Changes between Version 65 and Version 66 of UvmatHelp


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Jun 12, 2013, 6:34:23 PM (7 years ago)
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sommeria
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  • UvmatHelp

    v65 v66  
    704704== 11 - PIV: Particle Imaging Velocimetry ==
    705705=== 11.1 Overview ===
    706 PIV can be performed by selecting the Matlab function ''civ_series'' as '''[ActionName]''' in the GUI '''series'''. The same operations can be also performed with the older function ''civ.m'' running with the specific GUI '''civ.fig''', accessible from uvmat by the menu bar command '''[RUN/civ]'''. This older option is still used to run the fortran programs [CIVx].
    707 
    708 -''' {Opening the GUI:} ''' The GUI '''civ.fig''' for PIV calculation can be directly opened by the command '>>civ' on the Matlab prompt. Then open an image or a documentation file (.xml ) with the file browser. ''' '''The''' ''' GUI '''civ.fig''' can be also directly opened from '''uvmat.fig''', by the menu bar command '''[RUN/civ]'''.  A third way is just to open the Matlab image ({civ.fig} file) stored after each processing in the directory of the velocity fields. Then just edit it and run a new calculation.
     706PIV can be performed by selecting the Matlab function ''civ_series'' as '''[!ActionName]''' in the GUI '''series'''. The same operations can be also performed with the older function ''civ.m'' running with the specific GUI '''civ.fig''', accessible from uvmat by the menu bar command '''[RUN/civ]'''. This older option is still used to run the fortran programs [CIVx].
     707
     708-''' Opening the GUI: ''' The GUI '''civ.fig''' for PIV calculation can be directly opened by the command '>>civ' on the Matlab prompt. Then open an image or a documentation file (.xml ) with the file browser. ''' '''The''' ''' GUI '''civ.fig''' can be also directly opened from '''uvmat.fig''', by the menu bar command '''[RUN/civ]'''.  A third way is just to open the Matlab image ({civ.fig} file) stored after each processing in the directory of the velocity fields. Then just edit it and run a new calculation.
    709709
    710710<doc78|center>
    711711
    712 -''' {Input file name and indexing:} ''' The root name of the input file is displayed in the edit box '''[RootName]''', and a set of indices can be defined by the edit boxes '''[first_i] ''' (first index), '''[incr_i]''' (increment), '''[last_i ]'''(last index). The GUI offers a wide variety for the choice of image pairs to correlate. In the case of two file indices i and j, a mode for the choice of image pairs can be selected in the popup menu '''[mode]'''. -*'pairj1-j2': a given pair of j indices (or subscript a, b c...) can be chosen in the CIV1 menu '''[list_pair_civ1]''', while the corresponding indices i are set by '''[first_i] ''', '''[incr_i]''' , '''[last_i ]'''. -*'series(Di)': a sliding set of i index pairs is chosen by a set of {reference} indices i_ref given by '''[first_i] ''', '''[incr_i]''' , '''[last_i ]''' and a pair interval defined in '''[list_pair_civ1]''': the first choice 0|1 corresponds to the sliding pair i_ref|i_ref+1. the second choice -1|1 to the sliding pair i_ref-1|i_ref+1,...This mode is generally used with a single image series or movie, but it can be also used in volume scan, with a second index j chosen by '''[first_j] ''', '''[incr_j]''' , '''[last_j ]'''. -*'series(Dj)': operates like 'series(Di)', but with sliding j index pairs. -*comparing two image series: this is made possible by selecting 'displacement' in the popup menu '''[compare]''', which gives access to a browser for selecting the second image series. This second series can be reduced to a single reference image, if it contains no index. The displacement field with respect to this reference image is then obtained  for successive times.  -*stereo PIV: this option in the menu '''[compare]''' provides the three velocity components  by comparing the stereoscopic views from two cameras, see [section 10.6->#sec10.6].
    713 
    714 -''' {Succession of operations:} '''
    715 
    716 The CIV process involves a succession of iterative operations:  -*civ1: the initial image correlation process. -*fix1: detection of 'false' velocity vectors according to different criteria. -*patch1: interpolation and filtering on a regular grid, providing access to spatial derivatives of the velocity (diverrgence, curl, strain). -* civ2: advanced image correlation algorithm using the result of civ1 as a first approximation. -* fix2 and patch2: similar as fix1 and patch1, but applied to the civ2 results. This series of operations is chosen by selecting the corresponding  check boxes on the left, which give access to the corresponding parameter input panels. Note that the result of each of these operations is stored in the output netcdf file, so the process can be split in several runs. When an existing netcdf velocity file is opened, the GUI '''civ.fig''' is automaticaly configured to perform the next operation (fix1, patch1, civ2...) needed in the process.
     712-''' Input file name and indexing: ''' The root name of the input file is displayed in the edit box '''[RootName]''', and a set of indices can be defined by the edit boxes '''[first_i] ''' (first index), '''[incr_i]''' (increment), '''[last_i ]'''(last index). The GUI offers a wide variety for the choice of image pairs to correlate. In the case of two file indices i and j, a mode for the choice of image pairs can be selected in the popup menu '''[mode]'''. -*'pairj1-j2': a given pair of j indices (or subscript a, b c...) can be chosen in the CIV1 menu '''[list_pair_civ1]''', while the corresponding indices i are set by '''[first_i] ''', '''[incr_i]''' , '''[last_i ]'''. -*'series(Di)': a sliding set of i index pairs is chosen by a set of {reference} indices i_ref given by '''[first_i] ''', '''[incr_i]''' , '''[last_i ]''' and a pair interval defined in '''[list_pair_civ1]''': the first choice 0|1 corresponds to the sliding pair i_ref|i_ref+1. the second choice -1|1 to the sliding pair i_ref-1|i_ref+1,...This mode is generally used with a single image series or movie, but it can be also used in volume scan, with a second index j chosen by '''[first_j] ''', '''[incr_j]''' , '''[last_j ]'''. -*'series(Dj)': operates like 'series(Di)', but with sliding j index pairs. -*comparing two image series: this is made possible by selecting 'displacement' in the popup menu '''[compare]''', which gives access to a browser for selecting the second image series. This second series can be reduced to a single reference image, if it contains no index. The displacement field with respect to this reference image is then obtained  for successive times.  -*stereo PIV: this option in the menu '''[compare]''' provides the three velocity components  by comparing the stereoscopic views from two cameras, see [section 10.6->#sec10.6].
     713
     714-''' Succession of operations: '''
     715
     716The CIV process involves a succession of iterative operations: 
     717 * civ1: the initial image correlation process.
     718 * fix1: detection of 'false' velocity vectors according to different criteria.
     719 * patch1: interpolation and filtering on a regular grid, providing access to spatial derivatives of the velocity (diverrgence, curl, strain).
     720 * civ2: advanced image correlation algorithm using the result of civ1 as a first approximation.
     721 * fix2 and patch2: similar as fix1 and patch1, but applied to the civ2 results.
     722
     723This series of operations is chosen by selecting the corresponding  check boxes on the left, which give access to the corresponding parameter input panels. Note that the result of each of these operations is stored in the output netcdf file, so the process can be split in several runs. When an existing netcdf velocity file is opened, the GUI '''civ.fig''' is automaticaly configured to perform the next operation (fix1, patch1, civ2...) needed in the process.
    717724
    718725=== 11.2 CIV1: ===
    719726The image pair is selected in the menu '''[list_pair_civ1]''', see sub-section 10.1. The time interval of the image pair must be chosen sufficiently small to provide a good correlation, and sufficiently large to provide good measurment precision: a displacement of 5-10 pixels is generally optimum.
    720727
    721 The time interval for each image pair is indicated in '''[list_pair_civ1]''' iif the information is made available, either from a movie file, or from a detected xml file (with the name RootName.xml). The source of the timing information is indicated in the edit box '''[ImaDoc]'''. Examples of xml files are provides in /XML_SCHEMAS/ImaDoc_templates. In the absence of information, the file index is taken for the time.  The time interval for a given index pair may change with time, so the time interval display is taken for given reference indices, given by '''[i_ref]''' and ''' [j_ref].'''.
     728The time interval for each image pair is indicated in '''[list_pair_civ1]''' iif the information is made available, either from a movie file, or from a detected xml file (with the name !RootName.xml). The source of the timing information is indicated in the edit box '''[ImaDoc]'''. Examples of xml files are provides in /XML_SCHEMAS/ImaDoc_templates. In the absence of information, the file index is taken for the time.  The time interval for a given index pair may change with time, so the time interval display is taken for given reference indices, given by '''[i_ref]''' and ''' [j_ref].'''.
    722729
    723730('''[ibx], [iby])''' set the size (in pixels) of the 'correlation box', the sliding window used to get image correlations. '''[isx],[ isy]''' set the size of the 'search box' in which image correlation is calculated, see figure.  This search box can be shifted with respect to the correlation box by parameters  ([shift x],[shift_y]). This is useful in the presence of a known mean flow.
     
