Changes between Version 5 and Version 6 of Tutorial/ParticleImageVelocimetry


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Timestamp:
Sep 2, 2013, 7:43:22 PM (8 years ago)
Author:
sommeria
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  • Tutorial/ParticleImageVelocimetry

    v5 v6  
    2020The vector color indicates the quality of the image correlation maximum leading to each vector, blue is excellent, green average, red poor. The thresholds for such color display can be adjusted from 0 to 1 (perfect image correlation)  in the frame''' [Vectors]''', using the boxes '''[!ColCode1] ''' and '''[!ColCode2]''',  or equivalently by the corresponding  sliders '''[Slider1]''' and '''[Slider2] '''.
    2121
    22 The black color indicates warning in the PIV calculation process. In this example, black vectors are indeed located on the edge, in zones outside the area of flow visualisation (this display can be desactivated by unselecting the box '''hide warn''' (tag '''[CheckHideWarning]''') in the frame '''Vectors''').
     22The black color indicates warning in the PIV calculation process. In this example, black vectors are indeed located on the edge, in zones outside the area of flow visualisation (this display can be desactivated by unselecting the box '''hide warn''' (tag '''[!CheckHideWarning]''') in the frame '''Vectors''').
    2323
    2424The position (x,y) and velocity components (U,V) can be displayed in the upper right text display window by moving the mouse over it. The correlation 'C' and warning flag 'F' are also indicated. The warning flag is equal to 0 for good vectors while non-zero values indicate different cases of calculation problems.
    2525
     26== Histograms ==
     27The global histograms of the vector components  are available in the lower left windows. Histograms limited to a sub-region can be extracted by the menu bar tool '''[Projection object]''', selecting either ['''rectangle]''', '''[ellipse]''' or '''[polygon]''' to define the sub-region (see [wiki:"Tutorial: projection objects" Tutorial: projection objects])
     28
     29== Profiles ==
     30The velocity profile along a line can be obtained by creating a line with the upper menu bar '''[Projection object/line]''', like for image luminosity (see [wiki:"Tutorial: projection objects" Tutorial: projection objects]). Press (and release) the left hand side mouse button, draw the line, and pres it again for the end of the line. The transverse and longitudinal velocity components along this line are then plotted in a new  figure '''view_field'''.
    2631
    2732== Other vector color representations ==
    2833Vector color can also  represent another quantity, as chosen in the menu '''[!ColorScalar] ''' in the frame '''[Vectors]'''. For instance the vector length 'norm(U,V)' can be used. Then a color continuous 64 color code is appropriate, as set in the menu '''[!ColorCode]'''. The color codes values between the valuies set by '''[!MinVec] ''' and '''[!MaxVec].'''
    2934
    30 
    3135== Derived fields ==
    3236
    33 Other field representations are available, selected in the menu '''[Fields]''' at the top of the GUI. For instance the option 'u' provides a (false) color map of the x wise velocity component. A contour plot can be obtained instead of a color map by selecting the option 'contour' in the menu '''[ListContour]''' in the frame''' [Scalar] '''. Then select the contour interval, for instance 0.5. The result is shown in the following figure.  <doc145|center>
     37Other field representations are available, selected in the menu '''[Fields]''' at the top of the GUI. For instance the option 'u' provides a (false) color map of the x wise velocity component. A contour plot can be obtained instead of a color map by selecting the option 'contour' in the menu '''[!ListContour]''' in the frame''' [Scalar] '''. Then select the contour interval, for instance 0.5. The result is shown in the following figure.  <doc145|center>
    3438
    3539To get the vorticity field, 'vort' , and other spatial derivatives, you need to come back to the GUI CIV, select the check boxes '''[FIX1] ''' and  '''[PATCH1] ''' , and press '''[RUN]'''. 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 '''[Fields]'''. The color code can be adjusted by the edit box '''[MinA] ''' (saturated blue color below this value) and '''[MaxA]''' (saturated red color beyond this value).
     
    4044Similarly, the velocity vectors can be superposed to the vorticity field, selecting '''[vort] ''' in '''[Fields_1]''' instead of '''[image '''.
    4145
    42 == Profiles ==
    43 The velocity profile along a line can be obtained by creating a line with the upper menu bar '''[Projection object/line]'''. Then press the left hand side mouse button and draw the line, keeping the button pressed. Release the button to stop the drawing.  The transverse and longitudinal velocity components along this line are then plotted in a new  figure '''view_field'''.
     46== PIV parameters ==
     47Let us run again PIV with Serach x,y=(31,31). Many black vectors are obtained...
    4448
    45 == Histograms ==
    46 The global histograms of the displayed quantities (vector components  or image brightness) are available in the lower left windows. Histograms limited to a sub-region can be extracted by the menu bar tool '''[Projection object]''', selecting either ['''rectangle]''', '''[ellipse]''' or '''[polygon]''' to define the sub-region. Then draw the contour with the mouse, like for line profiles.
     49