STEP-BY-STEP INSTRUCTION FOR EXAMPLR A

 

This section provides examples of using EDPIV to calibrate a stereo PIV system and to evaluate stereo PIV recordings. The calibration target images and stereo PIV recordings are synthetically created by using simulation tools in EDPIV.

 

PART 1 - DETERMINE CALIBRATION FUNCTIONS

Step 1: Start EDPIV software and load calibration target images

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

- Click menu “File \ Open recording 1” to load image “…\ PIVsamples \ a_StereoRecordings \ TargetGrid \ Camera_A_000.bmp”;

- Click menu “File \ Open recording 2” to load image “…\ PIVsamples \ a_StereoRecordings \ TargetGrid \ Camera_B_000.bmp”;

Step 2: Determine calibration marker search pattern

- Press button “Evaluation” to open “Evaluation window”;

- Press button Gto hide evaluation grid lines;

- Press button Pto hide evaluation points;

- Press button “Image” to display recording 1 as background image - Blue text “Reco.1” is shown on the top left corner of the window;

- Increase window size to clearly see details of the target grid (i.e. 11 vertical & 11 horizontal lines);  

- Select menu “Tools \ Calibration markers \ Image pattern”;

- Move the mouse arrow to include the intersection of the 2nd vertical and 2nd horizontal (from bottom and left) calibration grid lines in the square frame, and the press left mouse button - dialogue box “Image pattern for calibration marker search” appears;

- Set parameters as
IPT settings:
synthetic image pattern
W width [pix]:
32
S radius [pix]: 12
Shape: button “+” pushed down
Intensity: 
button “P” pushed down
Size variation [%]:
H=0.25, V=0.25, O=0.25
Angles [deg]:
H=0, V=0, O=0
and then press button “C”;

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

Step 3: Determine positions of calibration markers for the left camera

- Select menu “Edit \ Grid structure \ Irregular” to activate the irregular grid function;

- Point mouse arrow at the intersection of the 2nd vertical and 2nd horizontal (from bottom and left) calibration grid lines and press left mouse button - Dialogue box “Irregular grid” appears;

- Select radio button on the bottom-left corner of the dialogue box;

- Determine other three corners of the irregular grid in the same way as
Intersection of
10th vertical and 2nd horizontal lines for bottom-right ratio button,
Intersection of
2nd vertical and 10th horizontal lines for top-left radio button,
Intersection of
10th vertical and 10th horizontal lines for top-right radio button;

- Point mouse arrow at the center portion of the image and press left mouse button - Dialogue box “Irregular grid” appears;

- Input grid column number 9 in the left edit box and row number 9 in the right edit box, respectively;

- Press “Create” button in the dialogue box - An irregular grid structure is created;

- Use column shifting function activated by menu choice “Edit \ Grid/point shift \ Column” to better match the irregular grid to the target grid;

- Press “TJ” button to disable the mouse function;

- Select menu dialogue “Tools \ Calibration markers \ Group distribution” - Dialogue box “Calibration marker distribution” appears;

- Input parameters for the objective plane as: X0=10, Y0=10, X1=90, Y1=90;

- Press “OK” button to close the dialogue box;

- Click menu “Tools \ Calibration markers \ Group search” to search for grid markers (intersection points of grid lines) near to the points of the irregular grid - Dialogue box “Add/edit calibration markers” appears;

- Delete points where the search is not successful;

- Close the dialogue box.

Step 4: Create image calibration function for the left camera

- Select menu “Tools \ Calibration function \ Create function” - Dialogue box “PIV cameras” appears;

- Select “A” and press button “OK”;

- Press “OK” to close the information box with message “The calibration function is ready!”

- Select menu “Tools \ Calibration function \ Image effect” - Dialogue box “Distorted image calibration” appears;

- Setup parameters in dialogue box “Distorted image calibration” as
Coordinate limits [mm]: Xmin=0, Xmax=100, Ymin=0, Ymax=100;
Calibrated image frame:
same
Stereo camera:
A;

- Press “OK” button - A calibrated grid image is displayed in the window.

