Streamlines, streaklines, and pathlines

The current line is a term used in fluid dynamics. Power lines are geometric tool for illustrative description of a flow.

Power lines are curves in the velocity field of a fluid, the tangent direction coincide with the directions of the velocity vectors, i.e., at any point in the power line is affected by a velocity vector. They convey a vivid impression of the instantaneous flow field and indicate problematic flow regions (eg flow separation ).

All streamlines of a stream together form the stream tube.

The streamlines are along with railway lines, streaklines and timelines components of the visualization concept of " characteristic lines ".

In a steady flow the streamlines coincide with the particle trajectories. In unsteady flow, however, not because the power lines a picture of the currently existing velocity directions show the particle trajectories, however, represent the passage of time occupied by a particle velocity directions.

Power lines can be in steady flows experimentally in the wind tunnel, for example, at a Autoumströmung, make them visible. Most, however, can be seen in the wind tunnel railway lines or brush lines.

Properties

• Power lines can have no kinks and also not cut, because at one point can not also rule two different flow rates.
• However, a contraction ( moving together ) of the flow lines is subsonic acceleration of the flow in the supersonic delay.
• Diverging streamlines show a delay in the subsonic flow, supersonic acceleration.
• For curved streamlines of the pressure in the centrifugal direction increases.
• In rectilinear, parallel current lines, there is no pressure change across the current line.
• Orthogonal to current lines are the lines of constant potential.

Calculation

Be with a three-dimensional flow field.

The power lines are curves which extend in each point tangential to the instantaneous speed field. It is therefore

In parameter-free representation