STEP-BY-STEP INSTRUCTION FOR EXAMPLE 1

 

This example shows how to evaluate a double exposed PIV recording with EDPIV software. The image in Case D of PIV Challenge 2001 is used here as a sample recording. It is a double-exposure provided by the research group of Professor Adrian for a near-wall turbulent pip flow experiment. The measurement domain is 6-mm x 6-mm (beginning at the wall) in a 137-mm diameter pipe, and the flow was directed to right. The airflow was seeded with 1-micron olive oil droplets and illuminated with a pulsed YAG laser (~200 mJ/pulse). The particles were imaged with a Nikkor 80-mm f/5.6 Lens and recorded in a 4"x5" photographic film with resolution of 125 lines/mm. The time interval between the laser double pulses is 18 µs. The photographic PIV recording is digitized in size of 1024x1024 pixels. An evaluation procedure is suggested as follows.

 

Step 1: Load PIV recording

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

- Select menu “File \ Open recording 1”;

- Browse hard disks or CDs to find “…\ PIVsamples \ 1_DoubleExposure \ D001_1.bmp”; 

- Select file “D001_1.bmp”, and then press “Open” button.

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”;

- Setup parameters as follows
Image/object ratio:
170667 [pix/m]
Time interval:
18 [mu-s]

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

Step 3: Set up evaluation parameters

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

- Set up parameters as follows
Method & algorithm:
PIV
Ellipse window: Not selected
Recording type:
Single recording (pair)
Exposure type:
Double
Flow direction:
E
Flow type:
One phase
Initial window shift:
(X,Y), X=0, Y=0
Interrogation grid:
16x16
Error limits:
Dx=4.0, Dy=2.0
Iteration number:
0 (Initial), 6 (Final) 
Window width :
64 (Initial), 48 (Final)
Window height :
64 (Initial), 48 (Final)
Search radius:
20

- Click menu “Image filter” to select
Image filter:
USM
Filter : w=
11 , h=11

- Close “Evaluation settings” window.

Step 4: Evaluate the PIV recording

- Press button “Evaluation” in the start window;

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

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

- Wait until the evaluation is completed;

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

Step 5: Save evaluation result

- Click menu “Edit \ Accept results \  valid + corrected” to accept valid and corrected displacement vectors;

- 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 6: Plot vector map

- Close EDPIV;

- Use TECPLOT to make plots.