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

Abstract

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.

Spontaneous Marangoni Mixing of Miscible Liquids at a Liquid–Liquid–Air Contact Line

“…Hence, we remove these outliers by applying a mask filter based on the measurement images. 25 The whole pre-and post-processing procedures are performed by using Matlab.…”

Experimental and theoretical study of dewetting corner flow

“…Furthermore, tomographic PIV is able to reconstruct the liquid-air interface, and hence it is possible to apply the velocity measurement to a flow domain with a free surface (Kim, Westerweel & Elsinga 2013). Figure 4 shows the experimental set-up for the volumetric flow measurement.…”

“…For the given optical parameters we have z 0 ≈ 120 µm. The accuracy of the present experimental system is evaluated in preceding studies (Kim et al 2011(Kim et al , 2013. The error amplitude of the particle displacement that is related to the divergence root-mean-square (r.m.s.)…”

“…The spatial discretization is 250 voxels mm −1 . The PIV experimental details are described in detail by Kim et al (2011Kim et al ( , 2013.…”

Holographic astigmatic particle tracking velocimetry (HAPTV)

“…In comparison, three-dimensional (3D) flow field imaging techniques such as 3D particle image/tracking velocimetry (PIV/PTV) [6,7], commonly used in the lab settings, can yield unprecedented information for fundamental understanding of many important physical processes in the atmosphere and ocean. Although multi-camera 3D PIV/PTV techniques such as tomographic PIV [8][9][10] and synthetic aperture PTV [11] are more common, several singlecamera 3D PTV techniques using plenoptic [12,13], defocusing [14][15][16], and holographic [17][18][19][20] imaging approaches have been gaining popularity for velocity measurement due to their simple setup and minimal calibration requirements [14,[21][22][23][24]. Such advantages allow these techniques to be applied underwater and reduce the intrusiveness to the measurement volume, which is crucial for in situ applications.…”