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.