Are de-Orbiting Missions Possible using Electrodynamic Tethers? Review from the Space Debris Perspective
- Paper number
IAC-05-B6.3.01
- Author
Dr. Carmen Pardini, ISTI-CNR, Italy
- Coauthor
Prof. Toshiya Hanada, Kyushu University, Japan
- Coauthor
Dr. Luciano Anselmo, ISTI-CNR, Italy
- Coauthor
Dr. Hiroshi Hirayama, Kyushu University, Japan
- Year
2005
- Abstract
Vibrational convection provides a mechanism of heat and mass transfer due to the existence of mean flows. In weightlessness, it is an additional way of transporting heat and matter similar to thermo- and solutocapillary (Marangoni) convection. Mean flows show some similarity with gravity-induced convection and might serve as a way to control and operate fluids in space. The aim of this study is to analyze the physical mechanism by which vibrations affect the mixing characteristic of two miscible fluids which initially meet at a sharp horizontal interface. Here the results on numerical modeling of vibrational convection under reduced gravity are presented. The cubic cell of 10 mm length is filled with two miscible liquids: both liquids consist of the same components, water and isopropanol, in different proportions. The layer of heavier/denser liquid is at the bottom and lighter is on the top (gravitationally stable configuration). The system is kept at constant temperature. The vibrations are imposed along the interface. The density difference between liquids, i.e. ρ, is assumed to be small, i.e. Δρ/ρ(mean)<<1 and the Boussinesq approximation is valid. We consider high frequency vibrations, i.e. period of oscillations is smaller than viscous and diffusion times. Then all physical quantities, e.g. the concentration and velocity, may be presented as the superposition of a mean (slow) and pulsational (fast) parts. The calculations are performed in average approach. Therefore the viscosity and the diffusion coefficients are considered as function of concentration. The vibration excitation is characterized by the vibrational Rayleigh number, which is constant for given experimental conditions. We observed dynamics of different flow patterns as gravity level is varied. For zero gravity conditions the vibrations cause mean flow in such a way, that heavy/denser liquid moves up along the solid walls. The flow is similar to Kelvin-Helmholtz instability which is observed in free shear layers. Solid wall at the top impose constrain and these structures turn inside the cell, creating another flow organization, when the denser liquid is on top of the less dense. This scenario is similar to Rayleigh-Taylor instability in ground conditions (when heavy liquid is on the top). Thus, vibrations provide the conditions for reproducing some of the effects of gravity. Further the denser liquid starts to descend, being oscillatory. For this set of parameters the amplitudes of the velocity and of the concentration slowly decay with time.
- Abstract document
- Manuscript document
IAC-05-B6.3.01.pdf (🔒 authorized access only).
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