STEP-BY-STEP INSTRUCTION FOR EXAMPLE 8

This image sample group consists of 156 pairs of low-image-density (LID) PIV recording pairs that are used here to demonstrate how to remove background noise from digital images, how to filter erroneous vectors without a regular evaluation grid, and how to conduct statistical analysis on the base of randomly distributed vectors.

PART 1 - REMOVE BACKGROUND DISTURBANCE

Step 1: Generate raw image file list

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

- Select menu “Edit \ File list” - Dialogue box “Creating file list” appears;

- Press “Input files” button - Dialogue box “Data file list” appears;

- Browse hard drives to find folder “…\ PIVsamples \ 8_LidRecordings\ ”;

- Arbitrarily select one of the Windows Bitmap (BMP) files, and then press “Open” button;

- Press “Output file” button - Dialogue box “Data file list” appears again;

- Browse the hard drives to find an empty folder (or create a new folder);

- Type a name for the file list in the edit box indicated by “File name”, and then click “Save” button;

- Set “Recording type” to 2;

- Press button “Create” to generate the image file list;

- Close the dialogue box to return to the start window.

Step 2: Open raw image group

- Click menu “File \ Image group” - Dialogue box “Recording group” appears;

- Browse the file system to find the image file list created in step 1.

- Click “Open” - The first image of the first pair is shown in the picture frame.

Step 3: Create & remove background image

- Press button “Processing” to open “Image processing” window;

- Click menu “Edit \ Image group \ Average ” - Dialogue box “Settings for image group processing” appears;

- Set up parameters as
Start number:
1
End number:
312

- Press “OK” button and wait until the image processing is completed;

- Click menu “Edit \ Image group \ BG removing \ Object bright ” - Dialogue box “Settings for image group processing” appears;

- Set up parameters as
Start number:
1
End number:
312
File name:
Original
Extension:
“ ”

- Press “OK” button to start image processing;

- Wait until the image processing is completed;

- Close “Image processing” window.

Step 4: Close EDPIV Software

 

(a) Example of raw images

(b) Example of cleared images

 

 

PART 2 - EVALUATE THE LID RECORDING GROUP

Step 1: Generate image file list

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

- Select menu “Edit \ File list” - Dialogue box “Creating file list” appears;

- Press “Input files” button - Dialogue box “Data file list” appears;

- Browse hard drives to find folder that contains the digital images processed in part 1;

- Arbitrarily select one of the image files, and then press “Open” button;

- Press “Output file” button - Dialogue box “Data file list” appears again;

- Browse the hard drives to find a desired destination folder;

- Type a name for the file list in the edit box indicated by “File name”, and then click “Save” button;

- Set “Recording type” to 2;

- Press button “Create” to generate the image file list;

- Close the dialogue box to return to the start window.

Step 2: Open PIV image group

- Click menu “File \ Image group” - Dialogue box “Recording group” appears;

- Browse the file system to find the image file-list created in step 1.

- Click “Open” - The first image of the first pair is shown in the picture frame.

Step 3: Determine 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;

- Determine imaging scale by
Inpu
t 0.26 in edit box “Reading on ruler”
Input
640 in edit box “Corresponding pixels”;

- Setup time interval as 20000 microseconds (mu-s);

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

Step 4: Setup evaluation parameters

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

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

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

- Set parameters as
Minimal particle brightness:
60,
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:
Selected, width=64, height=64
Correct position with displacement: Selected

- Close dialogue box “HPIT settings”

- Set up other parameters in the “Evaluation settings” window as
Ellipse window: Selected
Recording mode:
Recording group: individual evaluation
Flow type:
One phase
Initial window shift:
(X,Y), X=0, Y=-20
Iteration number:
0 (Initial), 6 (Final) 
Window width :
64 (Initial), 32 (Final)
Window height :
64 (Initial), 32 (Final)
Search radius:
24

- Close “Evaluation settings” window.

Step 5: Evaluate PIV recording group

- 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?”

- Set “Start number” and “End number” as 1 and 156, respectively, and press “OK” button in dialogue box “Group evaluation”;

- Wait until the evaluation is completed;

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

- Close “Evaluation window” to return to start window. - Individual velocity vector map files are saved in the same fold that contains the image file list created instep 1.

Step 6: Create vector map file list

- Select menu “Edit \ File list” in the start window - Dialogue box “Creating file list” appears;

- Press “Input files” button - Dialogue box “Data file list” appears;

- Browse hard drives to find folder that contains the velocity vector map files;

- Set “Files of type:” to “Data file [*.dat]”;

- Arbitrarily select one of the velocity vector map files and then press “Open” button;

- Press “Output file” button - Dialogue box “Data file list” appears again;

- Browse the hard drives to find a desired destination folder;

- Type a name for the file list in the edit box indicated by “File name”, and then click “Save” button;

- Press button “Create” to generate the image file list;

- Close the dialogue box to return to the start window.

Step 7: Import vector map file group

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

- Select menu “File \ Load vector map” - Dialogue box “Import evaluation data” appears;

- Set “Files of type:” to “Task files [*.tsk]”;

- Find the vector map data file list created in step 6 and press “Open” button;

Step 8: Filter erroneous vectors

- Click menu “Tools \ Filtering” - Dialogue box “Irregular median filter for vectors” appears;

- Setup parameters as
Filter window:
Width=64, Hight=64
Limits for error detection:
dx=10, dy=20

- Press button “OK” in the dialogue box.

Step 9: Statistically analyze the valid vectors

- Click menu “Tools \ Statistics” and set parameters in dialogue box “Vector-map/image number” as
Start number:
1
End number:
156

- Press “OK” button;

- Set parameters in dialogue box “Irregular statistical analysis” as
Width=
64,
Height=
64,
X-step=
16,
Y-step=
16,
and press “OK” button.  

Step 10: Export statistical 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 11: Plot vector map

- Close EDPIV;

- Use TECPLOT to make plots.