We
were discussing the basic definition of kinematics of flow in the subject of fluid
mechanics in our recent post. Now we will start a new topic in the field of fluid
mechanics i.e. Types of fluid flow with the help of this post.

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There
are following types of fluid flow as mentioned here.

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**Steady and unsteady flow**

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*Steady flow*

*Steady flow*

Steady
flow is basically defined as the flow in which, the properties of fluid such as
density, velocity, pressure at a point do not change with time.

In
simple, if a fluid flow is not a function of time then that flow will be termed
as steady flow. Flow
of water with constant discharge through a pipe line will be considered as
steady flow.

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*
Un-steady flow*

*Un-steady flow*

Un-steady
flow is basically defined as the flow in which, the properties of fluid such as
density, velocity, pressure at a point changes with time.

In
simple, if a fluid flow is a function of time then that flow will be termed as
unsteady flow. Flow
of water with varying discharge through a pipe line will be considered as
unsteady flow.

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**Uniform and non-uniform
flow**

Uniform
flow is basically defined as the flow in which, the properties of fluid such as
density, velocity, pressure at a given time do not change with respect to space.

Non-uniform
flow is basically defined as the flow in which, the properties of fluid such as
density, velocity, pressure at a given time changes with respect to space.

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**Laminar flow and Turbulent
flow**

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**Laminar
flow **

Laminar flow is basically defined as that type of flow in which the fluid particles
will move along the well defined paths or streamlines. These streamlines will
be straight and parallel with each other. Therefore in case of laminar flow,
particles will move in laminas or layers, smoothly gliding over each other.

Laminar
flow provides the information that fluid flow will be organized, slow,
parabolic profile, parallel to vessel walls etc. Laminar flow will not produce
any sound.

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**Turbulent flow **

Turbulent
flow is basically defined as the flow in which the particles of fluid will move
in zig-zag way. As fluid particles will move in zig-zag way in turbulent flow,
there will be formation of eddies and that will be responsible for high energy
loss. Turbulent
flow will produce sound and can be heard also.

Let
us consider we have one pipe and fluid is flowing through this pipe. Type of fluid
flow will be determined on the basis of a non-dimensional number i.e. Reynolds’s
number.

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**Reynolds’s number, Re = ρVD/μ**

Where,

D
= Diameter of pipe through which fluid is flowing

V=
Velocity of fluid flow

ρ
= Density of the fluid

μ
= Viscosity of the fluid

If
Reynolds’s number is less than 2000, fluid flow will be considered as laminar
fluid flow. Laminar flow is also termed as viscous flow or stream-line flow.

If
Reynolds’s number is more than 2000, fluid flow will be considered as turbulent
fluid flow.

If
Reynolds’s number is in between 2000 and 4000, fluid flow will be considered as
transitional fluid flow.

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**
Compressible and
incompressible flow**

Compressible
flow is basically defined as the flow in which the density of the fluid will be
changed from point to point. In simple words we can say that, density of the
flowing fluid will not be constant.

Incompressible
flow is basically defined as the flow in which the density of the fluid will not
changed from point to point. In simple words we can say that, density of the
flowing fluid will be constant.

For
compressible flow, Density (ρ) ≠ constant

For
incompressible flow, Density (ρ) = constant

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**Rotational and irrotational
flow**

Rotational
flow is basically defined as the flow in which fluid particles while flowing
along the stream lines will also rotate about their own axis.

irrotational
flow is basically defined as the flow in which fluid particles while flowing
along the stream lines will not rotate about their own axis.

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**One, two and three dimensional
flow**

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**One dimensional flow**

One
dimensional flow is basically defined as the flow in which the flow parameters such
as velocity will be a function of time and one space co-ordinate only.

For
one dimensional steady fluid flow, velocity will be a function of one space
co-ordinate only. Variation of velocities in other two mutually perpendicular directions
will be negligible.

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**Two-dimensional flow**

Two-dimensional
flow is basically defined as the flow in which the flow parameters such as
velocity will be a function of time and two rectangular space co-ordinates
only.

For
two-dimensional steady fluid flow, velocity will be a function of two space
co-ordinates only. Variation of velocity in third direction will be negligible.

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**
Three-dimensional flow**

Three-dimensional
flow is basically defined as the flow in which the flow parameters such as
velocity will be a function of time and three space co-ordinates.

For
three-dimensional steady fluid flow, velocity will be a function of three space
co-ordinates.

We
will discuss the basic concept of rate of flow or discharge in the subject of
fluid mechanics in our next post.

Do
you have any suggestions? Please write in comment box.

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**Reference:**

Fluid mechanics, By R. K. Bansal

Image
Courtesy: Google

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