5 research outputs found
Particle Image Velocimetry Applications Using Fluorescent Dye-Doped Particles
Polystyrene latex sphere particles are widely used to seed flows for velocimetry techniques such as Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV). These particles may be doped with fluorescent dyes such that signals spectrally shifted from the incident laser wavelength may be detected via Laser Induced Fluorescence (LIF). An attractive application of the LIF signal is achieving velocimetry in the presence of strong interference from laser scatter, opening up new research possibilities very near solid surfaces or at liquid/gas interfaces. Additionally, LIF signals can be used to tag different fluid streams to study mixing. While fluorescence-based PIV has been performed by many researchers for particles dispersed in water flows, the current work is among the first in applying the technique to micron-scale particles dispersed in a gas. A key requirement for such an application is addressing potential health hazards from fluorescent dyes; successful doping of Kiton Red 620 (KR620) has enabled the use of this relatively safe dye for fluorescence PIV for the first time. In this paper, basic applications proving the concept of PIV using the LIF signal from KR620-doped particles are exhibited for a free jet and a twophase flow apparatus. Results indicate that while the fluorescence PIV techniques are roughly 2 orders of magnitude weaker than Mie scattering, they provide a viable method for obtaining data in flow regions previously inaccessible via standard PIV. These techniques have the potential to also complement Mie scattering signals, for example in multi-stream and/or multi-phase experiments
Synthesis of Fluorophore-Doped Polystyrene Microspheres: Seed Material for Airflow Sensing
Synthesis of Fluorophore-Doped Polystyrene Microspheres: Seed Material for Airflow Sensing
Kiton red 620 (KR620) doped polystyrene
latex microspheres (PSLs)
were synthesized via soap-free emulsion polymerization to be utilized
as a relatively nontoxic, fluorescent seed material for airflow characterization
experiments. PolyÂ(styrene-<i>co</i>-styrenesulfonate) was
used as the PSL matrix to promote KR620 incorporation. Additionally,
a bicarbonate buffer and polyÂ(diallyldimethylammonium chloride), polyD,
cationic polymer were added to the reaction solution to stabilize
the pH and potentially influence the electrostatic interactions between
the PSLs and dye molecules. A design of experiments (DOE) approach
was used to efficiently investigate the variation of these materials.
Using a 4-factor, 2-level response surface design with a center point,
a series of experiments were performed to determine the dependence
of these factors on particle diameter, diameter size distribution,
fluorescent emission intensity, and KR620 retention. Using statistical
analysis, the factors and factor interactions that most significantly
affect the outputs were identified. These particles enabled velocity
measurements to be made much closer to walls and surfaces than previously.
Based on these results, KR620-doped PSLs may be utilized to simultaneously
measure the velocity and mixing concentration, among other airflow
parameters, in complex flows