Posts

Significant speed and memory improvements in PIVlab!

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Mehdi (Manager Mechanical & Aerospace Engineering) from MATHWORKS (the company behind Matlab) approached me a while ago and we discussed how they can support the development of PIVlab. PIVlab seems to be have some importance a relevance to MATHWORKS as it is a pretty popular 3rd party toolbox for Matlab. Together, we identified potential areas in PIVlab that could be improved and MATHWORKS then initiated an internal proposal for programming support. They selected the dutch company Vortech.nl for this project, and Maarten then started to optimize the most important part of PIVlab "PIV_fftmulti.m". He significantly improved the speed of calculations (factor 3), and lowered the memory consumption enormously. This especially helps when processing large images with fine grids, and also makes it possible to benefit from parallel processing of large images. This hasn't been possible before, because at some point RAM was full and the hard disk was used to store temporary dat

New in v2.57: PIVlab Batch Sessions

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 PIVlab can now run in batch mode with the GUI: To prepare a batch session, perform your setup as before (including image loading, calibration, pre- and post processing, but WITHOUT hitting the "Analyze all frames" button ). Then save your session. To perform a batch analysis, you can now enter the following: PIVlab_GUI(1,'c:\folder\my_first_PIVlab_session.mat'); PIVlab_GUI(1,'c:\folder\my_second_PIVlab_session.mat'); PIVlab_GUI(1,'c:\folder\my_third_PIVlab_session.mat'); Where the first number is the number of CPU cores to use (when you have the parallel computing toolbox), and the second argument is the path to your session file. PIVlab will then start, load the session file, perform the analysis, and save the session file in the same folder and with the string '_BATCH' attached to the filename. This allows you to prepare large amounts of image data for analysis, and process them all at once e.g. during the night.

PIVlab is becoming super popular!

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PIVlab seems to become the most cited PIV software of all available PIV softwares (commercial [co] and open source [os]). I performed a search on Google scholar using all PIV software names that I could think of. The per-year-keyword-occurance might be a good indicator for the popularity of a software in academic research.   Steep increase in Keyword occurance for PIVlab (blue)... Seems like this year it will be the  most cited PIV Software in the world ... These are the search terms I used for Google scholar. I wrote a Matlab script that queries Google scholar for these search terms for each year between 2000 and 2021. Google limits the amount of requests per IP, so I had to use a VPN and change the IP frequently: "lavision" AND "davis" AND ("piv" | "particle image velocimetry") ("pivlab" | "piv lab") AND ("piv" | "particle image velocimetry") -"@pivlab.net" "dantec" AND ("dynamic

Very high power pulsed laser diode array prototype :)

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Last week, I have assembled a 20 W pulsed laser diode array for PIV with PIVlab. I just finished the first test and successfully measured velocities in air of up to 20 m/s with a small field of view (47x47 mm) and with the pco.panda 26 DS. The interframe time was 10 microseconds with a pulse length of 10 microseconds. Images with 25 megapixels (= no pixel binning) were captured. As the light intensity is pretty low at these short pulses, pixel binning is recommended however. In water, this will give really awesome results, I will test it the coming week. I was using a third-party laser driver for this test which isn't very good for such short pulses (laser light takes 2 microseconds to ramp up with this driver). So some light will be lost with this third-party driver. With my own circuit, which uses the iC-HGP laser driver chip, this will become much better (only 150 nanoseconds ramp up time). But I'll need to use several of these chips to drive groups of laser diodes because t

