Scientific and Technical Aerospace Reports Volume 39 April 6, 2001

moons when disturbed by low velocity impacts and perturbations. These include naturally occurring impacts as well as disturbances
to the surface from human and spacecraft activity. The velocity distribution of the ejecta determines the amount of material
launched to various altitudes above the surface and escaping the parent body. This information is important for spacecraft instruments
landing on airless bodies with low surface gravity and powdery regoliths.
Author (revised)
Collisions; Dust; Gravitational Effects; Low Speed; Microgravity; Impact; Energy Dissipation
20010024975 Colorado Univ., Dept. of Chemical Engineering, Boulder, CO USA
Surface Collisions Involving Particles and Moisture (SCIPM)
Davis, R., Colorado Univ., USA; Wilson, H., Colorado Univ., USA; Rager, D., Colorado Univ., USA; Zhao, Y., Colorado Univ.,
USA; Proceedings of the Fifth Microgravity Fluid Physics and Transport Phenomena Conference; December 2000, pp.
1347-1348; In English; See also 20010024890; No Copyright; Abstract Only; Available from CASI only as part of the entire parent
document
Collisions of particles with wet surfaces are important in many industrial and natural applications, including filtration,
agglomeration, wet granular flow, and pollen capture. A fundamental study of such collisions is underway in our laboratory. Current
experimental work involves dropping small plastic and metal balls onto a surface which is overlaid with a thin layer of a viscous
fluid and tilted at an angle to the gravity vector. Critical conditions at which the spheres bounce instead of sticking to the
surface are determined with the aid of high-frequency strobotic photography. When bouncing does occur, the rebound velocity,
angle, and rotation are determined from image analysis of the photographs. Preliminary results show that bouncing increases with
increasing ball size and impact speed, and with decreasing viscosity and thickness of the fluid layer. The results are interpreted
using elastohydrodynamic theory, accounting for lubrication pressure in the thin viscous layer and Hertzian deformation of the
solid ball and opposing surface. The laboratory experiments are restrict to high impact velocities (approximately 1 m/s, or higher),
as otherwise gravitational acceleration obscures the rebound. As a result, relatively thick and viscous fluids layers on the surface
are required to observe the transition between bouncing and sticking. Future experiments with lower impact speeds (approximately
0.1 m/s, or lower) and surfaces wetted with water are planned for a low-gravity environment.
Author (revised)
Collisions; Elastohydrodynamics; Viscous Fluids; Impact Velocity
20010024976 NASA Glenn Research Center, Cleveland, OH USA
Stereo Imaging Velocimetry of Mixing Driven by Buoyancy Induced Flow Fields
Duval, W. M. B., NASA Glenn Research Center, USA; Jacqmin, D., NASA Glenn Research Center, USA; Bomani, B. M., NASA
Glenn Research Center, USA; Alexander, I. J., NASA Glenn Research Center, USA; Kassemi, M., NASA Glenn Research Center,
USA; Batur, C., NASA Glenn Research Center, USA; Tryggvason, B. V., NASA Glenn Research Center, USA; Lyubimov, D.
V., NASA Glenn Research Center, USA; Lyubimova, T. P., NASA Glenn Research Center, USA; Proceedings of the Fifth Microgravity
Fluid Physics and Transport Phenomena Conference; December 2000, pp. 1349-1351; In English; See also 20010024890;
No Copyright; Abstract Only; Available from CASI only as part of the entire parent document
Mixing of two fluids generated by steady and particularly g-jitter acceleration is fundamental towards the understanding of
transport phenomena in a microgravity environment. We propose to carry out flight and ground-based experiments to quantify
flow fields due to g-jitter type of accelerations using Stereo Imaging Velocimetry (SIV), and measure the concentration field using
laser fluorescence. The understanding of the effects of g-jitter on transport phenomena is of great practical interest to the microgravity
community and impacts the design of experiments for the Space Shuttle as well as the International Space Station. The
aim of our proposed research is to provide quantitative data to the community on the effects of g-jitter on flow fields due to mixing
induced by buoyancy forces. The fundamental phenomenon of mixing occurs in a broad range of materials processing encompassing
the growth of opto-electronic materials and semiconductors, (by directional freezing and physical vapor transport), to solution
and protein crystal growth. In materials processing of these systems, crystal homogeneity, which is affected by the solutal
field distribution, is one of the major issues. The understanding of fluid mixing driven by buoyancy forces, besides its importance
as a topic in fundamental science, can contribute towards the understanding of how solutal fields behave under various body
forces. The body forces of interest are steady acceleration and g-jitter acceleration as in a Space Shuttle environment or the International
Space Station. Since control of the body force is important, the flight experiment will be carried out on a tunable microgravity
vibration isolation mount, which will permit us to precisely input the desired forcing function to simulate a range of body forces.
to that end, we propose to design a flight experiment that can only be carried out under microgravity conditions to fully exploit
the effects of various body forces on fluid mixing. Recent flight experiments, by the P.I. through collaboration with the Canadian
Space Agency (STS-85, August 1997), aimed at determining the stability of the interface between two miscible liquids inside an
enclosure show that a long liquid column (5 cm) under microgravity isolation conditions can be stable, i.e. the interface remains
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