MOLECULAR TAGGING FLUORESCENCE VELOCIMETRY (MTFV)
TO MEASURE MESO- TO MICRO-SCALE THERMAL FLOW FIELDS
2000 IMECE Conference Proceeding, November, 5-10, 2000, Orlando, Florida
J. S. Park, K. D. Kihm and D. M. Pratt
The development
of a molecular tagging fluorescence velocimetry (MTFV) system is
discussed and measurement results are presented for a meso-scale
flow field of thermally driven capillary pore of 5-mm inner diameter
that is tilted 5 degree from the horizon. The developed technique
uses caged Dextran conjugates of caged fluorescene dyes of less
than 10 nm in size for tracers. The frequency-tripled UV band (
= 355 nm) of a pulsed Nd:YAG laser uncages the molecules by
photo-cleaving that is decomposition of a caging chemical group
and a fluorescence chemical group. Then a CW blue Argon-ion laser
(
= 488 nm) pumps the fluorescence of only those uncaged molecules,
whose emmission band is centered at 
= 518 nm, and a sequential recording of the fluorescence images
are digitally recorded and analyzed for Lagrangian velocity field
mapping. The use of the technique allows detailed measurements of
the thermally driven three-dimensional flow inside a heated capillary
pore. The measurement shows that the meniscus surface flow is mainly
driven by the thermocapillary stress field, occurring due to the
surface temperature gradient, while the bulk flow inside the pore
is driven largely by the natural convection buoyancy. The
whole capillary flow is made by a combination of these two different
flow effects. As to the heater position, above or below the
interface, the three dimensional flow patterns are measured totally
in the opposite way.