Capillary Flow Experiment-2 (CFE-2)
Research Area: Fluid Physics
Expedition(s): 25-ongoing
Principal Investigator(s): ● Mark Milton Weislogel, PhD, Portland State University,
Portland, Oregon
RESEARCH OBJECTIVES
Capillary Flow Experiments - 2 (CFE-2) is a suite of fluid physics experiments that investigates
how fluids move up surfaces in microgravity. The results aim to improve current computer
models that are used by designers of low-gravity fluid systems and may improve fluid transfer
systems for water on future spacecraft.
EARTH BENEFITS
Results of this study will improve the
understanding of fluid flow in
miniaturized biological devices used
for health screening and analysis; this
class of devices is often referred to as
lab-on-a-chip.
SPACE BENEFITS
Capillary resulting phenomena include
critical wetting in discontinuous
structures, and capillary flow in
complex containers. Specific
applications of these results center on
particular fluid challenges concerning
the storage, transport, and processing
of liquids in space. The knowledge
assists spacecraft fluid systems
designers in increasing system
reliability, decreasing system mass,
and reducing overall complexity.
RESULTS
The Vane Gap (VG) experiment identifies a fundamental wetting condition akin to the critical
corner wetting condition identified by Concus and Finn (1969), but for interior corners formed
by walls that possess a gap at the virtual axis of intersection of the two planar walls(i.e., vanes).
Such a "wall-vane gap" is common in spacecraft systems, but is treated as an ideal corner. The
Capillary Flow Experiment (CFE) involves many studies centered around a phenomenon called
wetting. Wetting describes the ability for a liquid to spread across a surface. The original CFE
tests were highly successful at uncovering the dynamics of wetting in microgravity. Capillary
Flow Experiments -2 (CFE-2) determines the critical wetting conditions for screens and
perforated plates for perfectly wetting fluids. The impact of such porous substrateshas
The primary science goal for the Vane Gap experiments is to
find the critical wetting angles at which fluid wicks up the edges
of a perforated vane. An unexpected phenomenon (seen left)
occurs when the perforations are filled prior to the running of the
experiment. A bulk shift of the fluid is easily identified when the
perforations are filled, and stands out distinctly when compared
to the relative symmetry of a test run with un-filled perforations.
Mark Weislogel image.