Step 5: Determine positions of calibration markers for the right camera

- Press button “image” to display the target grid image of camera B (Reco. 2) as background image in the window;

- Select menu “Tools \ Calibration markers \ View & edit” - Dialogue box “Add/edit calibration markers” appears;

- Press button “Clear” to remove calibration marker data for camera A, and then close the dialogue box;

- Determine calibration marker positions as in Step 3.

Step 6: Create image calibration function for the right camera

- Select menu “Tools \ Calibration function \ Create function” - Dialogue box “PIV cameras” appears;

- Select “B” and press button “OK”;

- Press “OK” to close the information box with message “The calibration function is ready!” - (If the calibration function cannot be determined, select menu “Tools \ Calibration markers \ View & edit” to delete a few markers and try again.)

- Select menu “Tools \ Calibration function \ Image effect” - Dialogue box “Distorted image calibration” appears;

- Setup parameters in dialogue box “Distorted image calibration” as
Coordinate limits [mm]: Xmin=0, Xmax=100, Ymin=0, Ymax=100;
Calibrated image frame:
same
Stereo camera:
B;

- Press “OK” button - A calibrated grid image is displayed in the window.

Step 7: Save image calibration functions

- Select menu “Edit \ Stereo system” - Dialogue box “Stereo/distorted PIV recording” appears;

- Press button “Write” - Dialogue box “Export SPIV system data” appears;

- Find a desired destination folder, input a file name, e.g. “system01.dat”, and then press “Save” button;

- Answer “Yes” to question “Do you want to save data in the selected file?”

- Close dialogue box “Stereo/distorted PIV recording”;

- Close EDPIV.

 

 

PART 2 - CALIBRATE STEREO SYSTEM

Step 1: Load shifted target images for camera A

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

- Click menu “File \ Open recording 1” to load image “…\ PIVsamples \ a_StereoRecordings \  TargetGrid \ Camera_A_N50.bmp”;

- Click menu “File \ Open recording 2” to load image “…\ PIVsamples \ a_StereoRecordings \ TargetGrid \ Camera_A_P50.bmp”;

- Click menu “File \ Import B-mask” to load image “…\ PIVsamples \ a_StereoRecordings \ TargetGrid \ Camera_A_000.bmp”.

Step 2: Import calibration functions

- Select menu “Edit \ Stereo system” - Dialogue box “Stereo/distorted PIV recording” appears;

- Press button “Read” - Dialogue box “Import SPIV data” appears;

- Browse hard file system to find the file created in Part 1, Step 7, e.g. “system01.dat”, and press “Open” button;

- Answer “Yes” to question “Do you want to read data from the selected file?”

- Close dialogue box “Stereo/distorted PIV recording”.

Step 3 Calibrate the image pair and select evaluation points

- Press button “Evaluation” to open “Evaluation” window;

- Increase window size to clearly see the target lines;

- Select menu “Tools \ Calibration \ Image pair” - Dialogue box “Distorted image calibration” appears;

- Setup parameters in dialogue box “Distorted image calibration” as
Coordinate limits [mm]: Xmin=0, Xmax=100, Ymin=0, Ymax=100
Calibrated image frame:
same
Stereo camera:
A;

- Press “OK” button - The calibrated image of the target grid without shift (Mask B) is displayed in the window;

- Select menu “Tools \ Calibration markers \ Image pattern”;

- Move image pattern selecting frame to include an intersection of target grid lines and then press left mouse button - dialogue box “Image pattern for calibration marker search” appears;

- Set parameters as
IPT settings:
synthetic image pattern
W width [pix]:
32
S radius [pix]: 12
Shape: button “+” pushed down
Intensity: 
button “P” pushed down
Size variation [%]:
H=0.25, V=0.25, O=0.25
and then press button “C”;

- Press “OK” button to complete image pattern selection;

- Select menu “Edit \ No grid distribution \ Marker” and answer “No” to question “Do you want to keep current evaluation point?”

