STEP-BY-STEP INSTRUCTION FOR EXAMPLE 3

 

The low-image-density recording samples are from a PIV test in a liquid bridge at a microgravity state. The seeded flow was recorded in a video system at a frame rate of 25 fps.  The measurement was conducted in the cross section of the liquid bridge that has a diameter of 4mm, which is resolved by 450 pixels in the digital image. Detailed description of the experiments and data analysis can be found in papers [1] and [2]. An evaluation procedure is suggested as follows.

 

Step 1: Open a video recording and importing the background image

- Execute file “Edpiv.exe” - The start window is shown on the screen;

- Select menu “File \ Open recording 1” to open “…\ PIVsamples \ 3_LidVideoRecordings \ 5500304.bmp”;

- Select menu “File \ Import B-mask” to import “…\ PIVsamples \ 3_LidVideoRecordings \ background.bmp”.

Step 2: Input imaging scale and time interval

- Click menu “Edit / Scale & time” in the start window to open dialogue box “Imaging scale / time interval”;

- Select radio button mm;

- Input 4 in edit box “Reading on ruler”;

- Input 450 in edit box “Corresponding pixels”;

- Input 20000 in edit box “Time interval [mu-s]”;

- Press “OK” button to return to start window.

Step 3: Subtract background & separate frames

- Press button “Show image” to display the video recording (Recording 1) in the picture frame;

- Press button “Processing” - The “Image processing” window appears;

- Click menu “Edit \ Image operation \ Subtraction” - Dialogue box “Image operation with/to …” appears;

- Choose “Boundary mask”, and then press “OK” button;

- Click menu “Edit \ Frame separation \ Video recording”;

- Answer “Yes” to question “Do you really want to separate this recording into two frames?” - Back to the start window.

Step 4: Set up evaluation parameters

- Click menu “Edit / Evaluation settings” in the start window to open the “Evaluation settings” window;

- Press “HPIT” button and then press button “C” on the right - Dialogue box “HPIT settings” appears;

- Press button “Method 2” and then press button “C” on the right - Dialogue box “Settings for particle position search…” appears;

- Set parameters as
Minimal particle brightness:
40,
Particle image diameter: 6
Select tracer filter: Selected

- Press “OK” to close Dialogue box “Settings for particle position search…”

- Set other parameters in dialogue box “HPIT settings” as
Median filter:
Not selected
Correct position with displacement: Not selected

- Close dialogue box “HPIT settings”

- Set parameters in the “Evaluation settings” window as
Ellipse window: Selected
Boundary mask: Not selected
Recording type: Single recording (pair)
Flow type:
One phase
Initial window shift:
(X,Y), X=0, Y=0
Iteration number:
0 (Initial), 6 (Final) 
Window width :
20 (Initial), 20 (Final)
Window height :
20 (Initial), 20 (Final)
Search radius:
6

- Close “Evaluation settings” window.

Step 5: Evaluate the LID PIV recording pair

- Press button “Evaluation” in the start window - “Evaluation” window is opened;

- Click menu “Start” in “Evaluation” window;

- Answer “Yes” to question “Do you want to start an evaluation?”

- Press button “OK” to close the dialogue box that notices the end of the evaluation.

Step 6: Save evaluation results

- Click menu “File \ Save data” - Dialogue box “Save evaluation results” appears;

- Find a desired folder, type in a file name in the dialogue box;

- Press button “Save” to complete the saving procedure.

Step 7: Plot vector map

- Close EDPIV;

- Use TECPLOT to make plots.

 

 

References:

Shu JZ; Legros JC; Gui LC; Xiong W (1997) The measurement of velocity distribution of liquid bridge at oscillatory state by PIV method, the Joint 10th European and 6th Russian Symposium on Physical Sciences in Microgravity, 15 -20 June, St. Pertersburg, Russia 

Gui L; Merzkirch W; Shu JZ (1997) Evaluation of low image density PIV recordings with the MQD method and application to the flow in a liquid bridge. Journal of Flow Visualization and Image Processing, vol. 4: 333-343