High-speed low-cost PIV with the pulsed laserdiode: Examples

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Recently, I asked Prof. de Payrebrune from the University Kaiserslautern / Computational Physics in Engineering if they could lend me their Chronos 1.4 low-cost high-speed camera for some tests. She agreed to support the development of PIVlab which is very cool and kind of her!! Now I did some tests with the camera (captures data at 1.3 megapixels at 1000 Hz) and my new LD-PS pulsed laser diode. The LD-PS has a built-in synchronizer, so it triggers the Chronos and can also do frame-straddling. The Chronos has absolutely brilliant trigger characteristics, as you have complete control over the exposure timing. Now I am not limited to an interframe-time of 1/1000s anymore, but can go down to 10 µs.  When capturing data at 1000 fps, the duty cycle of the illumination becomes quite high. So I added two little fans to the LD-PS housing. Now a duty cycle of up to 50% can be reached without the laser or the driver becoming too hot. The awesome Chronos high-speed camera from krontech.ca Latest

Low-cost PIV, pulsed laser illumination update

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An updated version of my 5W pulsed diode laser module is finished... I changed the PCB and I am now using a dedicated pulsed laser driver chip. There was not really an urgent need to do this, but this chip seemed very sexy. Unfortunately, this is only available as QFN package, but soldering still worked like a charm. Typical PIV application (5 W version): Water: velocities up to 2.5 m/s and illuminated area up to 300 x 200 mm Air: velocities up to 1.5 m/s and illuminated area up to 200 x 150 mm There is raw PIV image data available for you to download here: 1000 µs pulse length, Δ t = 1000 µs, 16 megapixels 50 µs pulse length , Δ t = 200 µs , 16 megapixels 20 µs pulse length , Δ t = 100 µs, 1 megapixel The datasheet is available here .  

Low-cost particle image velocimetry setup: Pulsed laser diode for PIV illumination

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I just finished designing a PIV illumination system that uses one or more laser diodes to generate a thin & bright light sheet. Naturally, this illumination can not compete with e.g. our 200 mJ double-pulsed PIV laser (which costs something between 30 and 40k Euros). But it is very good for illuminating smaller areas (e.g. 300 x 200 mm) and low flow velocities (up to 2.5 m/s). It has a built-in synchronizer for pco cameras, and can be controlled wirelessly from PIVlab. Power consumption is very low, so it can be powered by any standard USB-C phone charger or power bank. PIV products for PIVlab Data sheet

PIV uncertainty: Help and Feedback wanted

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Pretty often, you are asking for a method to quantify the PIV uncertainty. I implemented a method from 2013, and I need your help and feedback to finalize this. It is actually pretty simple, and my code is very straightforward I think. So anyone that had some math in school will be able to help. If you want PIVlab to be improved, then just invest some of your time please. Here is all the information with many images: https://github.com/Shrediquette/PIVlab/issues/58#issuecomment-966591348

PIV like a PRO with PIVlab hardware!

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 This video shows a demo of several PIVlab hardware features and image acquisition features. I developed all of this at Optolution.com , an it is available for sale there too.

Aerodynamics of a hot coffee cup

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 Just for fun:

Free jet with 4 mm diameter: PIV test

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PIVlab's acquisition module can now also control our wireless custom mini seeding generator (all hardware available through OPTOLUTION.com ). That means that a single button click in PIVlab starts the whole measurement. I could add more remote controlled devices to control other hardware via PIVlab too (e.g. start a motor, open a valve, or whatever). Here, I wanted to measure the flow velocity at the exit of the wireless mini seeding generator. Example images can be found below. The field of view in this experiment was about 11 * 9 mm, and the pipe is D6, d4 mm.

PIVlab Paper is out

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 Finally, the new paper that is describing and validating some of PIVlabs new features is out: https://openresearchsoftware.metajnl.com/articles/10.5334/jors.334/

Real-time PIV in PIVlab!

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Today, I quickly tested if I can do real-time particle image velocimetry in PIVlab, and it works :D. Data rate is about 3 Hz, but the code is not optimized yet and running on a core i5 laptop:

PIVlab v2.50 with parallel processing and camera / laser control released! And: New tutorial videos.

