Changes between Version 24 and Version 25 of Tutorial/AdvancedParticleImagingVelocimetry2


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Timestamp:
Jan 16, 2015, 10:50:56 AM (10 years ago)
Author:
vaillant1p
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  • Tutorial/AdvancedParticleImagingVelocimetry2

    v24 v25  
    1414= Sub_background =
    1515We observe parasitic light rays on the images which correspond to fixed features, leading possibly to spurious velocity vectors equal to 0. To eliminate those we use '''sub_bacground'''.
    16 Open the image with 'series' and select the program 'sub_background'. This function is not provided in the default menu, so you need to use the last menu option 'more...', and select the function in the sub-folder 'series/' of the package uvmat. This option is then preserved in the menu for later use.
     16In the GUI uvmat, select '''Run/field series'''. In the GUI 'series' and select the program 'sub_background'. This function is not provided in the default menu, so you need to use the last menu option 'more...', and select the function in the sub-folder 'series/' of the package uvmat. This option is then preserved in the menu for later use.
    1717Then run '''sub_background''' over the whole index range in i and j, using the default parameters. Answer Yes to the question 'apply levels', which will conveniently rescale the image brightness after background removal.
    1818
    … …  
    2222Choose the pair 'j=1-2' which provides the smaller time interval (100 ms), a good choice to capture correlations in a first try (although higher precision can be obtained with a larger time interval if the correlation is still of good quality).
    2323
    24 Select the Mask 'mask_1.png' previously created.
     24Select the check box Mask and open the file 'mask_1.png' previously created.
    2525
    2626Looking at the results with uvmat, we see the global flow features. We notice however that the thin parietal plume is not properly resolved while the precision in the interior is poor because of the small displacement within the frame pair. So the next step will be to perform two PIV series optimized for each sub-region and merge them.