Vapor-Gas Bubble Evolution and Growth in Extremely Viscous Fluids Under VacuumFormation of vapor and gas bubbles and voids is normal and expected in flow processes involving extremely viscous fluids in normal gravity. Practical examples of extremely viscous fluids are epoxy-like filler materials before the epoxy fluids cure to their permanent form to create a mechanical bond between two substrates. When these fluids flow with a free liquid interface exposed to vacuum, rapid bubble expansion process may ensue. Bubble expansion might compromise the mechanical bond strength. The potential sources for the origin of the gases might be incomplete out-gassing process prior to filler application; regasification due to seal leakage in the filler applicator; and/or volatiles evolved from cure reaction products formed in the hardening process. We embarked on a study that involved conducting laboratory experiments with imaging diagnostics in order to deduce the seriousness of bubbling caused by entrained air and volatile fluids under space vacuum and low gravity environment. We used clear fluids with the similar physical properties as the epoxy-like filler material to mimic the dynamics of bubbles. Another aspect of the present study was to determine the likelihood of bubbling resulting from dissolved gases nucleating from solution. These experimental studies of the bubble expansion are compared with predictions using a modified Rayleigh- Plesset equation, which models the bubble expansion.
Document ID
20090019007
Acquisition Source
Glenn Research Center
Document Type
Conference Paper
Authors
Kizito, John (North Carolina Agricultural and Technical State Univ. Greensboro, NC, United States)
Balasubramaniam, R. (National Center for Space Exploration Research on Fluids and Combustion Cleveland, OH, United States)
Nahra, Henry (NASA Glenn Research Center Cleveland, OH, United States)
Agui, Juan (NASA Glenn Research Center Cleveland, OH, United States)
Truong, Duc (NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
August 24, 2013
Publication Date
March 1, 2008
Subject Category
Fluid Mechanics And Thermodynamics
Report/Patent Number
NASA/TM-2009-215606E-16896AIAA-2009-1147
Meeting Information
Meeting: 47th Aerospace Sciences Meeting and Exhibit
Location: Orlando, FL
Country: United States
Start Date: January 5, 2009
End Date: January 8, 2009
Sponsors: American Inst. of Aeronautics and Astronautics