Single-pixel resolution ensemble correlation for micro-PIV applications
A new correlation method for particle image velocimetry (PIV) is proposed that yields velocity data at single-pixel spatial resolution. This method is an extension of the ensemble correlation method for PIV. This ‘single-pixel ensemble correlation’ method is particularly suited for (quasi-) stationary and periodic flows, which are typically encountered in many micro-PIV applications, such as microfluidics and micro-scale biological flows. The method can yield data at the same level of precision and reliability as conventional PIV data. The main advantage of the new method is that it can resolve steep velocity gradients and obtain unbiased measurements of the velocity in the vicinity of flow boundaries (viz. walls). The performance as a function of the ensemble size is investigated by means of synthetic PIV images. Both ensemble correlation and single-pixel correlation are applied to micro-channel flow. With single-pixel ensemble correlation we obtained a spatial resolution of 300 nm. The results demonstrate that ensemble correlation over-estimates the measured channel width, whereas single-pixel correlation yields a result that is in agreement with the actual channel dimensions.
KeywordsParticle Image Velocimetry Spatial Correlation Particle Image Image Pair Tracer Particle
The authors would like to thank Dr. Christian Poelma for his assistance in programming the single-pixel ensemble correlation method and Dr. Steve Wereley of Purdue University for comments and suggestions with respect to certain parts of the manuscript. This research has been sponsored by the Technology Foundation STW grant DSF.5695 (http://www.stw.nl), and the Foundation for Fundamental Research on Matter (FOM) grant 01ILP011 (http://www.fom.nl).
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