what is the difference between timeline, pathline, streakline and streamline in fluid mechanics?

Question

what is the difference between timeline, pathline, streakline and streamline in fluid mechanics?

Answer 1

Timeline: a curve formed by tracking initially adjacent particles in time. It shows how particles deform. Consider a curve drawn through adjacent particles at t=0. At some other time t>0, the particle may no longer be adjacent. The curve connecting them at t>0 is the timeline.



Pathline: the path or trajectory traced out by moving particle. It tells how the particle has translated.



Streakline: curve formed by connecting all fluid particles passing through a fixed point in space. This is formed by picking any point and letting the flow pass through it. Then at some later time, you "freeze" the flow and draw a curve connecting the particles that passed through that point in the order in which they passed.



Streamline: curves drawn in flow at a fixed instant which are tangent to the direction of flow at every point. Basically a streamline is a curve drawn tangent to the velocity vector of fluid.



BTW, for steady flow, the pathline, streamline, and streakline are identical.

Answer 2

Streamline Fluid Mechanics

Answer 3

Also clothesline, frontline, partyline, flatline and redline.

Answer 4

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