Fluid_Kinematics_Presentation_6666.pptxx

HARAMAYA INSTITUTE OF TECHNOLOGY, DEPARTMENT OF CIVIL ENGINEERING
HYDRAULICS PRESENTATION
Submission date: mon,may 19
SECOND YEAR,2ND SEMESTER IN 2024/25 (SECTION 2)
GROUP MEMBERS ID NUMBER
1. JATANI HUKA ----------------------------------------- 1671/16
2. SAWI SIRJI ------------------------------------------- 2388/16
3. ABDULAZIZ KADER---------------------------------- 0450/16
4. ABDULAZIZ NIBRAS--------------------------------- 0447/16
5. BARISO AHMED------------------------------------ 0796/16
6. ROBEL LAMESA-------------------------------------- 2325/16
7. ALVADO MADOK--------------------------------------- 4304/16
8. RIHANA AWELL -------------------------------------- 2313/16
9. FEROMSA ADEM------------------------------------ 1300/16
10. REBIRA TILAHUN----------------------------------- 2280/16 SUMMISSION BY : MR.SEAD BURHAN

FLUID KINEMATICS

Fluid kinematics is a branch of fluid mechanics which deals with the studyof
velocity and acceleration of the particles of the fluids in motion and their
distribution in space without considering any force or energy causing the
motion.
There are two approaches to describe the motion of a fluid and its associated
properties.
1. Lagrangian approach 2. Eulerian approach

2. Eulerian approach

 In this method the observer concentrates on the movement of a single
particle track (or follow) its path as it moves, and monitor change in its
properties.
The properties may be velocity, temperature, density, mass, or acceleration,
etc in the flow field.



Applications of Lagrangian Approach
1. Modeling the behavior of blood in the cardiovascular system
2. Studying the dispersion of pollutants in the atmosphere or ocean
This method entails the follow and shortcomings
1. Cumbersome and complex.
2. It can be difficult to track the motion of particles in a crowded flow
3. The equations of motion are very difficult to solve and the motion hard to
understand.
2. Eulerian approach (a field approach)

Identify (or label) a certain fixed location in the flow field and follow change in
its property, as different materials pass through that location.

In the Eulerian method the observers concern is to know what happens at any
given point in the space, which is filled by fluid in motion, what are the
velocities, acceleration, pressure, etc at various parts at a given time.


This method is almost exclusively used in fluid mechanics, especially because of its
mathematical simplicity.

In fluid mechanics we are not concerned with the motion of each particle, but we study the
general state of motion at various points in the fluid system.

Therefore, Eulerian method is mostly used because it is more useful in theanalysis of the
majority of engineering problems.

DIMENSION OF FLOW

A Fluid flow said to be one (1D), two (2D) or three-dimensional flow (3D)
depending up on the number of independent space coordinate (x,y,z) &
required to describe the flow.

When the dependent variables (example, velocity, pressure density etc) are
a function of one space co-ordinate say x- coordinate) it is known as one-
dimensional flow.

Example of one –dimensional flow (1D): flow through pipes & channels,
between boundaries, etc. if the velocity distribution is considered constant
at each cross-section.
‘’One-dimension’’ is taken along the central streamline of the flow
dependent variables vary only with x- direction (or s- direction).

• When the dependent variables vary only with two-space coordinates, the
flow is known as two-dimensional flow (2D).
Example: Flow over a weir
V=(u,v)=(0.5 + 0.8x)i + (1.5 – 0.8y)j
Generally a, fluid is a rather complex three- dimensional, time dependent
phenomenon, i.e., V= V(x, y, z, t).
In almost any flow situation, the velocity field actually contains all three-
velocity components (u, v, w) & each is a function of all three-space
coordinates (x, y, z).
Example of a 3D flow: the flow of air past an airplane wing provides a
complex three-dimensional flow.

Velocity

Velocity of fluid particle
➢ In general, fluids flow from one point in space to another point as a
function of time. This motion of fluid is described in terms of the velocity &
acceleration of the fluid particles.

Velocity of fluid along any direction can be defined as the rate of change of
displacement of the fluid along that direction.

