Kazuyuki Higashino

Direct numerical simulation of oscillatory Marangoni convection in cylindrical liquid bridges

A three-dimensional oscillatory Marangoni (thermocapillary) convection with Prandtl number Pr=16.0849 and Marangoni number Ma=3.30508×104 in a large aspect ratio (As=H/R) range, As=0.2–4, in a silicone oil liquid bridge with a non-deformable cylindrical surface is investigated by the finite volume method. The azimuthal wave numbers 1, 2, 3, 4, 5, 6, 10 and 16 are obtained for different aspect ratios, As. The dimensionless main frequency of periodic or quasi-periodic temperature oscillations strongly depends on aspect ratio, As. increases with the increment of As with approximately a bi-linear relation, and its gradient for As=0.2–1 is less than that for As>1. The periodic and quasi-periodic oscillations are found to depend on aspect ratio, As, for fixed Pr and Ma.

Three-dimensional oscillatory thermocapillary convection in liquid bridge under microgravity

Abstract Three-dimensional oscillatory thermocapillary convection in silicone oil liquid bridge is studied numerically by means of finite volume method (FVM). The results reveal the existence of two different oscillatory modes: pulsating and rotating oscillations. Close to the onset of oscillation, the pulsating oscillatory convection is observed. With the increment of Marangoni number Ma, the pulsating oscillatory convection is replaced by rotating oscillatory convection, where the temperature and velocity fields demonstrate the characteristics of rotation. An approximately linear relationship between Ma and dimensionless main frequency f*=fH2ϰ−1 is found for As=4.0 in periodic oscillatory regime. This relationship becomes a little more complex for As=1.0.

Usefulness of experiments with model fluid for thermocapillary convection—effect of Prandtl number on two-dimensional thermocapillary convection

The floating zone technique is promising to realize large, high-quality crystals under microgravity. Thermocapillary flow, which is the dominant convection in a floating zone under microgravity, has been widely reported in the literature to be extremely sensitive to the Prandtl number Pr. In the present study, the effect of Pr on steady thermocapillary convection is re-evaluated based on both analytical and numerical solutions. The results indicate that an approximate similarity of temperature and velocity structures in a large Pr range is realized under suitable conditions, fixing the Marangoni number Ma, in steady two-dimensional regime.

Marangoni convection in model of floating zone under microgravity

Marangoni convection in a half-zone model, a simplification of the floating zone model, is steady and axisymmetric for Marangoni number Ma5Mac, but the azimuthal flow after instability (Ma>Mac) breaks the axial-symmetry, and m-foldsymmetry of the flow pattern is observed. The symmetry number m (azimuthal wave number) depends strongly on the aspect ratio, As (As=height/radius), of the half-zone. Based on the results of numerical simulation, the nature of the correlation between m andAs is investigated # 2001 Elsevier Science B.V. All rights reserved.

Numerical simulation of convection depth in shear cell under microgravity

Abstract By applying the idea of an isotope trace experiment, the concept of isotope trace in hydrodynamics simulation is proposed. The isotope concentration is conceived as a numerical marker to trace the convection and estimate numerically the convection depth due to shearing in shear cell under microgravity. Two different shearing rates, 2mm/s and 20mm/s, are investigated, and results demonstrate that the isotope depths are same for both cases at the termination of shearing, but the effect of residual flow field after shearing is different.

Numerical simulation of oscillatory thermocapillary convection in liquid bridges

The floating zone technique is a promising containerless method to realize larger and high-quality crystals of semiconductors under microgravity. Thermocapillary convection, which is caused by the presence of unbalanced surface tension in floating zone, is important for mass and heat transport in crystal growth and is studied with half- zone liquid bridge model in present paper. The free surface of liquid bridge is idealized as non-deformable and adiabatic from the environmental gas. the 3D oscillatory thermocapillary flow is investigated numerically by directly solving incompressible Navier-Stokes, energy and continuity equations with finite volume method. The surface tension is added directly in Navier-Stokes equations. the relationship between Marangoni number Ma and dimensionless frequency f* equals fH2κ-1 and also flow structures are studied.