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形態: カラー図版あり, Physical characteristics: Original contains color illustrations, 資料番号: DS1440106000

This paper reports the overview of Dynamic Surf project conducted in the Japanese Experiment Module Kibo on board the International Space Station (ISS), especially focusing on the experimental conditions, the measurement systems, and the g-jitter effects. Oscillatory Marangoni convection in the liquid bridge is associated with oscillatory motion of the liquid-gas interface due to velocity oscillation inside the liquid bridge, where such a motion is called dynamic surface deformation (DSD). The present project aims at understanding the DSD effect in the transition mechanisms of temperature gradient-driven Marangoni convection in large-scale liquid bridges of high-Prandtl-number fluids through the longterm microgravity experiments on board the ISS. A series of microgravity experiments have been conducted in the period from September 2013 to November 2016 to understand the instability mechanisms and the role of DSD in Marangoni convection., 形態: カラー図版あり, Accepted: 2018-01-09, Physical characteristics: Original contains color illustrations, 資料番号: DS1740406000

Thermocapillary flow in a shallow annular pool (Ri=20 mm, Ro=40 mm and depth d=1.0 mm) of silicone oil (0.65 cSt, Pr=6.7), heated from the outer wall and cooled at the inner wall, is investigated by numerical simulation. Numerical results clarified details of pattern formation and oscillatory behavior of hydrothermal waves (HTW) as well as the critical conditions for their incipience. In non-rotating pool, the critical Marangoni number Mac for the incipience of the HTW is 8.396×10^3(ΔTc=5.03K). The critical azimuthal wave number mc is 27. At slightly super critical conditions, a single group of HTW propagating in the azimuthal direction is dominant after a long calculation time. Further increase in Ma causes coexistence of several groups of HTW with different wave numbers and propagation directions. Effect of a slow rotation of the pool around its central axis destabilizes the basic steady axisymmetric flow against HTW. At Ta=0.322 (corresponding to a rotation rate of 2 r.p.m.), the Mac was determined as 8.096×10^3(ΔTc=4.85K) with mc=30. Over a range of Ma from 8.76×10^3 to 2.0×10^4, numerical simulations indicate that the HTW propagates azimuthally opposite to the direction of the pool rotation in a rotating coordinate. This phenomenon, i.e. a selection of propagation direction, is caused by the azimuthal velocity component in the basic flow field induced by the Coriolis force. At Ma=1.34×10^4, the azimuthal wave number m increases up to 54 accompanied by an appearance of finger-shaped patterns. At Ma=2.0×10^4, two groups of HTW with greatly different wave numbers (m=48 and m=5) coexist and propagate in the opposite azimuthal directions.

Transition mechanism to oscillatory thermocapillary flow of high Prandtl number fluid, which still remains open, has been studied in a liquid bridge configuration. In this proposal, dynamic surface deformation (DSD) effects in the transition are focused on and some experiments are conducted using large liquid bridges in which a long duration microgravity environment is indispensable for doing them. Amplitude of DSD, critical temperature difference, surface temperature field, and flow field will be precisely measured near the onset point. The obtained data will be compared with prediction by a physical model of the oscillation mechanism including DSD and validity of the model will be clearly shown., 資料番号: AA0046917052

Silicon dioxide (SiO2) films were deposited by afterglow-plasma-enhanced CVD using triethoxysilane (TRIES) and tetraethoxysilane (TEOS) as source materials. TRIES has approximately four times higher vapor pressure than TEOS. The growth rate using TRIES was approximately twice as high as that using TEOS under the same operating conditions. The step coverage of film grown by TRIES was better than that by TEOS under a wide range of operating conditions. These results suggest that TRIES is a good candidate for SiO2 films.

Several sets of numerical simulations were conducted to give realistic understandings of oscillatory Marangoni convection in half-zone liquid bridges of low Prandtl number fluid with various aspect ratios (from 0.6 to 2.2). Special emphasis was placed on the effects of the less-conductive supporting rods on the transition from axisymmetric steady flow to three dimensional steady and also to oscillatory three dimensional flow. The new simulation results revealed that the conductive heat transfer through the small gaps (1 mm in total) between the melt/rod interface and the temperature measuring points causes significant temperature drop which provide with serious error in estimating Marangoni numbers. This conductive temperature drop is the major reason of the discrepancy between the numerical results in preceding years and the experimental results obtained in NASDA. The effect of the finite conductivity of the rods causes additional effect through the non-uniform temperature distributions on the melt/rod interface. This effect is not negligible but yet minor., 資料番号: AA0045403005, レポート番号: NASDA-TMR-020026E

