TYPES OF FORCES ACTING IN MOVING FLUID

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.

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.

Inertia force (F_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)

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)

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)

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)

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)

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.

Reference:

Fluid mechanics, By R. K. Bansal

Image Courtesy: Google

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