Draw streamlines through a flow field

Documentation overview

Status: draft. Verified steps and screenshots to come.

In this lesson you will draw streamlines that follow a velocity field, and add a second variable to the picture. Time: 10 minutes ยท Branch: Vector fields

Arrows give the direction of a flow at single points. Streamlines follow it, so recirculation, dead zones and mixing show up as shapes you can recognise. The same steps work on other vector fields: water velocity, magnetic fields, ion flux, wind.

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 opens simulation output as written: Exodus, VTK, NetCDF, OpenFOAM and CSV. MATLAB suits velocity arrays that are already in MATLAB.

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

Streamlines start from seeds. Each line is traced from a starting point, its seed, by following the flow direction step by step. The picture you get is therefore of the flow near the seeds, and nowhere else. If a region you care about looks empty, move or spread the seeds before deciding nothing happens there. Color the lines by a second variable, temperature or speed, and one picture carries both where the flow goes and what it carries.

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