Handling concavity in ListContourPlot

Questions
1

I have imported some CFD results (in csv format) into Mathematica to do some further processing of the data.

One of my 2D geometries is as:

Geometry.png
Geometry.png1622×698 101 KB

Now, when I try to do the contour plot, I get the following:

ScreenShot2019-12-10at4.21.48PM.jpg
ScreenShot2019-12-10at4.21.48PM.jpg1956×802 196 KB

Why is contour plot filling those areas above and below the narrow section with purplish color. Those regions are not even within my X and Y coordinates (see the image for geometry above)?

Any ideas?

Thanks

Cross-posted here.
I am attaching a sample of my data (a csv file for the above geometry). Note that I am only working with columns 1 and 2 (as x and y) and column 6, as my velocity in z direction.

tube_arbitrary.csv (762 KB)

2

Can you post the exact code you use to create your plots? It’s not obvious how to get from the CSV to your plots.

3

Looks very similar to this question.

4

Cross-posted here.

Which is also mentioned in the original post.

5

To import the csv file:

       tubeArbitrary = Import["tube_arbitrary.csv", "HeaderLines" -> 1];

To extract the x and y, each in a separate list:

       XtubeArbitrary = tubeArbitrary[[All, 1]];

       YtubeArbitrary = tubeArbitrary[[All, 2]];

To extract x and y and U velocity in z direction in a single data-set:

        XYUtubeArbitrary = tubeArbitrary[[All, {1, 2, 6}]];

To plot the geometry based on the (x,y) points:

   ListPlot[Thread[{XtubeArbitrary, YtubeArbitrary}], PlotRange -> Automatic, AspectRatio -> Automatic];

To contourplot it:

      ListContourPlot[XYUtubeArbitrary, Contours -> 500, ColorFunction -> "Rainbow", ContourStyle -> None, AspectRatio -> Automatic, PlotLegends -> Automatic];
6

Hello Mohammad,

a ‘quick and dirty’ method would be to just cutting off the bottom using PlotRange:

ListContourPlot[xyutubeArbitrary, Contours -> 500, 
 ColorFunction -> "Rainbow", ContourStyle -> None, 
 AspectRatio -> Automatic, PlotLegends -> Automatic, 
 PlotRange -> {.004, Automatic}]

ppp.png
ppp.png444×237 32.6 KB

Does that help? Regards – Henrik

7

I’ve suggested another hacky solution here Stack Exchange

8

Thanks. It is useful.