Iterative multigrid approach in PIV image processing with discrete window offset
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The features of an improved algorithm for the interrogation of (digital) particle image velocimetry (PIV) pictures are described. The method is based on cross-correlation. It makes use of a translation of the interrogation areas. Such a displacement is predicted and corrected by means of an iterative procedure. In addition, while iterating, the method allows a refinement of the size of the interrogation areas. The quality of the measured vectors is controlled with data validation criteria applied at each intermediate step of the iteration process.
A brief section explains the expected improvements in terms of dynamic range and resolution. The accuracy is assessed analysing images with imposed displacement fields.
The improved cross-correlation algorithm has been applied to the measurement of the turbulent flow past a backward facing step (BFS).
A systematic comparison is presented with Direct Numerical Simulation (DNS) data available on the subject.
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