- Add as many as possible evaluation points to the target line intersections;

- Press “TJ” button to inactivate the arbitrary evaluation point function.

Step 4: Setup evaluation parameters

- Click menu “Edit / Evaluation settings” in “Evaluation” window;

- Setup parameters as follows
Method & algorithm:
PIV
Ellipse window: Selected
Boundary mask:
Not selected
Recording type:
Single recording (pair)
Exposure type:
Single
Flow type:
One phase
Initial window shift:
X=0, Y=0
Distorted/stereo PIV calibration:
No calibration
Interrogation grid:
Ignored
Error limits:
Ignored
Iteration number:
0 (Initial), 6 (Final)
Window width:
64 (Initial), 32 (Final)
Window height:
64 (Initial), 32 (Final)
Search radius:
20

- Close “Evaluation settings” window.

Step 5: Determine displacements of the target grid

- 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;

- Delete erroneous vectors with the right mouse function.

Step 6: Calibrate system setup for camera A

- Click menu “Tools \ Calibration \ Stereo system” in “Evaluation” window - Dialogue box “Stereo PIV system calibration” appears;

- Setup parameters as
Camera:
A
Out-of-plane displacement:
1 mm

- Press button “Calibration” to conduct the calibration;

- Press “Update” button in dialogue box “Stereo system calibration” and the press “OK” button;

- Close “Evaluation” window.

Step 7: Load shifted target images for camera B

- Click menu “File \ Open recording 1” to load image “…\ PIVsamples \ a_StereoRecordings \ TargetGrid \ Camera_B_N50.bmp”;

- Click menu “File \ Open recording 2” to load image “…\ PIVsamples \ a_StereoRecordings \ TargetGrid \ Camera_B_P50.bmp”;

- Click menu “File \ Import B-mask” to load image “…\ PIVsamples \ a_StereoRecordings \ TargetGrid \ Camera_B_000.bmp”.

Step 8: Calibrate the image pair and select evaluation points

- Press button “Evaluation” to open “Evaluation” window;

- Increase window size to clearly see the target lines;

- Select menu “Tools \ Calibration \ Image pair” - Dialogue box “Distorted image calibration” appears;

- Setup parameters in dialogue box “Distorted image calibration” as
Coordinate limits [mm]: Xmin=0, Xmax=100, Ymin=0, Ymax=100
Calibrated image frame:
same
Stereo camera:
B;

- Press “OK” button - The calibrated image of the target grid without shift is displayed in the window;

- Click menu “Edit \ Clear all” and answer “Yes” to question “…Do you want to proceed?” 

Step 9: Determine displacements of the target grid

- 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;

- Delete erroneous vectors with the right mouse function.

Step 10: Calibrate system setup of camera B

- Click menu “Tools \ Calibration \ Stereo system” in “Evaluation” window - Dialogue box “Stereo PIV system calibration” appears;

- Setup parameters as
Camera:
B
Out-of-plane displacement:
1 mm

- Press button “Calibration” to conduct the calibration;

- Press “Update” button in dialogue box “Stereo system calibration” and the press “OK” button;

- Close “Evaluation” window.

Step 11: Save system calibration data

- Select menu “Edit \ Stereo system” - Dialogue box “Stereo/distorted PIV recording” appears;

- Press button “Write” - Dialogue box “Export SPIV system data” appears;

- Find a desired destination folder, input a file name, e.g. “system02.dat”, and then press “Save” button;

- Answer “Yes” to question “Do you want to save data in the selected file?”

- Close dialogue box “Stereo/distorted PIV recording”;

- Close EDPIV.

