Fluid flow
The science which deals with the geometry of motion of fluids without reference to the forces causing the motion is known as hydro-kinematics or simply kinematics.
There
are in general two methods by which the motion of fluid may be described. These
are Lagrangian method and Eulerian method.
Lagrangian: in the Lagrangian method any individual fluid particle is selected, which is pursued throughout its course of motion and observation is made about the behaviour of this particle during its course of motion through space.
Eulerian: on the other hand, in the Eulerian method any point in the space occupied by the fluid is selected and observation is made of whatever change of velocity, density and pressure which take place at that point.
According to different considerations fluid flows may be classified in several ways as follows:
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2. Uniform
flow and Non-uniform flow.
3. One-dimensional
flow, Two-dimensional flow and Three-dimensional flow.
4. Rotational
flow and Irrotational flow.
5. Laminar
flow and Turbulent flow.
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Steady flow: fluid flow is said to be steady if at any point in the flowing fluid various characteristics such as velocity, pressure, density, temperature etc., which describe the behaviour of the fluid in motion, do not change with time.
Unsteady flow:
Fluid
flow is said to be unsteady if at any point in the flowing fluid any or all the
characteristics which describe the behaviour of the fluid in motion change with
time. Thus, flow of fluid is unsteady, if at any point in the flowing fluid
Uniform
flow:
When
the velocity of the flow of fluid does not change, both in magnitude and
direction, from point to point in the flowing fluid, for any given instant of
time, the fluid is said to be uniform.
Non-uniform flow:
If
the velocity of the flow of fluid changes from point to point in the flowing
fluid at any instant, the flow is said to be non-uniform.
One-dimensional, Two-dimensional and Three-dimensional flow:
The various characteristics of flowing fluid such as velocity, pressure, density, temperature etc., are in general the functions of space and time i.e., these may vary with the coordinates of any point x, y and z and time t. Such a flow is known as a three-dimensional flow.
When the various characteristics of flowing fluid are the functions of only any two of the three-coordinate directions and time t, i.e., these may not vary in any of the directions, then the flow is known as two-dimensional flow.
When the various characteristics of flowing fluid are the functions of only one of the three coordinate directions and the time t, i.e., these may vary only in one direction, then the flow is known as one-dimensional flow.
Types of flow
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Unsteady
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Steady
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Three-dimensional
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V= f(x, y, z, t)
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V= f(x, y, z)
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Two-dimensional
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V= f(x, y, t)
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V= f(x, y)
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One-dimensional
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V= f(x, t)
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V= f(x)
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Rotational flow: a flow is said to be rotational if the fluid particles while moving in the direction of flow rotate about their mass centres.
Irrotational flow: a flow is said to be irrotational if the fluid particles while moving in the direction of flow rotate about their mass centres.
Laminar flow: a flow is said to be laminar when the various fluid particles move in layers (or laminae) with one layer of fluid sliding smoothly over an adjacent layer. Thus, in the development of a laminar flow, the viscosity of the flowing fluid plays a significant role.
Turbulent
flow: a fluid motion is said to be turbulent
when the fluid particles move in an entirely haphazard or disorderly manner,
that results in a rapid and continuous mixing of the fluid leading to momentum
transfer as flow occurs. In such a flow eddies or vortices of different sizes
and shapes are present which move over large distances. These eddies and their
random movement give rise to the fluctuations in the velocity and the pressure
at any point in the flow field, which are necessarily the functions of time. Thus,
at any point in turbulent flow the velocity and pressure are the functions of
time thereby rendering such a flow as unsteady.
Various Fluid Flow patterns. Click here....
Various Fluid Flow patterns. Click here....
