Learning Forum

[Karthik Remella]

Is there any difference between pathlines, streaklines and streamlines?

[prajput]

Hi @Kremella  ,

A pathline is the path or line or trajectory traced out by a single moving particle.

A line joining all these fluid particles which pass through a specific point in space is referred to as a streakline.

Streamlines are lines in the flow field such that at a given instant of time are tangential to the velocity vectors at every spatial location in a flow field. Hence, the flow cannot cross a streamline. 

[Keyur Kanade]

Hello @Kremella , In simpler terms, A pathline show the trajectory of a single particle over time. A streakline is typically used in experiments. Releasing ink in water at a specific position, we practically mark the particles passing at that location. After some time, these particles would be at different locations. The line formed is a streakline. Streamlines are lines tangent to the local velocity of the fluid. They are obtained using only the velocity vectors at a given instant of time.

[prajput]

Btw one note to add. For steady flows they are all the same, while this is not true for unsteady flows.