Three-dimensional particle image velocimetry: experimental error analysis of a digital angular stereoscopic system

Abstract

Experimental error analysis of a digital angular stereoscopic PIV system is presented. The paper firstly describes an experimental rig which includes the design of a novel PIV test block for in situ calibration. This allowed the user to set up a static seeded flow volume which was translated in and out of plane to record PIV images using two megapixel CCD cameras positioned for angular stereoscopic viewing. PIV data were collected for a range of camera angles up to and for a range of flow displacements and processed by cross correlation into a set of two-dimensional calibration and flow displacement vectors. These 2D data were then processed into three-dimensional data by the use of geometric and bicubic spline interpolation algorithms and an error analysis performed on the predicted displacements. Results from this analysis have shown optimum system performance will be obtained by using camera angles of between 20 and and f numbers of f16 and higher. The results have also shown a theoretical prediction of system performance derived in previous work, which considers the ratio of out of plane to in plane errors, matches to within 8 and 18% of the experimental system performance.

Particle imaging techniques for volumetric three-component (3D3C) velocity measurements in microfluidics

“…They shifted microscope slides with particles stuck in all three directions and found an uncertainty of B±2 lm for in-plane movements and AE 5l m for the out-of-plane motion. These values are much smaller than the ones expected by the analysis of Lawson and Wu (1997) which match the experimental findings of many other authors that report a larger uncertainty.…”

“…However, in a real system, the calibration is a complex procedure and suffers from distortions and aberrations induced by imperfections of the lens or by refraction between different media (e.g., glass and water of the microchannel). Especially, the small angle between the different views, typically 5-7°, is far from being optimal (C30°, Lawson and Wu (1997)) and introduces errors in the estimation of the out-of-plane component. Giardino et al (2008) made an uncertainty analysis for the determination of the displacement.…”

Three-dimensional flow structures and evolution of the leading-edge vortices on a flapping wing

“…The present asymmetric arrangement is expected to achieve an error ratio <2.5 (Coudert et al, 2000). Following the proposal of Lawson and Wu (Lawson and Wu, 1997a), the aperture of f/16 (f=focal length) was set for both lenses to have a large depth of focus.…”

Support for Advanced Imaging of Premixed Turbulent Combustion Processes

“…The vertical error bars in the figure indicate statistical uncertainty and are proportional to 1/(n) 1 2 , where n is the number of samples in each histogram bin used to construct the distribution. The horizontal error bars are estimated by the rms error given in [4,10] and the uncertainty analysis detailed in [11]. The experimental uncertainty estimates of the SPIV data are based on test results reported in [10].…”

“…The horizontal error bars are estimated by the rms error given in [4,10] and the uncertainty analysis detailed in [11]. The experimental uncertainty estimates of the SPIV data are based on test results reported in [10]. Negative displacement speeds are not entirely unexpected.…”