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.