Comparison of Tomo-PIV and 3D-PTV for microfluidic flows

• Published in: Measurement science & technology Vol. 24; no. 2; pp. 24007 - 1-12
• Main Authors: Kim, Hyoungsoo, Westerweel, Jerry, Elsinga, Gerrit E
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.02.2013
• Subjects: Droplets; Flow velocity; flow visualization and imaging; fluidics; image reconstruction; instrumentation and measurement methods in fluid dynamics; liquid thin films; Liquids; micro- and nano-scale flow phenomena; Planes; Three dimensional; tomography; Velocimetry; Velocity measurement; velocity measurements
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/24/2/024007

Two 3D-3C velocimetry techniques for micro-scale measurements are compared: tomographic particle image velocimetry (Tomo-PIV) and 3D particle-tracking velocimetry (3D-PTV). Both methods are applied to experimental data from a confined shear-driven liquid droplet over a moving surface. The droplet has 200 μm height and 2 mm diameter. Micro 3D-PTV and Tomo-PIV are used to obtain the tracer particle distribution and the flow velocity field for the same set of images. It is shown that the reconstructed particle distributions are distinctly different, where Tomo-PIV returns a nearly uniform distribution over the height of the volume, as expected, and PTV reveals a clear peak in the particle distribution near the plane of focus. In Tomo-PIV, however, the reconstructed particle peak intensity decreases in proportion to the distance from the plane of focus. Due to the differences in particle distributions, the measured flow velocities are also different. In particular, we observe Tomo-PIV to be in closer agreement with mass conservation. Furthermore, the random noise level is found to increase with distance to the plane of focus at a higher rate for 3D-PTV as compared to Tomo-PIV. Thus, for a given noise threshold value, the latter method can measure reliably over a thicker volume.