The “Evaluation settings” window is used for selecting evaluation parameters. It can be accessed from start window and “Evaluation” window. Following are descriptions of the parameters.
Method & algorithm - PIV
For standard particle image velocimetry, parameters are determined in “Default settings” window.
Method & algorithm - HPIT
Hybrid particle image tracking. Press button “C” on the right to set parameters as below.
Position search method:
Correct position with displacement - Selected so that the evaluation position is adjusted with particle image displacement.
Method & algorithm - PTV
Particle image tracking velocimetry. Press button “C” on the right to set parameters as below.
Particle image identification:
Single PTV - Selected for tracking only one object in successive frames;
Error detection - Activated for detecting tracking errors with a reversibility check.
Method & algorithm - Ellipse window
Selected to activate an ellipse interrogation window.
Method & algorithm - Boundary mask
Selected to activate the boundary mask, when “B-mask” is imported.
Single recording (pair) - For evaluating a double exposed PIV recording or a single exposed PIV recording pair;
Recording group: individual evaluation - For evaluating a group of PIV recordings and saving individual vector maps (The PIV recordings in the group should be single frames);
Recording group: ensemble evaluation - For evaluating a group of PIV recordings with the average correlation method (The PIV recordings in the group should be single frames).
Single - Single exposed PIV image pair;
Double - Double exposed PIV image.
In case of double exposure, flow direction should be given as
E - East, i.e. directed to the right;
S - South, i.e. directed downwards;
W - West, i.e. directed to the left;
N - North, i.e. directed upwards.
One phase - Single phase flow;
Two phase - Two phase flow;
Continuous - Continuous phase;
Dispersed - Dispersed phase.
Initial window shift
(X,Y) - Interrogation window shifting started with a given value;
M1 - Interrogation window shifting started with valid vectors in memory 1;
M2 - Interrogation window shifting started with valid vectors in memory 2;
SPIV M1&2 button - Pushed down to activate window shift for stereo recording, i.e. M1 for camera A and M2 for camera B. This button is enabled when a stereo PIV recording or a group of stereo PIV recordings are loaded.
Distorted/stereo PIV calibration
None - No calibration;
Grid/vector - Selected to calibrate grid structure before evaluating the stereo or distorted PIV recordings; The displacement vectors will be transferred back to the original evaluation grid and calibrated after evaluation;
Image - Selected to calibrate stereo or distorted PIV recordings before evaluation;
Normal - Selected to use calibration function for normal camera;
A - Selected to use calibration function for stereo camera A;
B - Selected to use calibration function for stereo camera B.
Width - Width of the interrogation grid;
Height - Height of the interrogation grid;
Button “C” on the right is used to activate the changes.
Error limits [pixel]
Dx - Error toleration limit in pixels for horizontal particle image displacement component;
Dy - Error toleration limit in pixels for vertical particle image displacement component.
Multi-pass interrogation setup
The evaluation can be conducted in two iteration steps: initial iteration step and final iteration step.
Iteration number - The sum of the initial iteration number and the final iteration number should be at least 1. The correlation-based tracking algorithm is used in the initial iteration step, and the correlation-based interrogation algorithm is in the final iteration step. To avoid too much evaluation time, the default setup for the initial iteration number is zero.
Window width - Width of the interrogation window;
Window height - Height of the interrogation window;
Search radius - Searching distance in 4 directions in the evaluation function plane. It must be one pixel larger than the maximum of particle image displacements to be determined.
Adaptive interrogation window
N - No window orientation is applied;
Grid - The long axis of the interrogation window is oriented to the direction of larger grid line distance;
Flow - The short axis of the interrogation window is oriented to the direction of larger velocity gradient.
Reshape - Checked to allow change of interrogation window shape during the multi-pass interrogation. When radio button “Grid” is select, the shape of the interrogation window is changed from square (round) to rectangular (Ellipse) shape according to the iteration number. When radio button “Flow” is selected, the shape of the interrogation window is changed from square (round) to rectangular (Ellipse) shape according to the velocity gradient.
Menu - File
Save settings - Used to save current evaluation parameters into a file;
Load settings - Used to import saved evaluation parameters from a file;
Preset 0 - Preset parameters for simple auto-correlation interrogation;
Preset 1 - Preset parameters for normal cross-correlation evaluation;
Close - Used to close “Evaluation settings” window.
Menu - Image filter
N - No image filter applied in evaluation;
SM - Smooth filter with given filter size applied in evaluation;
USM - Unsharp mask with given filter size applied in evaluation;
MPIV - Micro PIV filter with given filter size applied in evaluation;
RN - Regional normalization with given filter size and gray value threshold applied in evaluation;
PF - Particle filter applied in evaluation;
USM2 - Unsharp mask 2 with given filter size applied in evaluation;
Filter w - Width of the digital filter;
Filter h - Height of the digital filter;
Threshold - Gray value threshold for applying the RN filter.
Menu - More
This menu chose is used to open window “Default settings” for parameters that do not need to be changed in most cases.
Window shift & image correction:
Image Correction algorithm:
Range limit validation parameters:
Regular filter validation
Vectors in Evaluation window:
Contours in group - Checked to display contours in Evaluation window, when a group of vector maps is imported.
Data export path
Image transformation method:
Poly - Checked to use polynomial fit method.
Save vectors by pressing ">" or "<" - Selected to save the vector maps in Evaluation window when “>“ and “>“ buttons are pressed.
Edpiv pE 2013 — help