Particle Imaging Velocimetry
Particle Imaging Velocimetry
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Project Purpose
The objective of this project is to enhance students’ comprehension of fluid dynamics through the integration of analytical and experimental methods. A Particle Image Velocimetry (PIV) system was developed for the junior-level fluid mechanics laboratory to introduce students to a non-intrusive technique for measuring velocity fields. The chosen experimental case, Taylor–Couette flow, allows for direct comparison between theoretical predictions and experimental results, reinforcing lecture material on flow fields. By providing a hands-on opportunity to calculate Reynolds numbers, radius ratios, and azimuthal velocities before validating them experimentally, this project bridges the gap between classroom theory and laboratory observation, fostering a deeper understanding of fluid behavior.
Technical Process
Technical Process
The PIV system was implemented in two stages. An initial proof-of-concept experiment, shown as Figure 1, used a rectangular acrylic tank with a water medium, neutrally buoyant polyamide seeding particles, a green laser sheet for illumination, and a high-resolution camera for image capture. This setup verified the capability of the selected laser and particles for flow visualization. Images were processed using PIVLab in MATLAB, which tracks particle displacements between frames to determine velocity, and are shown in Figure 2.
Figure 1 Acrylic Tank Experimental Setup (a-laser, b-concaved lens housing, c-acrylic tank, d-laser sheet and seeding particles, e-submersible pump)
Figure 2 First Apparatus Flow Field
Following successful validation, the apparatus was reconfigured into a Taylor–Couette system consisting of a static inner PVC cylinder and a rotating outer acrylic cylinder driven by a belt and DC motor, as shown in Figure 3. The same laser sheet apparatus and polyamide particles were employed, with image capture performed using a Chronos 1.4 high-speed camera. The outer cylinder’s angular velocity was measured via a red tape marker, and experimental conditions were set to maintain laminar flow. Image preprocessing included high-pass filtering and adaptive histogram equalization to improve particle visibility before PIV analysis using a fast Fourier transform window deformation algorithm. A post processed image is shown as Figure 4 for reference.
Figure 3 First Taylor-Couette Experimental Setup (a-laser, b-concaved lens housing, c-laser sheet, d-outer cylinder, e-inner cylinder, f-seeding particles)
Figure 4 Post Processing Image Example
Results
Results
The Taylor–Couette experiment produced a Reynolds number below the turbulence threshold and a well-defined velocity field along the illuminated radial plane. Experimental velocity data were averaged over 100 processed frames and compared to analytical predictions derived from the steady-state Taylor–Couette equations. Approximately 75% of the experimental data exhibited less than 10% error relative to the theoretical values, with deviations primarily occurring near the cylinder walls due to laser sheet reflections and particle tracking loss. The largest observed discrepancy was 74% at the outer wall, while the inner 75% of the domain demonstrated strong agreement with the analytical trend. These results confirm the capability of the apparatus to accurately capture velocity fields in laminar Taylor–Couette flow and highlight areas for improvement in optical alignment and glare reduction.
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