With
the help of an award-winning paper by co-investigators Carlos Coimbra
and
Roger Rangel, scientists
will someday be able to use the
three-dimensional
light patterns of holography to see how bubbles and
particles
interact in microgravity conditions. The paper, which received the
American
Institute of Aeronautics and Astronautics' Best Paper in
Microgravity
Science Award for 1999, forms the theoretical foundation for
SHIVA, or
Spaceflight Holography Investigation in a Virtual Apparatus.
Principal
Investigator James Trolinger, of MetroLaser Inc., in Irvine,
California;
Rangel, of the University of California, Irvine, Coimbra, of the
University
of Hawaii, and other members of the SHIVA team at Marshall Space
Flight
Center, will collect data using a unique holography-based diagnostics
tool.
They'll use the instrument to understand the intricate, transient
interaction
between a single bubble or particle and its surrounding viscous
fluid
as well as bubble or particle interactions among themselves and the
fluid.
Findings from the experiment, which will be conducted on a space
shuttle
flight or on the International Space Station, will help scientists better
understand
the physics of most diffusion processes. For example, the
bubbles
in a glass of ginger ale on Earth travel quickly toward the top of the
liquid
because of buoyancy forces. In a microgravity environment, buoyancy
forces are greatly reduced, so they have
little influence on the motion of the
bubbles.
Recording the behavior of bubbles in this environment will allow
SHIVA
researchers to study in detail the motion and velocity history of the
bubbles.
What the researchers learn can be applied to manufacturing
processes
on Earth, where bubbles can cause defects if they remain in a
molten
material as it hardens.
The
experiment will allow results obtained for particles 1-2 millimeters in
size
moving at fairly low frequencies (around 100 hertz) to be scaled down
and
applied to microparticles and nanoparticles in Brownian motion, the
apparently
erratic zigzag motion of microscopic particles that becomes
more
evident at raised temperatures, in less viscous fluid, or with a smaller
particle
size. The paths that the particles take become increasingly
complicated
as they enter the viscoelastic regime, which means that the
path
and velocity of a particle at any given moment depends on its entire
path
and all its previous velocities leading up to that moment. Scientists can
determine
where a particle will go and at what speed based on that
information.
Coimbra
and Rangel presented their paper, "Spherical Particle Motion in
Unsteady
Viscous Flows," at the 37th Aerospace Science Meeting in
January
2000.