Abstract
By using standard particle image velocimetry algorithms the interrogation windows are placed on a structured grid and the spatial resolution is manually chosen. Clearly, a better approach is to choose automatically the processing parameters and to adapt them locally both to the seeding density and flow conditions. An adaptive space resolution method is introduced herein and the performance assessment performed by using both synthetic and real images clearly shows the advantages of the technique.
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Abbreviations
- IDM:
-
Image deformation method
- MTF:
-
Modulation transfer function
- PIV:
-
Particle image velocimetry
- WW:
-
Weighting window
- a :
-
Modulation factor associated to the correlation step of the algorithm, dimensionless
- b :
-
Modulation factor associated to the weighted average step of the algorithm, dimensionless
- c :
-
Modulation factor associated to the dense predictor step of the algorithm, dimensionless
- k :
-
Iteration number, dimensionless
- m k :
-
Modulation factor at iteration k, dimensionless
- m ks,kf :
-
Combined modulation factor, dimensionless
- N :
-
Number of samples, dimensionless
- p :
-
Percentage of particles lost between the images, dimensionless
- r :
-
Maximum value of the correlation coefficient map, dimensionless
- r c :
-
Corrector displacement field, pixels
- r p :
-
Dense predictor displacement field, pixels
- r k :
-
Displacement field at iteration k, pixels
- \( \overline{{{\user2{r}}_{p}^{k - 1} }} \) :
-
Weighted average of the dense predictor displacement field, pixels
- u :
-
Horizontal displacement, pixels
- \( \bar{u} \) :
-
Mean, over the interrogation window, horizontal displacement, pixels
- v :
-
Vertical displacement, pixels
- W a :
-
Interrogation window linear dimension, pixels
- W b :
-
Linear dimension of the weighting window used in the weighted average step of the algorithm, pixels
- W bo :
-
Optimal linear dimension of the weighting window used in the weighted average step of the algorithm, pixels
- x :
-
Horizontal image coordinate, pixels
- y :
-
Vertical image coordinate, pixels
- δ :
-
Total error, pixels
- δ a :
-
Weighted average of the total error (all wavelengths), pixels
- δ l :
-
Weighted average of the total error (larger wavelengths), pixels
- ζ :
-
Adaptive parameter, \( r{\sqrt[4]{\sigma}} \)
- λ :
-
Spatial wavelength, pixels
- σ :
-
Standard deviation of the even local part, pixels
- Θ:
-
Standard deviation of the vorticity, dimensionless
- s :
-
Starting phase
- f :
-
Final phase
References
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Astarita, T. Adaptive space resolution for PIV. Exp Fluids 46, 1115–1123 (2009). https://doi.org/10.1007/s00348-009-0618-5
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DOI: https://doi.org/10.1007/s00348-009-0618-5