A triple-exposure color PIV technique for pressure reconstruction

The study developed a triple-exposure color particle image velocimetry (TE-CPIV) technique associated with pressure reconstruction, and validated its feasibility. A light source with the three primary colors of red, green, and blue (R, G, and B) is produced in a time sequence by a liquid crystal display (LCD) projector. Particle images at three different instants under the color illuminations are captured in one snapshot using a color digital single-lens reflex (SLR) camera with a complementary metal-oxide semiconductor (CMOS) sensor. A contamination correction algorithm based on a specific calibration is performed on the different color layers (R layer, G layer, and B layer) of the raw color image to reduce the contaminated intensity of each color illumination on the other two color layers. The corrected intensity generates three new color layers, from which a standard cross-correlation process in the classical PIV method is used to obtain two velocity fields. Eventually, an instantaneous pressure field is reconstructed from the two velocity fields. The feasibility of TE-CPIV was tested by two experiments with a solid body rotation flow and a cylinder wake flow. The results show acceptable accuracy and robustness of the new technique. The idea of the TE-CPIV is believed to provide a simple and effective way of estimating a pressure field with low cost and high convenience.