Using PIVlab with many particle image

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Ronan Kervil Ronan Kervil
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Using PIVlab with many particle image

Hi, I'm currently working on particle transport and I'm wondering if I can correctly measure a velocity field with PIVlab in my situation.
 Indeed the particles are distributed like a 'jet' configuration, with high density in the middle of the jet and low density on the border.
When I measure horizontal speeds (jet's axis) with PIVlab, velocity decrease in the middle of the jet and my main problem is to know if this come from an artefact or from a physical property!

 All in all, how can I easily determine the uncertainties of the speeds with varying particles' density?

If you have the time, here is a link to download a typical image sequence :
https://dl.univ-lyon1.fr/zzza9lkh1

Thank you in advance, and if I'm not clear feel free to ask me anything.

Ronan
Ronan Kervil Ronan Kervil
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Re: Using PIVlab with many particle image

To illustrate this :

The right side is a tendency curve showing horizontal velocities u evolving with respect to vertical axis y.
 
 Finally here is a mean of ten horizontal velocities coming from a ROI of 80 pixel horizontal thickness and 800 pixels height, with standard deviation as error bars, versus the vertical axis y (varying from 0 to 100*8 pixels)  



I may worry for nothing but I want to be sure that speed maxima correspond to lowest density without PIV artefact (due to a saturation of interrogation area for example or this density shift).
If you got any opinion on that, I'll take it!

Thanks,
Ronan

 

William William
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Re: Using PIVlab with many particle image

Hi,
this is a difficult question... I don't see a reason why your results should be incorrect. But I never worked with image data that has these high density gradients. When you're not sure if you want to trust the results, the only way to verify this would be to generate artificial images with similar properties (you could again simulate a jet with a high gradient in particle density). You can have a look at the particle image generator of PIVlab to get a quick start.

Please consider donating for the PIVlab project:
http://paypal.me/pools/c/81Y8wBVi4y

The developer needs to update to a recent Matlab release in order to keep the project running.

Ronan Kervil Ronan Kervil
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Re: Using PIVlab with many particle image

Hi,

thank you for replying, I was thinking to that too. So, when the ''synthetic test'' will be done, I'll keep you inform via the forum.

Ronan