    739746The velocity results are stored in the subdirectory set by the edit box '''[subdir_civ1].''' Use the browser''' [list_subdir_civ1]''' to check the existing subdirectories.
    740747
    741 -''' {RUN and BATCH:} '''
     748-''' RUN and BATCH: '''
    742749
    743750The PIV calculation is started by the press button [RUN], or [BATCH] if this option has been installed. BATCH sends the same computations as background computing tasks in a network.
     
    814821||Patch1(2)_SubDomain||estimated nbre of vectors in a subdomain||
    815822||Civ2_CheckDecimal||=1 if decimal shift option is used (reduced peaklocking)||
    816 ||Civ2_CheckDeformation|=1 if image deformation option is used||
     823||Civ2_CheckDeformation||=1 if image deformation option is used||
    817824
    818825-'''List of variables:'''
     
    888895-*Names of field variables for civ2 and patch2
    889896
    890 |   |  '''        civ2'''          | '''interp2'''  |        '''filter2 '''          | | dim.  |        nb_vectors2  |        nb_vec2_patch  |        nb_vec2_patch  | |x          |vec2_X          |vec2_patch_X  |        vec2_patch_X | |y          |         vec2_Y  |        vec2_patch_Y |         vec2_patch_Y | |z          |        vec2_Z |         vec2_patch_Z  |        vec2_patch_Z | |u                  |vec2_U |         vec2_patch0_U  |        vec2_patch_U | |v                   |vec2_V          |vec2_patch0_V  |        vec2_patch_V | |w           |        vec2_W          |vec2_patch0_W|          vec2_patch_W | |correlation  |        vec2_C  |          |          | |warning flag  |        vec2_F |          |          | |false flag  |        vec2_FixFlag |          |          | |du/dx  |         |vec2_patch0_DUDX          |vec2_patch_DUDX          | |du/dy  |         |vec2_patch0_DUDY          |vec2_patch_DUDY          | |dv/dx  |         |vec2_patch0_DVDX          |vec2_patch_DVDX          | |dv/dy  |         |vec2_patch0_DVDY          |vec2_patch_DVDY          |
     897same as previous, replacing 'vec' by 'vec2'.
    891898
    892899---------------