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Category Archives: urapiv

This blog does not allow to upload large video clips and we now use the service of Google video to show you some of the experimental set-ups, systems and measurements we’ve done.

The first in the line is our invention, XPIV - mutliplane stereoscopic particle image velocimetry system. As you will see in a minute, it is very simple, easily extendable from your standard stereoscopic PIV system and the only missing ingredients are a) high-energy cubic beamsplitters, b) rotational mount with a half-wave plate, c) some sophisticated image processing and d) know-how. The last two components are kept with us, but we’re open for cooperation and look for the new challenges. The rest costs less than 1000 USD and it’s all on-shelf products. Highly recommended.

Historical view of a PIV system (taken from Tecplot)

and of PIV post-processing:

Time is different nowadays…. wait and see …

urapiv_logo.png

Hi to all the Insight 3G users (for incompetent ones, Insight 3G [PDF] is a new software from TSI Inc that tries to compete for a long time with URAPIV :-)). The software is great, as we can see from the latest evaluation copy we work with, but it lacks one small thing - import of images from other sources rather than acquiried directly with Insight 3G. It means that one has to rename the files to let Insight understand that these are the pair of images to correlate. I do not know if it is the same with other software packages, but let’s be proud to tell that URAPIV works with all image formats (really thanks to Mathworks IMREAD) but also does not care about the naming convention: a/b or b/c or 1,2,3, … or whatever. It goes to the directory, looks into and decides which convention is used. Simple.
However, for those who’re “stacked” with Insight 3G and cannot move to URAPIV (:-)), can use one of the two scripts below to rename in more or less automatic way the images taken by a high speed camera, named 1,2,3,… and make them usable for Insight (put the renamed files into RawData subdirectory of your experiment)

In Python:

## Copyright (C) 2006 Alex Liberzon
##
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are
## met:
##
##  1. Redistributions of source code must retain the above copyright
##     notice, this list of conditions and the following disclaimer.
##  2. Redistributions in binary form must reproduce the above copyright
##     notice, this list of conditions and the following disclaimer in
##     the documentation and/or other materials provided with the
##     distribution.
##
## THIS SOFTWARE IS PROVIDED BY THE AUTHOR “AS IS” AND ANY EXPRESS OR
## IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
## WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
## DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
## INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
## (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
## SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
## HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
## STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
## IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
## POSSIBILITY OF SUCH DAMAGE.
 
#!/usr/bin/env python

“”" Python script that copies the successive TIFF files in the current directory in pairs of a
straddle form for the INSIGHT 3G software (by TSI Inc.): A,B with a user selected JUMP factor between the frames. New set of TIFF files is
generated in the same directory. “”"

import glob
import shutil

jump = input(”Please enter a jump: “)
d=glob.glob(’*.tif’)

for k in range(1,len(d)-jump):
  src = d[k-1]
  des = ‘RUN%06d.T000.D000.P000.H000.LA.TIF’ % k
  shutil.copyfile(src,des)
  src = d[k+jump-1]
  des = ‘RUN%06d.T000.D000.P000.H000.LB.TIF’ % k
  shutil.copyfile(src,des)

In Matlab:

function rename_TIFF_Insight3G(jump);

% Matlab function that copies the successive TIFF files in the current directory in pairs of a
%straddle form for the INSIGHT 3G software (by TSI Inc.): A,B with a user selected JUMP factor between the % frames. 
% A new set of TIFF files is generated in the same directory.

if ~nargin, jump = 15, end

d = dir(’*.tif’);

k = 0;
for i = 1:length(d)-jump
    k = k + 1;
    dos(['copy ',d(i).name,' ',sprintf('Run%06d.T000.D000.P000.H001.LA.tif',k)]);
    dos(['copy ',d(i+jump).name,' ',sprintf('Run%06d.T000.D000.P000.H001.LB.tif',k)]);
end

Of course it is very simple approach and should be really well developed, but TSI will probably develop a new version that will overcome this small difficulty. By that time, URAPIV will be anyhow much better.

