Changes between Version 28 and Version 29 of Tutorial/ParticleImageVelocimetry

Timestamp:

Jan 21, 2015, 2:16:26 PM (9 years ago)

Author:

vaillant1p

Comment:

--

Tutorial/ParticleImageVelocimetry

@@ -45 +45 @@
 [[Image(contours.JPG)]]
 
-To get the vorticity field, 'vort' , and other spatial derivatives, you need to come back to the GUI''' series''' with images as input and action civ_series'''. '''In''' civ_input''', select the check boxes '''[FIX1] ''' and  '''[PATCH1] ''' , validate the input with '''[OK]''', then press '''[RUN]''' in the GUI '''series'''. A question box appears to warn about the existence of the result file, answer '''[OK]''' to refresh it with the new data. This will produce an interpolated velocity field and their spatial derivatives in the same netcdf file.  After this operation vorticity can be visualized in the GUI  '''uvmat''', selecting the option 'vort'''' ''' in the popup  menu '''[FieldName]'''.
+To get the vorticity field, 'vort' , and other spatial derivatives, you need to come back to the GUI''' series''' with images as input and action civ_series'''. '''In''' civ_input''', select the check boxes '''[FIX1] ''' and  '''[PATCH1] ''' , validate the input with '''[OK]''', then press '''[RUN]''' in the GUI '''series'''. A question box appears to warn about the existence of the result file, answer '''[OK]''' to refresh it with the new data. This will produce an interpolated velocity field and their spatial derivatives in the same netcdf file.  After this operation vorticity can be visualized in the GUI  '''uvmat''', selecting the option 'vort'''' ''' in the popup  menu '''[!FieldName]'''.
 
 == Superposing image and vectors ==
@@ -73 +73 @@
 Now repeat the PIV operation to include the time information in the result (in the absence of time information the file index is taken as default value).
 
-To introduce  the geometric calibration, use the method described in [https://servforge.legi.grenoble-inp.fr/projects/soft-uvmat/search?q=wiki%3ATutorial%2FGeometricCalibration geometric calibration], section 'Simple scaling'. The velocity field is then displayed in terms of physical velocity. To come back to the image coordinates, use the box''' [!!TransformName]''' on the left : select to blank instead of ’phys’.
+To introduce  the geometric calibration, use the method described in [https://servforge.legi.grenoble-inp.fr/projects/soft-uvmat/search?q=wiki%3ATutorial%2FGeometricCalibration geometric calibration], section 'Simple scaling'. The velocity field is then displayed in terms of physical velocity. To come back to the image coordinates, use the box''' [!TransformName]''' on the left : select to blank instead of ’phys’.
 
 Note that the netcdf file has not been by changed by calibration, whose rescaling is introduced after reading the file. This means that calibration can be provided, and possibly updated, after the PIV processing.
@@ -80 +80 @@
 The first parameter to adjust is the time interval between images, which should be sufficiently long to provide a displacement of a few pixels. The measurement precision is typically 0.2 pixel, so that a displacement of 4 pixels, as in the example, provides a relative precision of 5 %. A larger displacement would be preferable in terms of precision but may yield to poor image correlation and ’false vectors’.
 
-Once the image pair has been chosen, the main parameters are the size of the correlation box in both directions ('''[num_!CorrBoxSize]_1]''' and '''_2''') and the size of the search box, ('''[num_! SearchBoxSize_1]''' and '''_2'''), expressed in pixels. For each velocity vector, the correlation box is moved within the search box to optimise the image correlation between the two sub-images inside the correlation box. To allow for a displacement of d pixels, the search box size must exceed the correlation box by at least d+2 on both sides, so 2d+4. A systematic shift '''[num_!SearchBoxShift_1]''', and '''_2''', can be also introduced to minimise the search area in the presence of a mean flow.
+Once the image pair has been chosen, the main parameters are the size of the correlation box in both directions ('''[num_!CorrBoxSize]_1]''' and '''_2''') and the size of the search box, ('''[num_!SearchBoxSize_1]''' and '''_2'''), expressed in pixels. For each velocity vector, the correlation box is moved within the search box to optimise the image correlation between the two sub-images inside the correlation box. To allow for a displacement of d pixels, the search box size must exceed the correlation box by at least d+2 on both sides, so 2d+4. A systematic shift '''[num_!SearchBoxShift_1]''', and '''_2''', can be also introduced to minimise the search area in the presence of a mean flow.
 
 The parameter '''[num_!CorrSmooth]''' is used to fit the correlation data with a smooth function to obtain the maximum with sub-pixel precision. We generally keep the default value 1.