Abstract
An experimental and numerical analysis of the behavior of drops in a liquid matrix, in presence of temperature differences, is carried out in preparation for a MAXUS sounding rocket flight to study wetting and coalescence prevention induced by thermal Marangoni effect. On-ground experimentation has been carried out using micro zone apparatus. Different pairs of liquids (drop and matrix) have been analyzed; wetting prevention has been observed with drops of different diameter and critical temperature differences have been measured for each pair. To avoid buoyancy effects similar experiments have been carried out during the 30th ESA parabolic flight campaign. The main objective of the experiments is facility tests in a parabolic flight for the MAXUS flight. During the parabolic flight a hanging drop of Silicone oil 10 mm diameter has been injected in a matrix of Fluorinert and in air; wetting prevention has been observed in presence of a temperature difference between the drop and the lower surface. The theoretical-numerical study of the problem has been carried out with a thermofluidynamic model based on the assumption of the existence of a fluid film between the drop and the lower surface.
After the campaign, the video images of the experiment have been analyzed and velocity measurements have been obtained analyzing the motion of tracers. Measured and computed velocities are in sufficient agreement, in particular for the Silicone oil/Fluorinert configuration.
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Abbreviations
- ϕ:
-
disk diameter [m]
- Δ P:
-
pressure difference across the drop interface [N/m2]
- ρ:
-
density [Kg/m3]
- h:
-
cylinder length [m]
- ν:
-
kinematic viscosity [m2/s]
- n:
-
normal coordinate [m]
- P:
-
pressure [Pa]
- R:
-
drop radius [m]
- s:
-
tangential coordinate [m]
- T:
-
temperature [K]
- V:
-
velocity [m/s]
- Δ Tc :
-
critical temperature difference [K]
- Δ T:
-
temperature difference [K]
- Δ ρ:
-
density difference [Kg/m3]
- μ:
-
dynamic viscosity [Kg/m/s]
- σ:
-
interface tension [N/m]
- τ:
-
viscous shear stress [N/m2]
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Savino, R., Nota, F. & Fico, S. Wetting and coalescence prevention of drops in a liquid matrix. Ground and parabolic flight results. Microgravity Sci. Technol 14, 3–12 (2003). https://doi.org/10.1007/BF02870938
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DOI: https://doi.org/10.1007/BF02870938