Fluorescent Particle Image Velocimetry using Atomized Liquid Particles
Abstract
Aerosolized fluorescent particles of Kiton Red 620 dye in a water/glycol fluid are generated using a Venturi-type atomizer and shown to provide effective flow seeding for fluorescent PIV, which can mitigate the detrimental effects of laser reflections from surfaces. 92% of particles by number concentration were found to be < 1 μm in diameter, an acceptable size threshold for gas-flow PIV purposes. A PIV application was conducted in a wind tunnel (freestream velocity U∞ = 27 m/s), using the particles for measurement of the boundary layer flow approaching a forward-facing step (approach boundary layer momentum thickness Reynolds number of Re_θ=5930). Particles were generated from solutions with dye molar concentrations of 2.5×10^(-3) and 1.0×10^(-2) mol/L, and PIV images were obtained for both elastic Mie scattering and filtered, Stokes-shifted fluorescent light. Raw images indicate that the fluorescence yield of the 1.0×10^(-2) mol/L solution provides PIV images with high contrast, even in the near-surface regions where Mie scattering image contrast is highly affected by surface reflections. Boundary layer profiles are processed in the region of adverse pressure gradient leading up to the forward-facing step, where the fluorescent PIV was found to perform comparably to the most optimized Mie scattering PIV; both approaches obtained data as near to the wall as 30 μm, or 2 viscous wall units in our flow of interest. These results indicate that the new seeding method holds promise for near-surface measurement applications with more complicated three-dimensional geometries, where it is impossible to arrange PIV cameras to reject surface-scattered light.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 08, 2022
- Source ID
- 10.1088/1361-6501/ac52c3
Entities
People
- Adit S. Acharya
- K Todd Lowe
- Wing Ng
Organizations
- National Institute of Aerospace
- Office of Naval Research