At a given time instant, a description of any fluid property (such as density,
pressure,Velocity, & acceleration) may be given as a function of the fluids
location.
An infinitesimal change in velocity

i.e. V = u (x, y, z, t)i +v (x, y, z, t)j + w (x, y, z, t)k is given by:

Acceleration

Acceleration of fluid particle

Acceleration of fluid element along any direction can be defined as the rate of
change of velocity of the fluid along that direction.
The acceleration components An infinitesimal change in velocity are given
by:

Fluid_Kinematics_Presentation_6666.pptxx

Describing the pattern of flow
Although fluid motion is complicated, there are various concepts that can
beused to help in the visualization & analysis of flow fields.
This pattern of flow may be described by mean of streamlines, stream
tubes,path lines and Streak lines.
1. Stream lines: - it is an imaginary curve drawn through a flowing fluid in
such a way that the tangent to it at any point gives the direction of the velocity
of flow at those points.

Streamlines don’t cross or intersect each other.

 The velocity vector at point must be tangent to the streamline at that
point.
Therefore: dy/dx = tan0 = v/u
udy -vdx = 0

2. Stream tube: - is a tube imaginated to be formed by a group of
streamlines passing through a small closed curve.
- A fluid can enter or leave a stream tube only at its ends
3. Path line: - a path line is a line traced out by a given single fluid
particle as it moves from one point to another over a period of time.
-In steady flow path lines & streamlines are identical
4. Streak lines: - A streak line consists of all particles in flows that have
previously passed through a common point. They can be obtained by
taking instantaneous photographs of marked particles that all passed
through a given location in the flow field at some earlier time.
 In experimental work often a color or a dye is injected in the flowing
fluid, in order to trace the motion of the fluid particles. The resulting trail
of color is known as streak lines.


For steady flow, each successively injected particle follows precisely behind
the previous one, forming a steady streak line that is exactly behind the
previous one,forming a steady streak line that is exactly the same as the
streamline through the injection point.

Hence, path line, streamlines & streak lines are the same for steady flows.
Types of flow
A. Classification according to type of fluid
(i) Ideal fluid flow – the fluid is assumed to have no viscosity. The velocity
distribution is thus assumed uniform ---- (idealized)
(ii) Real fluid flow: viscosity is taken in to consideration, which leads to the
development of shear stress b/n moving layers.

(iii)Compressible fluid flow: - if variation of pressure results in considerable
changes in volume & density.
Eg… Gases are generally treated as compressible.
Iv) Incompressible fluid flow - if extremely large variation in pressure is required
to affect very small changes in volume.
B. Classification according to variation of velocity, displacement and etc
(i) Steady flow: - A flow is said to be steady if at any point in the flowing fluid
characteristic such as velocity, pressure, density etc.. don’t change with time.
However this characteristic may be different at different points in the flowing fluid.

(ii) Unsteady flow: - if at any point in the flowing fluid any one of allof the characteristics, which
describes the behavior of fluids in motion changes with time.
(iii) Uniform flow: - this occurs when the velocity both in magnitude & direction remains
constant with respect to distance i.e. it doesn’t change from point to point.
Example: flow of fluid under pressure through long tube of constant diameter.
(iv) Non- uniform flow: - if there is a change in velocity either in magnitude or
direction with respect to distance , then:

(V) Laminar flow: - in laminar flow the particles of fluid move in orderly
manners & the steam lines retain the same relative position in successive cross
section. Laminar flow is associated with low velocity of flow and viscous fluids.
(vi)Turbulent flow: - Here the fluid particles flow in a disorder manner
occupying different relative positions in successive cross section. Turbulent
flow is associated with high velocity flows.
 Around 1883, Reynolds established the boundary between the laminar and
turbulent flow,using the dimensionless number called Reynolds’s number, Re.
Re =ρ / μ =VD/v Where; v = μ / p
𝑉𝐷
where:
V- mean velocity Re < 2000 ------- laminar flow
D- Diameter Re > 4000 ------- Turbulet flow
 v- Kinematics viscosity In b/n 2000 and 4000 its is Transition

Fluid_Kinematics_Presentation_6666.pptxx

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