
Although it is clear that fluid motion follows
certain definite laws and principles, the
effect of the immediate surroundings and
the essential characteristics of these laws
are relatively difficult to define and so far,
no mathematical relation has yet been
developed to completely describe fluid
motion.
Mathematical and experimental outputs
have been combined which gave rise to
what is known as empirical hydraulic.
INTRODUCTION
HYDRAULICS
➢
➢
➢
more empirical
problems are solved based on
results of previous
experimentations
mostly focused on water
Hydraulics is actually, an applied science
of Fluid Mechanics.
FLUID FLOWS ASSUMPTIONS
Lagrangian Fluid Flow
“A way of looking at fluid
motion where the observer
follows an individual fluid
parcel as it moves through space
and time. Plotting the position of
an individual parcel through time
gives the path line of the parcel.
This can be visualized as sitting
in a boat and drifting down a
river.”
Eulerian Fluid Flow
“a way of looking at fluid
motion that focuses on specific
locations in the space through
which the fluid flows as time
passes. This can be visualized
by sitting on the bank of a river
and watching the water pass the
fixed location.”
Fluid Flow Classification
Steady State Flow
“Steady flow means steady with respect to time.
Thus the flow at every point remains constant with
respect to time.”
Uniform Flow
“The flow is defined as uniform flow when in the flow field
the velocity and other hydrodynamic parameters do not
change from point to point at any instant of time.”
Unsteady State Flow
“In unsteady flow the flow changes
with time.”
Non-uniform Flow (Varied)
“When the velocity and other hydrodynamic
parameters changes from one point to
another the flow is defined as non-uniform.”
TYPES OF FLOW
STEADY AND UNSTEADY FLOW
The flow is said to be steady when discharge at a certain point in the system does not change for a period
of time.
TYPES OF FLOW
UNIFORM AND NON-UNIFORM FLOW
The flow is said to be uniform when the velocity of fluid (both magnitude and direction) at all points in a
system is the same.
Fluid Flow Classification
Laminar Flow
▪Involves almost parallel layer of
streamlines.
▪Nearly parabolic velocity profile.
▪Commonly observe to high
viscous fluid with low velocity.
▪Re < 2000
Turbulent Flow
•It is describe to chaotic and uncertain flow
regime.
•Unstable velocity profile, it follows
Logarithmic function.
•More on high velocity and low viscous fluid.
•Re > 4000
©2017 Google Image
TYPES OF FLOW
The Reynolds number is a dimensionless quantity used to classify the fluid flow in relation to the effect of
viscosity and velocity to the flow pattern of a fluid. It is expressed as:
𝒗𝑫𝝆
𝑹𝒆 =
where 𝑣= velocity
𝝁
D= pipe diameter
ρ=density
μ= dynamic viscosity
𝜇
since v=𝜌
𝑹𝒆 =
𝒗𝑫
𝐯
v= kinematic viscosity
FLOW RATE
Fluid Dynamics is a branch of fluid mechanics that deals with the study of how fluid behaves when in
motion. This study follows the principles of conservation of energy, momentum and continuity equation
which are applied singly or in combination in solving fluid motion problems.
Discharge (Flow rate) Q, is the amount of fluid passing through a specific section along a conduit or
passage per unit of time (m3/s ,lit/s, ft3/s). It can also be expressed as mass flow rate M (kg/s or slug/s)
and weight flow rate W (N/s or lb/s).
Q=AV
where Q= discharge, flowrate (m3/s ,lit/s, ft3/s), volume flux,
A= area (m2, ft2)
V= velocity (m/s, ft/s)
FLOW RATE
(Q=AV)ρ
multiply both sides by density, ρ
Qρ= (m2)(m/s)(kg/m3)
Qρ=kg/s ------>unit for mass flow rate, M
M= Qρ
M= Qρ
multiply both sides by acceleration due to gravity, g
Mg= Qρg
from γ=ρg
(kg/s)(m/s2)= Qγ
N/s= Qγ
N/s is the unit for weight flow rate W
W= Qγ
CONTINUITY EQUATION
Continuity uses the conservation of mass to describe the relationship between the velocities of a fluid in
different sections of a system. The simple observation that the volume flow rate must be the same throughout
a system provides a relationship between the velocity of the fluid through a pipe and the cross-sectional area.
SAMPLE PROBLEMS
Water flows through a 75mm diameter pipe at a velocity of 3m/s. Find:
a) Volume Flow rate in 𝑚3 /𝑠 and lit/sec
b) Mass flow rate in kg/sec
c) Weight flow rate in N/sec
SAMPLE PROBLEMS
Air at 30deg.Celsius and 110KPa abs flows at 20N/s through a rectangular duct that measure 160mm x
320mm. Compute the average velocity and volume flux, use gas constant R= 287 J/ Kg-K
SAMPLE PROBLEMS
A fluid flows at 0.001 𝑚3 /𝑠 through a 100mm diameter pipe. Determine whether the flow is laminar or
turbulent if the fluid is:
a. Hydrogen with kinematic viscosity of 1.08x10-4 m2/s
b. air with kinematic viscosity of 1.51x10-5 m2/s
c. gasoline with kinematic viscosity of 4.06x10-7 m2/s
SAMPLE PROBLEMS
A 100mm diameter plunger is being pushed at 60mm/sec into a tank filled with oil (0.82). Find the weight flow
rate in N/s of oil being forced out at a 30mm diameter hole.
Q out
Q in
LABORATORY REPORT NO.1
REYNOLD’S NUMBER