Scientific and Technical Aerospace Reports Volume 39 April 6, 2001

20010024891 NASA, Washington, DC USA
Microgravity Sciences Program Overview
Trinh, E., NASA, USA; Proceedings of the Fifth Microgravity Fluid Physics and Transport Phenomena Conference; December
2000, pp. 4-17; In English; See also 20010024890; No Copyright; Avail: CASI; A03, Hardcopy; A10, Microfiche
This overview presents in viewgraph form, the NASA Program organization regarding fluid physics, physical sciences
research in space and the connection to biology, the dual thrust of the fluid physics program, and the immediate and future plans
of the physical science research division.
CASI
NASA Programs; Research Projects; Research Management
20010024892 Purdue Univ., West Lafayette, IN USA
Microgravity Research in Support of Technologies for the Human Exploration and Development of Space and Planetary
Bodies
Viskanta, R., Purdue Univ., USA; Proceedings of the Fifth Microgravity Fluid Physics and Transport Phenomena Conference;
December 2000, pp. 18-59; In English; See also 20010024890; No Copyright; Avail: CASI; A03, Hardcopy; A10, Microfiche
This document presents in viewgraph form, the history, purpose, scope, and technological challenges of the Committee on
Microgravity Research.
Author (revised)
Microgravity; Research Projects; Space Exploration; Research and Development
20010024893 Johns Hopkins Univ., Dept. of Mechanical Engineering, Baltimore, MD USA
Pressure-Radiation Forces on Vapor Bubbles
Prosperetti, A., Johns Hopkins Univ., USA; Hao, Y., Johns Hopkins Univ., USA; Oguz, H. N., Johns Hopkins Univ., USA; Proceedings
of the Fifth Microgravity Fluid Physics and Transport Phenomena Conference; December 2000, pp. 61-75; In English;
See also 20010024890; No Copyright; Avail: CASI; A03, Hardcopy; A10, Microfiche
At normal gravity, the effectiveness of boiling as a heat transfer mechanism relies in no small measure on the rapid removal
of vapor bubbles from the heated surface by buoyancy. This process has a two-fold benefit, as it both aids in removing latent heat
and in promoting microconvective motion near the surface. At low heat fluxes, in microgravity conditions complex bubble coalescence
phenomena help remove bubbles from the heated surface, but the effectiveness of this mechanism is limited and the critical
heat flux is reached at much lower wall superheats than on Earth. In order to increase the critical heat flux at low gravity it is therefore
desirable to remove bubbles from the heated surface providing a substitute for buoyancy. The objective of this work is to study
the suitability of acoustic pressure forces (also known as Bjerknes forces) as a means to achieve this end. This idea seems promising
because small bubbles (smaller than the resonant radius) tend to be attracted by sound pressure antinodes (such as those formed
near a solid heating surface), while larger bubbles are repelled by pressure antinodes. One can thus envisage a situation where,
as the vapor bubbles grow, they are eventually pushed away from the heated region. Furthermore there would be the additional
benefit of the local microconvection induced by the pulsating vapor bubbles. This argument ignores however the effect of the wall
on the pressure field produced by the pulsating bubble itself. This effect can be approximated by replacing the wall by an image
bubble, which would be pulsating in phase with the real bubble. It is known that such an image bubble exerts an attractive force
on the real bubble whatever its radius, and it is not obvious a priori which one of the two effects would prevail. Our calculations
show that, if the wavefronts are parallel to the solid surface, the attractive force of the image bubble prevails and the vapor bubble
is attracted by the wall. Obviously, it is impossible to achieve bubble removal with such an arrangement. However, if the wavefronts
are perpendicular to the wall, the bubble is pushed along the wall away from the pressure antinode once it grows past its
resonant radius and the objective of this investigation can be met. This work therefore suggests that acoustic forces can be used
to remove bubbles from the heated area provided conditions are such that the force is directed parallel to the rigid wall. The previous
results have been obtained with a pure vapor, spherical bubble model. In the continuation of this work deformation of the
spherical shape will be allowed and the simultaneous presence of an incondensable gas in the bubble will be considered.
Author (revised)
Bubbles; Sound Pressure; Boiling; Buoyancy; Gravitational Effects
20010024894 Johns Hopkins Univ., Dept. of Mechanical Engineering, Baltimore, MD USA
Experimental Investigation of Pool Boiling Heat Transfer Enhancement in Microgravity in the Presence of Electric Fields
Herman, C., Johns Hopkins Univ., USA; Proceedings of the Fifth Microgravity Fluid Physics and Transport Phenomena Conference;
December 2000, pp. 77-127; In English; See also 20010024890; No Copyright; Avail: CASI; A04, Hardcopy; A10, Microfiche
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