Kinematics --  The branch of dynamics that describes the properties of pure motion without regard to force, momentum or energy.

 

The vector velocity field can be broken down kinematically into four properties:  (a)  Translation;  (b) Divergence; (c) Vorticity; and, (d) Deformation.  The three dimensional velocity field is always a combination of one  or more of the following four kinematic “components.”

 

1.  Translation – fluid elements translate with the speed of the wind.

 

2.  Divergence –  fluid elements experience a change in area.

 

3.  Vorticity –  fluid elements rotate.

 

4.  Deformation –  fluid elements change shape.

 

A fluid in which no changes in area occur is known as nondivergent.  A fluid in which no rotation occurs is known as irrotational.