Draw streamlines through a flow field

Documentation

Status: draft. Verified steps and screenshots to come.

Draw streamlines through a velocity field and color them by a second variable. Two programs do it here: ParaView and MATLAB. Time: 10 minutes

A vector field holds a direction and a speed at every point of the data. Arrows show a sample of it. Streamlines connect those samples into curves, so a recirculation appears as a closed loop and a stagnant region as a gap.

Choose your program

Each version is a complete lesson on its own page. Pick the program you use.

Choose your program
Program Lesson Practice data The second variable Minutes
ParaView Draw streamlines in ParaView disk_out_ref.ex2: air around a heated, spinning disk Temperature, colored along each line 10
MATLAB Draw streamlines in MATLAB (page to come) MATLAB's sample wind data Wind speed, colored along each line 10

ParaView reads simulation output directly: Exodus, VTK, NetCDF, OpenFOAM and CSV. Use MATLAB if your velocity data is already in MATLAB arrays.

What each program's result looks like

Both pictures come from the lessons' own scripts.

Streamline tubes in the outlined flow domain: a dome over the heated disk, yellow near the disk, dark purple higher up where the air is cooler
Figure 1. ParaView: streamlines through disk_out_ref.ex2, colored by temperature. Yellow is the hottest air.
Wind streamlines colored by speed: mostly blue slow lines, green to yellow where the wind is fastest, a slow spiral near the ground
Figure 2. MATLAB: streamlines through MATLAB's wind data, colored by wind speed. Yellow is the fastest wind.

What every version teaches

A streamline is a curve that is tangent to the velocity everywhere along it. Both versions build one by putting down starting points, the seeds, and following the field from each in small steps. The seeds are a choice you make: they decide which part of the flow the picture shows, and a region no streamline reaches does not appear. Both lessons then color the curves by a second quantity, temperature in ParaView and speed in MATLAB, so one figure shows the path and the value along it.

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