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Associate
Professor; Associate Director, Center for Advanced Polymer and Composite
Engineering
(614) 292-2256; koelling.1@osu.edu
Education
B.S., University of Missouri-Rolla,
1988
Ph.D., Princeton University, 1992
Honors
NSF/Lucent Technologies
Industrial Ecology Faculty Fellow, 1997
NSF Career Award,
1996
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 My
current research interests are in the rheology and processing of complex
fluids, including polymer melts and solutions. One of the most difficult
challenges in rheometry is the measurement of extensional viscosities.
This material property is of fundamental importance in many polymer processing
operations, including fiber spinning, blow molding,
and injection molding,
and in a variety of phenomena including turbulent drag reduction, jet stability,
and anti-misting. Four extensional rheometers based on techniques of fiber
spinning, stagnation point flow, contraction flow, and filament stretching
have been developed in our lab to measure the extensional viscosities of
complex fluids. Using these rheometers we are addressing the following
important questions. Are extensional flow properties the additional information
needed to characterize the
behavior of viscoelastic fluids? Can existing
constitutive equations properly describe both shear and extensional material
functions of viscoelastic fluids?
My
research group is also studying the dynamics of gas bubble penetration
through viscous and viscoelastic fluids. This problem has practical applications
in gas
-assisted injection molding, enhanced oil recovery, thermoset composite
processing, and a variety of coating processes. Gas-assisted injection
molding is a novel process which involves the partial injection of polymer
melt into a mold cavity, followed by injection of high-pressure gas. The
gas penetrates through the viscous polymer melt and hollows out the interior
of the mold cavity.
 This
process is capable of producing light-weight, rigid plastic parts with
improved surface quality. The effects of processing conditions and polymer
rheology on gas penetration through the molded part are being investigated.
Fundamental free surface flow studies are also being conducted to determine
how bubble dynamics are influenced by viscoelasticity and non-isothermal
flow behavior. Computational fluid dynamics are being u
sed in conjunction
with experimental studies to determine the important physics required to
determine bubble shape and hydrodynamic coating thickness.
Other
areas under investigation include transport problems involving void formation
and removal in thermoset composite processing, thin-wall injection molding,
mi
crocellular foam processing, microfluidic devices, and development of
biocompatible polymers. |