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At least for me, this is a great update as processing speed is improved quite a bit, and I can now capture image data and control our laser directly in PIVlab. Sooooo much easier to do experiments for our customers...! With some additional hardware, PIVlab can control a laser and a camera directly. Hardware is available at OPTOLUTION The new PIV acquisition panel - very comfortable and simple. PIVlab-SimpleSync with wireless USB dongle. I also recorded three new tutorial videos for PIVlab: PIVlab tutorial, part 1/3: Quickstart PIVlab tutorial, part 2/3: Pre-processing, analysis and data validation PIVlab tutorial, part 3/3: Data exploration and data export

PIVlab will soon capture images!

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Soon, PIVlab will be more than just a PIV post-processing tool! I am currently implementing some additional features, so that PIVlab can control our laser and the camera directly. I am doing this, because we are using PIVlab for commercial services, and I want to have a PIV setup that is really handy in practice. I also developed a small synchronizer (see picture) that controls our Quantel Evergreen 200 PIV laser and synchronizes it with the ILA5150 PIV.Nano double-image camera. And this synchronizer (which is wireless by the way) is also controlled directly from PIVlab. Everything is as simple as it can get: Press a single button to start camera and laser, images will be saved to your hard disk and directly loaded into PIVlab. Awesome! If you want to have this too for your research, you'll need the PIVlab-SimpleSync ( Optolution.com ), the ILA5150 PIV.Nano camera, and a double-puls laser (e.g. Quantel EVG00070). The PIVlab-SimpleSync wireless synchronizer controls Lamp 1&2, Q

Most downloaded MATLAB toolbox on official Mathworks FileExchange!

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 The amount of active PIVlab users is increasing constantly, and has now made PIVlab the most downloaded toolbox on FileExchange. And among the top 4 Toolboxes, PIVlab is the only one that is not made by a Mathworks employee. Hooray! By the way: I have added some useful features to PIVlab, and I'll record another PIV video tutorial that introduces these additions soon.

Comparison of OpenPIV and PIVlab

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Since quite a while, I benefit from discussions with the main developer of OpenPIV (Prof. Alex Liberzon  from Tel Aviv University) and other people that contribute to OpenPIV. It is almost a bit like a cooperation, as we share thoughts on different topics, and Alex is really into practical and theoretical PIV application. I think we have a very friendly rivalry in developing useful PIV software. The results are available here:  https://github.com/alexlib/openpiv_pivlab_von_Karman_data You will notice that they are very noisy. But we intentionally decided to make the analysis very challenging for our software. The final interrogation area is e.g. only 6*6 pixels, and no smoothing is allowed. I don't really see a difference between OpenPIV and PIVlab, which is probably a good sign. It might be interesting to include commercial software too in this comparison in the future. By the way: Happy New Year to all PIVlab users (and of course all OpenPIV users too ;-D). The year 2020 has been

PIVlab update v2.38

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I made two updates to PIVlab in the last weeks, the latest release is 2.38. The following things were added: Video import functionality: PIVlab can directly work with video files now. Videos are not converted, but frames are directly accessed from the video stream. Vorticity direction was inverted (positive is now ccw) *.png files can be imported now The correlation coefficient is available in the derived parameters panel. It might be used as a measure for the quality of an analysis. I tested several different things, including correlation peak height vs. mean signal strength and ratio of first to second peak. I might make these available later, when I am played around with the data a bit more. Added the PIVlab Quickviewer, an additional GUI that helps to quickly tweak the setup of your experiment while you are recording your images. Image histograms are automatically optimized to get a better display. This can be disabled in "Modify plot appearance" The correlation coefficie

PIVlab is now on GitHub!

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Since quite a while, Matlab File Exchange offers the opportunity to link to a GitHub repository. So I just created a PIVlab repository on GitHub, and changed the Matlab File Exchange site accordingly. I hope that this works out smoothly, and everyone benefits from this change! Here is the link to GitHub: https://github.com/Shrediquette/PIVlab And here is the modified File Exchange site: https://de.mathworks.com/matlabcentral/fileexchange/27659

Please support PIVlab!

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