並列タイトル等円筒橋中の高プラントル数流体の熱毛細管対流についての実験的及び数値的研究
タイトル(掲載誌)宇宙開発事業団技術報告: Marangoni Convection Modeling Research: Annual Report April 1, 2001-March 31, 2002 = NASDA Technical Memorandum: Marangoni Convection Modeling Research: Annual Report April 1, 2001-March 31, 2002
一般注記An experimental study has been conducted to clarify characteristics of oscillatory Marangoni convection in a liquid bridge suspended between two coaxial disks heated differentially. The disk diameter is 5 mm and the working fluid is 5cSt silicone oil. The aspect ratios and volume ratios examined are (Ar, V/V(sub 0)) = (0.5, 0.62), (0.5, 1.00), (0.33, 1.00). Simultaneous visualization of flow field and surface temperature is performed to understand their relationship during oscillation. It is shown that a pulsating mode of oscillation first appears and then the mode undergoes a transition to a rotating mode at a slightly higher temperature difference, Delta-T. The azimuthal mode number is m = 1/Ar for both pulsating and rotating modes. It is found that the pulsating and rotating modes can exist simultaneously for (Ar, V/V(sub 0)) = (0.5, 1.00), leading to a beat signal in surface temperature oscillation. A numerical calculation is done to clarify the heat-transfer characteristics of the Marangoni (or thermocapillary) convection in a liquid bridge suspended between differentially heated disks (i.e., a half-floating-zone model). Flow and temperature fields both in the liquid bridge and in the surrounding air are calculated simultaneously to evaluate the rate of heat transfer at the liquid-air interface. A commercially available CFD code is used to solve the governing equations coupled with the thermocapillary boundary condition that is incorporated into the code as a body-force term. Five different conditions giving a range of Marangoni number of 13,300-32,800 are considered. The computed velocity field in the air has revealed the presence of a recirculating zone near the liquid surface. It is generated by the two competing forces, i.e., the vertically downward shear stress due to the surface flow and the vertically upward force due to the buoyancy. The computed velocity field compares favorably with the experimental one measured by using particle image velocimetry. The temperature field computed is analyzed to evaluate the rate of heat flow from the liquid to the air. Under the present conditions, the rate of heat transfer is 0.022-0.039 W and increases monotonously with the temperature difference between the disks. The contribution of thermal radiation is estimated to be 30-40 percent. The Biot number corresponding to the convective part of the heat flow is 0.18-0.21 or 0.21-0.23, depending on the choice of temperature difference for the definition of heat-transfer coefficient. The rate of heat loss evaluated numerically is compared with the experimental data reported previously.
資料番号: AA0045403002
レポート番号: NASDA-TMR-020026E
一次資料へのリンクURLhttps://jaxa.repo.nii.ac.jp/?action=repository_action_common_download&item_id=42848&item_no=1&attribute_id=31&file_no=1
連携機関・データベース国立情報学研究所 : 学術機関リポジトリデータベース(IRDB)(機関リポジトリ)
提供元機関・データベース宇宙航空研究開発機構 : 宇宙航空研究開発機構リポジトリ