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Influence of Variable Viscosity on the Onset of Hydrothermal Waves in Thermocapillary Liquid Bridges
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1999
Year
Variable ViscosityEngineeringFluid MechanicsMechanical EngineeringThreshold ShiftConvective Heat TransferMixed ConvectionNumerical SimulationFloat-zone Crystal-growth ProcessRheologyTransport PhenomenaThermocapillary Liquid BridgesThermophysicsThermodynamicsNatural ConvectionHydrothermal FluidHydrodynamic StabilityPhysicsHeat TransferMultiphase FlowHalf-zone ModelCivil EngineeringApplied PhysicsHydrothermal WavesThermal Engineering
The float-zone crystal-growth process is investigated in the framework of the half-zone model. The influence of a temperature-dependent viscosity on the axisymmetric steady thermocapillary flow and its stability with respect to nonaxisymmetric perturbations is examined by means of a linear-stability analysis. The onset of oscillatory convection is studied numerically by a mixed Chebyshev-collocation finite-difference method. Detailed calculations have been carried out for PR = 4 and unit aspect ratio. It is found that the temperature-dependent viscosity decreases the critical Reynolds number for the onset of three-dimensional flow. Since the threshold shift is a function of the azimuthal wavenumber of the neutral mode, the critical mode may depend on the magnitude of the viscosity variation.