wiki:Tutorial/AdvancedParticleImagingVelocimetry2

Version 7 (modified by sommeria, 8 years ago) (diff)

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This is an example using more advanced tools than the examples .... and .... Image pre_processing and merging of mutiple fields. Open the example UVMAT_DEMO_FILES/EX07_convection .

calibration

mark corners

mask

sub_background

first PIV

making two masks

The parietal jet requires a very good resolution, particularly among x. To limitate PIV to this jet, let us create a specific mask. Open the previously created contour polygon contour_mask.xml in uvmat by the menu bar Tools/Projection object/browse.... Check the box edit (tag [CheckEditObject]) in the frame Object of uvmat (right hand side) to allow editing of the polygon. then replace the lower x bound 0 by 52. Then create the corresponding mask by Tools/make mask, save it with name Dalsa1.mask/mask_plume.png. Similarly create a mask for the bulk Dalsa1.mask/mask_bulk.png, with bounds in x [0 55].

PIV on the parietal plume

Choose the following parameters:

  • pair j=1-2 for Civ1 and Civ2 : it minimises the time interval which is needed to capture the large velocity in the plume.
  • CorrBox x,y=(5 31) which optimizes the resolution in x (5 pixels)
  • Search x, y=(25 55) which allows for a larger velocity component along y .
  • auto-grid Dx=2, Dy=10, consistent with CoorBox (about half the box size).
  • Mask selected, with name .../Dalsa1.mask/mask_plume.png .
  • For Civ2, same parameters CorrBox, auto-grid and Mask.
  • For patch and Fix, default parameters.

PIV on the interior

Select the pair j=1-3 to deal with the small velocities (considering that the parietal plume has been masked). Then use the default parameters.

merging data on a common grid

create a projection grid in phys coordinates. For that open a velocity field with uvmat, displayed in phys coordinates. Use the upper bar menu option Projection object/plane. Then in the GUI set_object, choose the option ProjMode=interp_lin. Choose a mesh 0.2 cm in each direction, ranging from 0 to 55 in x and 0 to 58.8 in y. Press REFRESH to see the result of projection in the GUI view_field.

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