![]() 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. Additionally, LIF signals can be used to tag different fluid streams to study mixing. 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. 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). Polystyrene latex sphere particles are widely used to seed flows for velocimetry techniques such as Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV). Additionally, these particles allow velocity measurements to be made much closer to walls and surfaces than previously. These particles can potentially be used to simultaneously measure the velocity, temperature, and mixing concentration of an airflow. Using statistical analysis, the factors and factor interactions that most significantly affect the outputs were identified. Using a 4-factor, 2-level full factorial 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. A design of experiments (DOE) approach was used to efficiently investigate the variation of these materials. Additionally, a bicarbonate buffer and poly(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. Poly(styrene-co-styrene sulfonate) was used as the PSL matrix to promote KR620 incorporation. Kiton red 620 (KR620) doped polystyrene latex microspheres (PSLs) were synthesized via soap-free emulsion polymerization to be utilized as a relatively non-toxic, fluorescent seed material for airflow characterization experiments. By contrast, Rhodamine (R6G) fluorescent paint provides excellent surface reflection mitigation when paired with the 532 nm filters, producing a signal-to-noise ratio sufficient to allow uniform imaging of particles across the entire calibrated volume. Measurements show that very little incident light is absorbed at white boundaries, producing strong light reflection this effect, in turn: i) saturates the light signal from far-removed suspended particles and ii) greatly reduces the signal-to-noise ratio for particles situated even close to the receiving optics. For each coating, PIV measurementsĪre compared from flow regions that are affected by either direct or indirect reflections. In this study, a comparison of light gathering characteristics ofĪn experimental tomographic PIV system is made using a bluff body model that is coated: i) first, with a commercially available flat white aerosol paint and ii) second, with an airbrushed Rhodamine (R6G) fluorescent paint. Methods for reducing surface reflections during PIV measurements are commonly discussed, but the effects of those surface reflections on PIV measurements are generally neglected.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |