Re: Turbulent Jet Morphology?

Posted by Frank Shaffer on Jan 19, 2020; 5:58pm
URL: http://imagej.273.s1.nabble.com/Turbulent-Jet-Morphology-tp5022840p5022843.html

Hello Professor Settles,
Thank you for the suggestions. I certainly will try them.
I don't know if you remember, but I worked at a DOE lab in Pittsburgh.  If
I recall correctly, you also were using a copper-vapor laser for flow viz.
Boy were they a headache to use! Now it can all be done with LED's.
I'm now working with Professor Savas at UC Berkeley.
Best regards,
Frank

On Sun, Jan 19, 2020 at 12:40 PM Gary Settles <[hidden email]> wrote:

> Hello Frank,
>
> Herbie’s suggestion is a good one. I’ll make a few more, based on my
> experience using ImageJ to analyze turbulent jets (line-of-sight-integrated
> optical images, though, not fluorescence).
> 1) Load your video as an image stack into ImageJ. Draw a line on the image
> stack indicating the location of the line of pixels to be resliced (e.g.
> jet
> centerline). Then use Image Stacks Reslice followed by keyboard button “/”.
> What you get is called, in ImageJ, a “pseudo-linescan” image, but note that
> the x,y,z stack in ImageJ is actually an x,y,t stack, where t is the
> timeline of your video. With proper calibration this streak image will give
> you eddy velocity data.
> 2) You can see the FFT of an entire image using Process FFT, but a better
> way (for me) is to use the plugin “nr realft”, which needs a 32-bit
> grayscale image with a selected line segment of length = a power of 2. This
> yields a power spectrum plot along the selected line. With some experience
> you’ll see that there is a lot more that ImageJ can do with turbulent
> flows.
>
> Gary Settles
> Dist. Prof. Emeritus of M. E., Penn State
>
>
>
>
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>
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