Scientific and Technical Aerospace Reports Volume 39 April 6, 2001

2.2-second drop tower at NASA Glenn Research Center. Analysis indicates that 2.2 seconds is sufficient to observe the characteristics
of the instability. The rig that will be constructed is envisioned to be roughly 0.9 m long, 0.4 m wide, and 0.8 m high, to fit
in the frame used in the drop-tower experiments. The rig will house the experimental set up and the data-acquisition and photography
systems. The experimental set up will be identical to that used in the ground-based experiments. The gas and liquid coflow
will be injected vertically upward; the injected gas will collect at the top and will be vented out. Photographs of the gas jet will
be obtained using a high-speed motion picture camera. The images will be analyzed to measure the disturbance growth rates and
velocities. The electrical system will be designed to enable remote operation of the experiment. Theoretical work to be undertaken
includes analysis to demarcate the mode of instability: absolute or convective for general three-dimensional disturbances over
the range of operating parameters. Also, a non-linear stability analysis will be used to study the growth of large-amplitude disturbances,
with and without buoyancy effects.
Author (revised)
Bubbles; Gas Injection; Gas Jets; Gas-Liquid Interactions; Stability
20010024960 NASA Marshall Space Flight Center, Huntsville, AL USA
Fluid Physics and Macromolecular Crystal Growth in Microgravity
Pusey, M., NASA Marshall Space Flight Center, USA; Snell, E., NASA Marshall Space Flight Center, USA; Judge, R., NASA
Marshall Space Flight Center, USA; Chayen, N., Imperial Coll. of Science, Technology and Medicine, UK; Boggon, T., Manchester
Univ., UK; Proceedings of the Fifth Microgravity Fluid Physics and Transport Phenomena Conference; December 2000, pp.
1260-1262; In English; See also 20010024890; No Copyright; Abstract Only; Available from CASI only as part of the entire parent
document
The molecular structure of biological macromolecules is important in understanding how these molecules work and has direct
application to rational drug design for new medicines and for the improvement and development of industrial enzymes. In order
to obtain the molecular structure, large, well formed, single macromolecule crystals are required. The growth of macromolecule
crystals is a difficult task and is often hampered on the ground by fluid flows that result from the interaction of gravity with the
crystal growth process. One such effect is the bulk movement of the crystal through the fluid due to sedimentation. A second is
buoyancy driven convection close to the crystal surface. On the ground the crystallization process itself induces both of these
flows. Buoyancy driven convection results from density differences between the bulk solution and fluid close to the crystal surface
which has been depleted of macromolecules due to crystal growth. Schlieren photograph of a growing lysozyme crystal illustrating
a ’growth plume’ resulting from buoyancy driven convection. Both sedimentation and buoyancy driven convection have a
negative effect on crystal growth and microgravity is seen as a way to both greatly reduce sedimentation and provide greater stability
for ’depletion zones’ around growing crystals. Some current crystal growth hardware however such as those based on a vapor
diffusion techniques, may also be introducing unwanted Marangoni convection which becomes more pronounced in microgravity.
Negative effects of g-jitter on crystal growth have also been observed. to study the magnitude of fluid flows around growing crystals
we have attached a number of different fluorescent probes to lysozyme molecules. At low concentrations, less than 40% of
the total protein, the probes do not appear to effect the crystal growth process. by using these probes we expect to determine not
only the effect of induced flows due to crystal growth hardware design but also hope to optimize crystallization hardware so that
destructive flows are minimized both on the ground and in microgravity.
Author (revised)
Marangoni Convection; Crystal Growth; Crystal Surfaces; Crystallization; Depletion; Fluid Dynamics; Macromolecules
20010024961 Princeton Univ., Dept. of Chemical Engineering, NJ USA
Electrohydrodynamic Flows in Electrochemical Systems
Saville, D. A., Princeton Univ., USA; Proceedings of the Fifth Microgravity Fluid Physics and Transport Phenomena Conference;
December 2000, pp. 1263-1274; In English; See also 20010024890; No Copyright; Avail: CASI; A03, Hardcopy; A10, Microfiche
Recent studies disclose that electrohydrodynamic flow is often present in electrochemical systems. Nevertheless, our understanding
of electrohydrodynamics (EHD) is largely confined to situations involving fluid interfaces with apolar liquids or electrokinetics
in aqueous systems. Neither addresses events involving electrodes. This work centers on this new class of flows -
electrohydrodynamic motion in systems with electrochemical reactions Experiments on well-characterized systems are proposed
along with theoretical work on the relevant model equations. In addition to their scientific value, the results will have technological
applications since they provide insight into ways of controlling small-scale fluid motion - EHD pumping or patterning, for example.
A two-part program is envisioned. In the experimental part, flows in the region between two electrodes will be studied with
homogeneous and patterned electrodes. With homogeneous electrodes, motions arising from electrohydrodynamic instabilities
will be investigated. With patterned electrodes, flow is engendered by lateral current inhomogenities on an electrode. Because
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