Explain streamlines and streamline flow.

Explanation

The path of motion of a fluid particle is called a line of flow.
The path taken by a fluid particle under a steady flow is a streamline.
Streamline : The curve whose tangent at any point is in the direction of the fluid velocity at that point.

(a) A typical trajectory of a fluid particle.
Path of particle is shown in figure (a). It indicates streamline .The velocity of particle at a point is in the direction of tangent drawn at that point .
the flow for which such streamlines can be defined is called streamline flow.
In unsteady flow , flow of line can be defined but not defined streamline.