Experimental and numerical analysis of three-dimensional surface tension and buoyancy-driven flows in cavities

R. Savino, M. Lappa, D. Paterna

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Abstract

Surface tension and buoyancy-driven convection in a fluid cell filled with 10 cs silicone oil is studied experimentally and numerically. The experiments are carried out with a facility equipped with two "surface heaters" and two "bulk heaters" controlled independently by circulating water from four independent thermostats. The diagnostic system consist of a thermographic visualisation system based on an infrared thermocamera (a thermocamera with wavelengths 8-12 mm has been employed that does not make the silicone oil transparent allowing thus a direct investigation of the surface behaviour of the temperature field) and of a videocamera that captures images of different vertical planes, illuminated with a 1mm thick light sheet. A PIV (particle image velocimetry technique) is used to obtain the velocity field. The complex three-dimensional flow structure, due to the combined effect of buoyancy and Marangoni flow is, investigated by three-dimensional, time-dependent numerical solutions of the model equations and by on ground experimentation. The field equations are numerically solved with three-dimensional control volume methods in a staggered uniform grid. The numerical results, in agreement with the experimental ones, show that the flow field structure may be very complex depending on the presence and relative orientation (parallel or antiparallel) of the surface and bulk temperature gradients. In the case of concurrent buoyancy and Marangoni effects a complex three-dimensional flow and temperature pattern arises, showing the existence on the free surface of “temperature fingers” protruding from the hot side toward the cold side of the interface. The numerical and experimental analyses show that the number of spots is related to the value of the applied temperature gradients.
Original languageEnglish
Pages (from-to)12-24
Number of pages13
JournalMicrogravity & Space Station Utilization (MSSU)
Volume2
Issue number1
Publication statusPublished - 2001

Keywords

  • buoyancy-driven convection
  • surface tension
  • fluid filled cell
  • numerical analyses
  • thermographic visualisation system
  • particle image velocimetry technique
  • Marangoni flow

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