Virtual Bubbles Featured in AIAA Best Paper


Posted April 18, 2000


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



Coimbra and Rangel presented their paper, "Spherical Particle Motion in

Unsteady Viscous Flows," at the 37th Aerospace Science Meeting in

January 2000.


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