Tracking Free-Surfa...
 

[Solved] Tracking Free-Surface of SPH Particles  

 

pjay
 pjay
(@pjay)
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September 26, 2019 7:33 pm  

Hi All,

I am currently going through the LS-DYNA example of the dam-break wave generated by SPH particles ( https://www.dynaexamples.com/sph/intermediate-examples/wavestructure ) and I was wondering if there is a way to extract along a vertical line the free-surface elevation over time? Or conversely a 3D output of the free-surface of the SPH particles over time.

Thank you all for your time and consideration!


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Negative Volume
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September 29, 2019 12:38 am  

Hi @pjay

So you are wanting to get the output of the maximum height of the wave for a specific plane over time? Is that correct? 


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pjay
 pjay
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September 29, 2019 3:02 pm  

Hi @negativevolume,

Yes that is correct, ideally I would like to take these measurements and compare them to experimental results from a flume to provide some sort-of calibration parameter. My initial thought is that you wouldn't be able to output a plane but rather a 3D shape as a SPH particle may never actually pass over that specific plane.

Cheers!

 


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Negative Volume
(@negativevolume)
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November 7, 2019 12:10 pm  

@pjay

Did you ever find a solution to this? The only thing that I could think of would be going to Model -> Section and then creating a vertical section plane which you can drag to find the max height at a certain point in time. I believe you can also take some measurements using it. 


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pjay
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November 9, 2019 3:15 pm  

@negativevolume

I never ended up finding a solution in LS-DYNA, I ended up creating a image processing script that used a video file output from LS-DYNA to extract the surface elevation, it is quite cumbersome though... Can't say I have ever tried using the vertical section plane, by drag do you mean basically setting the height of the section plane to be inline with the particles? I have also thought about trying to use tracers to export particle motion but what I have found is I would need a lot in order to get an accurate estimate.


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Negative Volume
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November 10, 2019 4:40 pm  

@pjay

Yeah so using the section plane function in Prepost to cut a number of sections and identify where the peak wave is and find what the height is. I've attached a picture below to show an example of this. You can even play the animation while keeping the cuts which may be useful to you. 

 

1573404036-section_cuts.png

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pjay
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December 14, 2019 5:29 pm  

In case anyone comes across this problem as well. Another solution is to output your D3plot at a suitable rate and reduce the parts showing to only the SPH particles then go to Output > Select Active Parts only, select Nodal Coordinates, enter in the Append St No (state sequence to output) and save the file as a keyword format. You now have a file that outlines all SPH coordinates for all states output in a nice format that you can process however needed.


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Negative Volume
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December 17, 2019 2:34 am  

@pjay

Does this output over multiple time states? I’ve only ever used it for single time point.


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pjay
 pjay
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December 17, 2019 1:24 pm  

@negativevolume

Yes the "Append State No" takes the following form:

start state : end state : n -> creating a file from the start state to the end state and output the states at a frequency of n. 


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Negative Volume
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December 17, 2019 9:32 pm  

@pjay

Very cool, did not know that. 


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