Changes between Version 26 and Version 27 of Tutorial/ParticleImageVelocimetry
 Timestamp:
 Jan 21, 2015, 11:46:08 AM (9 years ago)
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Tutorial/ParticleImageVelocimetry
v26 v27 106 106 '''* FIX1''': Select the ’'''FIX1'''’ operation, which eliminates some false vectors using several criteria. Use the default parameters. 107 107 108 '''* PATCH1''': Select the ’'''PATCH1'''’ operation, to interpolate the vectors on a regular grid and calculate spatial derivatives. Select a high resolution [nx]=100, [ny]=30, number of grid points in which the velocity will be interpolated. These values correspond to dx=dy=10 pixels for an image 1000x300. Choose the default value 10 for the smoothing parameter ’rho’. You can later try different values, the smoothing effect increasing with rho. Keep the default values for the other parameters.108 '''* PATCH1''': Select the ’'''PATCH1'''’ operation, to interpolate the vectors on a regular grid and calculate spatial derivatives. Choose the default value 10 for the smoothing parameter '''[!!FieldSmooth]'''. You can later try different values, the smoothing effect increasing with '''!!FieldSmooth'''. Keep the default values for the other parameters. 109 109 110 '''* CIV2''': Select the ’'''CIV2'''’ operation to improve the correlation results, using the information on local image deformation, provided by the previous knowledge on velocity spatial derivatives (calculated in patch1). Use a finer grid dx= dy=5 than for civ1. The spatial resolution can be slightly improved by decreasing the correlation box, using for instance Bx,By=(15,11). The s earch range is determined automatically using the prior knowledge on velocity, obtained with the civ1 and patch1 operations. Note that ’civ2’ corresponds to a new measurement from the images, the previous civ1 and patchoperations being used only as an initial guess for the search of optimal correlations.110 '''* CIV2''': Select the ’'''CIV2'''’ operation to improve the correlation results, using the information on local image deformation, provided by the previous knowledge on velocity spatial derivatives (calculated in patch1). Use a finer grid dx= dy=5 than for civ1. The spatial resolution can be slightly improved by decreasing the correlation box, using for instance Bx,By=(15,11). The shift of the search range is here given at each point by the prior estimate from Civ1, so that the search range can be optimized: choose [21,17] which provides a margin of 3 pixels on each side of the correlation box. Note that ’civ2’ corresponds to a new measurement from the images, the previous civ1 and patch1 operations being used only as an initial guess for the search of optimal correlations. 111 111 112 Then select ’'''FIX2'''’ and ’'''PATCH2'''’ with the same parameters as ’'''FIX1'''’ and ’'''PATCH1'''’.112 Then select ’'''FIX2'''’ and ’'''PATCH2'''’ with the default parameters. 113 113 114 114 '''* Running the calculation''': Press '''[RUN]''' to run the calculation. The results are stored in a new subdirectory, CIV_1, so the previous results are not erased (you can also set the name of the subdirectory in the GUI, by the edit boxes '''[SubDirCiv1]''' and '''[SubDirCiv2]'''. The existing subdirectories are listed above. … … 123 123 124 124 [[Image(vort_civ32.jpg)]] [[Image(vort_vel_zoom.jpg)]] 125 126 == Fix and patch ==127 == Civ2 ==128 == Civ3 ==