Quantification of dispersed phase concentration using light sheet imaging methods |
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Authors: | Philip?L?Knowles Email author" target="_blank">Ken?T?KigerEmail author |
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Institution: | (1) Applied Aerodynamics & Store Separation Branch, NAVAIR, Patuxent River, MD, USA;(2) Department of Mechanical Engineering, University of Maryland, College Park, MD, USA |
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Abstract: | With the prevalence of particle image velocimetry (PIV) as a quantitative tool for fluid mechanics diagnostics, its application
for analyzing complicated multiphase flows has been steadily increasing over the last several decades. While the primary issue
in using PIV for multiphase flows is in separating the information of the phases for independent analysis with a minimum of
spurious “cross-talk,” an equally crucial but often overlooked point is in the accurate quantitative measurement of the dispersed
phase concentration. Accurate concentration measurement is important due to the fact that the dispersed phase is often heterogeneously
distributed in both space and time, either due to a non-uniformity of the source of particulates (such as a spray nozzle or
sediment boundary) or due to inertial migration of the particles even from originally homogeneous spatial distributions. In
the current work, we examine the effects of light sheet profile distortion and attenuation by tracer seeding particles, as
well as reflected light from local wall boundaries on the effective light sheet thickness. The effective thickness is critical
for concentration measurements, as it dictates the dispersed phase detection volume. A direct calibration method is demonstrated
to measure the effective light sheet thickness in a water/glass bead system, which shows that systematic bias errors on the
order of 30% can result if the reflective bed condition is not accounted for, and the errors can be as high as 50% or more
if a single-point measure of the sheet width is used. |
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