Posted by
Gary Settles on
Jan 19, 2020; 5:18pm
URL: http://imagej.273.s1.nabble.com/Turbulent-Jet-Morphology-tp5022840p5022842.html
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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