We were
discussing the basic concept of streamline
and equipotential line, dimensional
homogeneity, Buckingham
pi theorem, difference
between model and prototype and basic principle of similitude i.e. types of similarity in the subject of fluid mechanics, in our recent posts.

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Now we
will go ahead to understand the various forces acting on moving fluid in the
field of fluid mechanics with the help of this post.

We will see another important topic in the field of fluid mechanics i.e.
Types of forces acting in moving fluid with the help of this post.

There are
various types of forces, as mentioned here, acting on moving fluid. Forces acting
on a fluid mass may be any one or combinations of the several of the following
forces.

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**Inertia force (F**_{i})

_{i})

Inertia
force is basically defined as the force which is the product of mass and
acceleration of the flowing fluid. Inertia force will act on flowing fluid in a
direction opposite to the direction of acceleration.

Inertia
force will be displayed by F

_{i}and will always exist in the fluid flow problems.###
**Viscous force (F**_{V})

_{V})

Viscous
force is basically defined as the force which is the product of shear stress
due to viscosity and surface area of the flowing fluid.

Viscous
force will be displayed by F

_{V}and will always exist in the fluid flow problems when viscosity will be in very important role.###
**Gravity force (F**_{g})

_{g})

Gravity
force is basically defined as the force which is the product of mass and
acceleration due to gravity of the flowing fluid.

Gravity
force will be displayed by F

_{g}and will always exist in case of open surface fluid flow problems.###
**Pressure force (F**_{P})

_{P})

Pressure
force is basically defined as the force which is the product of pressure
intensity and cross-sectional area of the flowing fluid.

Pressure
force will be displayed by F

_{P}and will always exist in case of pipe flow problems.###
**
Surface tension force (F**_{S})

_{S})

Surface
tension force is basically defined as the force which is the product of surface
tension and length of surface of the flowing fluid.

Surface
tension force will be displayed by F

_{S}.###
**Elastic force (F**_{e})

_{e})

Elastic force
is basically defined as the force which is the product of elastic stress and area
of the flowing fluid.

Elastic force
will be displayed by F

_{e}.
There will
be one or two forces out of above mentioned forces, which will dominate the
other forces. These dominating forces will govern the fluid flow problems.

We will
see another important topic i.e. Dimensionless numbers and Model laws or similarity laws

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