The story started from one e-mail:

I would like PIV to evaluate some of my video data. In search of a solution, I have found your tool, URAPIV. I have downloaded URAPIV_GUI_TIFF (Release Date September 20, 2004) from sourceforge.net.Unfortunately, I am running into a few problems. First, I am only able to read in 4 images at a time. In addition, the code only seems to work if the images that are included with the URAPIV_GUI_TIFF download are included in the directory containing the images that I would like to analyze.

Do you have any ideas on how to have the software read in all of the images? Also, is there a manual for this software?

Many thanks and best greetings.

Jeremiah Williams

So, we answered (as usual), suggesting to take a first look at the images and to reproduce the problem (that sometimes happen simply due to Matlab version, compatability issues, etc.) and got a sample of 10 frame AVI file. Since it was not our first time to get the AVI files, we decided to take a step and slightly adopted the URAPIV code for reading and working with AVI files. The technical details are in the Tutorial. Here we’d like to tell you the story behind the images. Our users come from the well known (in plasma physics and beyond it) lab from Auburn University:


Particularly, we have found the old-dated pages about PIV analysis in dusty (or complex) plasma, e.g.

The lab knows about 2D PIV for a long time, as one can see from the short intro to PIV on their web site:

And it’s an honour for the URAPIV project to be helpful in this research. The output of our short customized solution is an updated URAPIV_AVI version (that’s recently has been uploaded to the sourceforge.net) and the example looks like:

result.png

Read more about the technical stuff on the Tutorial page.

The proper credit should be as the author says:

The video comes from the Colloidal (Dusty) Plasmas research group at the Institute of Physics, University Greifswald, Germany. The video was shot by Matthias Wolter, who has been visiting our lab for the past couple of months, during the 8th DLR parabolic flight campaign. In the video, a plasma crystal under microgravity conditions was manipulated by a 600 mW laser.
You can find additional information on the type of work that he does at his groups web page (http://www5.physik.uni-greifswald.de/).
The PIV aspect of this work comes from work done at our group, the Plasma Sciences Laboratory at Auburn University. We have applied PIV techniques to the study of complex (dusty) plasmas for a number of years and have two commercial PIV systems (a 2D system from TSI and a stereo system from LaVision). Additional information on this can be found at our group’s web page, http://narn.physics.auburn.edu.

With kind regards,
Jeremiah Williams

As Python has been updated for 2.4, Scipy to 0.5.0 and Numpy moves towards 1.0 release, we follow it closely and update the PyPIV (that works with Python 2.3, Scipy 0.3) to PyPIV.2.4.py. Download link.
We thank our new developer, Dwishen Ramanah for the update.
Use the Sourceforge.net to download a new version. It’s highly recommended to use binary release of Enthought for Python 2.4 with Scipy/Numpy to sovle all the headache of the installations. Our Linux/Unix/Mac users should follow the installation instructions on the Scipy website.

Dear URAPIV users, we’re glad to announce a new, updated version of URAPIV with graphical user interface (GUI), reading TIFF images from the high-speed cameras (high frame rate PIV applications oriented). The main update is a new GUI for image selection and a new parameter (which is very useful for this type of applications) - JUMP. Yes, it is a jump in terms of \Delta t between the images. The user may process every pair of the files (1 with 2, 2 with 3, …) or of pairs at every possible time separation (e.g., 1 with 5, 2 with 6 means jump = 5). Please, go to Sourceforge.net and download the most recent version.

Developed and tested on Windows XP with Matlab 7SP3 (R14SP3). Not tested on R2006a. We work on the tutorial (click the thumbnail below to see the full-size snapshot). Thanks for your patience.

This is a quest for URAPIV users:

If one takes an air jet image like the following one (but twice) and apply URAPIV (with a click of a mouse)

then the result is:

 

True or not?

(hint: colors and view of the arrows in the vector field)

I just found some old publication that people from soil mechanics wrote about their way of using URAPIV [link to PDF file]