 

 

PART 3 - EVALUATE A SINGLE SPIV RECORDING

Step 1: Load a stereo PIV recording

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

- Click menu “File \ Open recording 1” to load image “…\ PIVsamples \ a_StereoRecordings \ Recording_single \ a_01.bmp”;

- Click menu “File \ Open recording 2” to load image “…\ PIVsamples \ a_StereoRecordings \ Recording_single \ a_02.bmp”;

- Click menu “File \ Import mask 1” to load image “…\ PIVsamples \ a_StereoRecordings \ Recording_single \ b_01.bmp”;

- Click menu “File \ Import mask 2” to load image “…\ PIVsamples \ a_StereoRecordings \ Recording_single \ b_02.bmp”;

- Select menu “Edit \ Stereo system” - Dialogue box “Stereo/distorted PIV recording” appears;

- Press “Add” button;

Step 2: Import calibration functions and system data

- Press button “Read” in dialogue box “Stereo/distorted PIV recording”- Dialogue box “Import SPIV data” appears;

- Browse hard file system to find the file created in Part 2, Step 11, e.g. “system02.dat”, and press “Open” button;

- Answer “Yes” to question “Do you want to read data from the selected file?”

- Close dialogue box “Stereo/distorted PIV recording”;

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”;

- 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 “Evaluation” window;

- Setup parameters as follows
Method & algorithm:
PIV
Ellipse window: Selected
Recording type:
Single recording (pair)
Exposure type:
Single
Flow type:
One phase
Initial window shift:
X=0, Y=0
Distorted/stereo PIV calibration:
Grid/vector (or Image), Normal
Interrogation grid:
16x16
Error limits:
Dx=3, Dy=3
Iteration number:
0 (Initial), 6 (Final)
Window width:
64 (Initial), 32 (Final)
Window height:
64 (Initial), 32 (Final)
Search radius:
20

- Close “Evaluation settings” window.

Step 5: Evaluate the SPIV recording

- 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?”;

- Wait about 1.5 minutes (P-4 2.5GHz) until the evaluation is completed;

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

Step 6: Save evaluation result

- 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.

 

 

PART 4 - EVALUATE A GROUP OF SPIV RECORDINGS

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 “…\ PIVsamples \ a_StereoRecordings \  Recording_group”;

- Arbitrarily select one of the Windows Bitmap (BMP) files;

- Press “Open” button - Dialogue box “Data file list” is closed;

- 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”;

- Click “Save” button - Dialogue box “Data file list” is closed;

- Set “Recording type” to 5;

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

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

Step 2: Opening the SPIV recording group

- Click menu “File \ Image group” in the start window - 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: Import calibration functions and system data

- Select menu “Edit \ Stereo system” - Dialogue box “Stereo/distorted PIV recording” appears;

- Press button “Read” - Dialogue box “Import SPIV data” appears;

- Browse hard file system to find the file created in Part 2, Step 12, e.g. “system02.dat”, and press “Open” button;

- Answer “Yes” to question “Do you want to read data from the selected file?”

- Close dialogue box “Stereo/distorted PIV recording”.

Step 4: Determine imaging scale and time interval

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

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

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

Step 5: Setup evaluation parameters

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

- Setup parameters as follows
Method & algorithm:
PIV
Ellipse window: Selected
Recording type:
Recording group: individual evaluation
Exposure type:
Single
Flow type:
One phase
Initial window shift:
X=0, Y=0
Distorted/stereo PIV calibration:
Image
Interrogation grid size:
16x16
Error limits:
Dx=3, Dy=3
Iteration number:
0 (Initial), 6 (Final)
Window width:
64 (Initial), 32 (Final)
Window height:
64 (Initial), 32 (Final)
Search radius:
20

- Close “Evaluation settings” window.

Step 6: Evaluate the SPIV recordings

- 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?”

- Determine start number and end number in dialogue box “Group evaluation “ and press “OK” button;

- Wait about 15 minutes (P-4 2.5GHz) until the evaluation is completed;

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

- Close EDPIV;

 

Tecplot data files are saved in the folder that contains the image file list.

 

Mean velocity map: