Parameters

General

filenames
None
navigation pattern
Regular expression patterns for filtering the files in the current directory. Use the back and forward buttons to apply a different filter.
Enable popup warnings
Enable popup warning messages (recommended).
Enable popup info
Enable popup information messages (recommended).
manually select cores
Mannualy select cores. If not seected, all available cores will be used.
number of cores
Select amount of cores to be used for PIV evaluations.
sequence order
Select sequence order for evaluation.
jump
Select sequence order jump for evaluation. Ex: (1+(1+x)),(2+(2+x))
settings for using pandas
Individual settings for loading files using pandas.
skip rows
Number of rows skipped at the beginning of the file.
decimal separator
Decimal separator for floating point numbers.
column separator
Column separator.
read header
Read header. If chosen, first line will be interpreted as the header.Otherwise first line will be replaced with header namesspecified in the text field below.
specify header names
Specify comma separated list of column names.Example: x,y,vx,vy,sig2noise
base output filename
Filename for vector output. A number and an acronym that indicates the process history are added automatically.
delimiter
Delimiter.

Pre-Processing

reference intensity
Define a reference intensity for the plotting of images.

All images are normalized to [0,1] float, preprocessed, and resized to user defined value.

None
invert image
Invert image (see skimage invert()).
subtract background
Subtract background via local sliding windows.
background algorithm
The algorithm used to generate the background which is subtracted from the piv images. Warning: »minA - minB« is still in development, so it may not perform to standard.
starting image
Defining the starting image of the background subtraction.
ending image
Defining the ending image of the background subtraction.
crop region of interest
Crop region of interest. Allows images with different sizes to have a uniform size after cropping.
x min/max
Define left/right side of region of interest by ‘min,max’.
y min/max
Define top/bottom of region of interest by ‘min,max.’
resize intensity
Resize the image intensity to [0,x], where x is a user defined value.

PIV Evaluation

correlation method
Correlation method. Circular is no padding andlinear is zero padding.
subpixel method
Fit function for determining the subpixel position of the correlation peak.
signal2noise calc. method
Calculation method for the signal to noise ratio.
signal to noise mask
the half size of the region around the first correlation peak to ignore for finding the second peak. Only used if sig2noise method = ‘peak2peak’
deformation method
Window deformation method. »symmetric« deforms both first and second images. »second image« deforms the second image only.
interpolation order
Interpolation oder of the spline window deformation. »0« yields zero order nearest interpolation »1« yields first order linear interpolation »2« yields second order quadratic interpolation and so on…
normalize correlation
Normalize correlation.
dt
Interframing time in seconds.
scale
Interframing scaling in pix/m
flip u-component
flip u-component array when saving RAW results.
flip v-component
flip v-component array when saving RAW results.
invert u-component
Invert (negative) u-component when saving RAW results.
invert v-component
Invert (negative) v-component when saving RAW results.
swap A/B files
Swap A/B files when analyzing.
Windowing
None
interrogation window
Size of the final interrogation windows in pixels.
overlap
Size of the final overlap in pixels.
number of passes
Example: A window size of 16 and a number of refinement steps of 3 gives an window size of 64×64 in the fist pass, 32×32 in the second pass and 16×16 pixel in the final pass.
grid refinement
Refine the interregationg grid every PIV pass when performing multipass FFT.
»all passes« refines all passes. »2nd pass on« refines second pass on.
custom windowing
Enable custom windowing for more advanced techniques.
interrogation window
Interrogation window for the first pass.
overlap
Size of the overlap of the first pass in pixels. The overlap will then be calculated for the following passes.
second pass
Enable a second pass in the FFT window deformation evaluation.
interrogation window
Interrogation window for the second pass.
third pass
Enable a third pass in the FFT window deformation evaluation.
interrogation window
Interrogation window for the third pass.
fourth pass
Enable a fourth pass in the FFT window deformation evaluation.
interrogation window
Interrogation window for the fourth pass.
fifth pass
Enable a fifth pass in the FFT window deformation evaluation.
interrogation window
Interrogation window for the fifth pass.
sixth pass
Enable a sixth pass in the FFT window deformation evaluation.
interrogation window
Interrogation window for the sixth pass.
seventh pass
Enable a seventh pass in the FFT window deformation evaluation.
interrogation window
Interrogation window for the seventh pass.
Validation
None
local median validation
Discard vector, if the absolute difference with the local median is greater than the threshold.
local median threshold
Local median absolute difference threshold.
local median kernel
Local median filter kernel size.
global threshold validation
Validate first pass based on set global thresholds.
min u
Minimum U allowable component.
max u
Maximum U allowable component.
min v
Minimum V allowable component.
max v
Maximum V allowable component.
local median validation
Discard vector, if the absolute difference with the local median is greater than the threshold.
local median threshold
Local median absolute difference threshold.
local median kernel
Local median filter kernel size.
standard deviation validation
Remove vectors, if the the sum of the squared vector components is larger than the threshold times the standard deviation of the flow field.
std threshold
Standard deviation threshold.
global threshold validation
Validate first pass based on set global thresholds.
set to first pass
Set the settings of the other pass validations to the same as first pass.
min u
Minimum U allowable component.
max u
Maximum U allowable component.
min v
Minimum V allowable component.
max v
Maximum V allowable component.
PostProcessing
None
replace vectors
Replace vectors between each pass.
replacement method
Each NaN element is replaced by a weighed averageof neighbours. Localmean uses a square kernel, disk a uniform circular kernel, and distance a kernel with a weight that is proportional to the distance.
number of iterations
If there are adjacent NaN elements, iterative replacement is needed.
kernel size
Diameter of the NaN interpolation kernel.
smoothen each pass
Smoothen each pass using openpiv.smoothn.
double first pass strength
Double the smoothing strength on the first pass.
smoothen robust
Activate robust in smoothen (minimizes influence of outlying data).
smoothing strength
Strength of smoothen script. Higher scalar number produces more smoothed data.

Validation

signal to noise ratio validation
Validate the data based on the signal to nose ratio of the cross correlation.
s2n threshold
Threshold for filtering based on signal to noise ratio. Recommended value: between 1.05 and 1.1.
standard deviation validation
Validate the data based on a multiple of the standard deviation.
std threshold
Remove vectors, if the the sum of the squared vector components is larger than the threshold times the standard deviation of the flow field.
local median validation
Validate the data based on a local median threshold.
local median threshold
Discard vector, if the absolute difference with the local median is greater than the threshold.
local median kernel
Local median filter kernel size.
global threshold validation
Validate the data based on set global thresholds.
min u
Minimum U allowable component.
max u
Maximum U allowable component.
min v
Minimum V allowable component.
max v
Maximum V allowable component.

Post-Processing

replace outliers
Replace outliers.
replacement method
Each NaN element is replaced by a weighed averageof neighbours. Localmean uses a square kernel, disk a uniform circular kernel, and distance a kernel with a weight that is proportional to the distance.
number of iterations
If there are adjacent NaN elements, iterative replacement is needed.
kernel size
Diameter of the weighting kernel.
smoothn data
Smoothn data using openpiv.smoothn.
smoothn vectors
Smoothn data with openpiv.smoothn. <each pass> only applies to windef
smoothn robust
Activate robust in smoothn (minimizes influence of outlying data).
smoothning strength
Strength of smoothn script. Higher scalar number produces more smoothned data.
average results (not implemented yet)
Average all results in selected directory. Results in a single file with averaged results.
delimiter
Delimiter.
None
None

Plotting

plot type
Select how to plot velocity data.
diagram title
diagram title.
streamline density
streamline density. Can be one value (e.g. 1) or a couple of values for a range (e.g. 0.5, 1).
streamline direction
Integrate the streamline in forward, backward or both directions. default is both.
x-data
Column name for the u-velocity component. If unknown watch labbook entry.
y-data
Column name for v-velocity component. If unknown watch labbook entry. For histogram only the v-velocity component is needed.
axis scaling
scales the axes. logarithm scaling x-axis –> logx; logarithm scaling y-axis –> logy; logarithm scaling both axes –> loglog.
histogram type
Choose histogram type. Only available for histogramplot.
histogram quantity
The absolute value of the velocity (v) or its x- or y-component (v_x or v_y).
histogram number of bins
Number of bins (bars) in the histogram.
normalize histogram
Normalize histogram (divide by the number of counts, density).
profiles orientation
Plot v_y over x (horizontal) or v_x over y (vertical).
profile density
The amount of profile lines (minimum of 1).
limits for the x-axis
For implementation use (lower_limit, upper_limit).
limits for the y-axis
For implementation use (lower_limit, upper_limit).
Plot
None
vector scaling
Velocity as a fraction of the plot width, e.g.: m/s per plot width. Large values result in shorter vectors.
vector line width
Line width as a fraction of the plot width.
invert y-axis
Define the top left corner as the origin of the vector plot coordinate sytem, as it is common practice in image processing.
Color map
Color map for streamline- and contour-plot.
extend colorbar
Extend the top and bottom of the colorbar to accept out of range values.
set colorbar to:
Set colorbar to velocity components.
number of color levels
Select the number of color levels for contour plot.
min velocity for colormap
minimum velocity for colormap (contour plot).
max velocity for colormap
maximum velocity for colormap (contour plot).
grid
adds a grid to the diagram.
legend
adds a legend to the diagram.