STEREOSCOPIC PARTICLE IMAGE VELOCIMETRY APPLIED TO LIQUID FLOWS

A twin-camera stereoscopic system has been developed to extend convent ional high image-density Particle Image Velocimetry (PIV) to three-dim ensional vectors on planar domains. The stereoscopic velocimeter perfo rms with extremely high accuracy. Translation tests have yielded error s (rms) of 0.2% of full-scale for the in-plane displacement, and 0.8% of full-scale for the out-of-plane component, both of which agree with the errors predicted by an uncertainty analysis. In addition, modifie d techniques in hardware and software have enabled the stereoscopic sy stem to perform successfully when acquiring images through a thick liq uid layer, wherein previously the aberrations arising due to the liqui d-air interface have restricted the use of such systems. With these te chniques, the stereoscopic system, in combination with a simple method for image-shifting, is able to accurately measure three-dimensional v elocity fields in liquids. This is demonstrated by measurements of the helical, three-dimensional flow induced by a rotating disk in glyceri ne.