A set of numerical simulations was conducted to understand characteristics of oscillatory Marangoni convection in half-zone liquid bridges with various aspect ratios (from 0.6 to 2.2) and Prandtl numbers (from 0 to 0.02) by a finite difference method. The simulation results indicated that under smaller temperature differences the flow in the liquid bridge is axisymmetric but it becomes unstable against a three dimensional disturbances beyond a certain threshold value of temperature difference. The flow becomes steady three dimensional. This steady flow becomes unstable against time dependent three dimensional disturbance beyond a second critical condition. The numerical simulations revealed the critical conditions, 3 D structure of disturbances and oscillation modes. The first critical conditions showed good agreements with those of linear stability analyses. The second critical conditions also agreed with previous values and gave new critical values for wide range of aspect ratio. Based on these simulations, a flow map was proposed for Pr = 0 fluid. Critical Reynolds numbers, flow mode and types of oscillations were also determined for Pr = 0.01 and 0.02 fluids., 資料番号: AA0032601005, レポート番号: NASDA-TMR-010015E

Three-dimensional (3-D) numerical simulations of oscillatory Marangoni flow were conducted for half-zone liquid bridges of Pr=1 fluid with different aspect ratios (0.75-1.60) and over a wide range of Marangoni number. Growth rate constants β of 3-D disturbances were determined as functions of the Marangoni number. The critical Marangoni number Ma_c, i.e, the stability limit of the axisymmetric steady flow, was determined by extrapolating β to zero. Thus determined critical Marangoni numbers show good agreement with those of linear stability analyses. A rough estimation predicts a correlation Ma_a/Ma_c ∝ a2 for large liquid bridges, where a is the liquid bridge radius and Ma_a is some `apparent critical Marangoni number' at which the 3-D oscillatory flow can be detected experimentally within a constant observation time to. Present result predicts an extremely long observation time for experimental determination of the true critical Marangoni number.

非定常3次元数値解析を、差分法を用いて、非変形円柱表面を有する半領域液橋(半径aおよび長さL)における振動マランゴニ対流に対して行った。4つの異なるアスペクト比、As(=L/a)=0.75、1.0、1.33および1.60を持つPr(プラントル数)=1の断熱液橋と、As=1.8を持つPr=0.02の液橋における温度場および速度場を、種々のマランゴニ数(Ma)のもとで計算した。Pr=1.0の流体に対する結果は、軸対称から3-D(3次元)流動への遷移が、マランゴニ数と先に経験した流動構造に依存して、異なる方位波数(m=1,2,3および4)と2種類の振動、即ち脈振動および回転振動を持つ高プラントル数流体にある進行熱水波を伴うことを示した。しかしながら、低プラントル数流体の液橋においては、線形安定性解析による予測と同様に、初期の不安定性が安定な3-D流動をもたらした。大きなマランゴニ数においては、明瞭な回転運動を示さない3次元振動流動を引き起こす第2の不安定性が発生した。本シミュレーションは、また、3-D外乱が時間と共に指数関数的に増大することを示した。この増大速度定数は、マランゴニ数の関数として求められた。結果として得られた限界マランゴニ数値は、線形安定性解析および数値シミュレーションにより推定した値と良い一致を示した。, Unsteady three dimensional numerical simulations were conducted for oscillatory Marangoni convection in half zone liquid bridges (radius a and length L) with non-deformable cylindrical surface by means of a finite difference scheme. Temperature and velocity fields were calculated in an adiabatic liquid bridge of Pr (Prandtl number) = 1 fluid with four different aspect ratios, As (= L/a) = 0.75, 1.0, 1.33 and 1.60, and also in liquid bridge of Pr = 0.02 with As = 1.8, under various Marangoni numbers (Ma). The results for a liquid of Pr = 1.0 indicated the transition from an axisymmetric to three dimensional flow is accompanied by traveling hydrothermal waves in high Prandtl number fluid with different azimuthal wave numbers (m = 1, 2, 3 and 4) and two types of oscillation, i.e., pulsating and rotating oscillations, depending on the Marangoni number and the flow structure previously experienced. In low Prandtl number fluid liquid bridges, however, the first instability brings out a steady three dimensional flow, as linear stability analyses predicted. At larger Marangoni numbers, there occurs a second instability to initiate a three dimensional oscillatory flow which does not indicate distinguishable rotating motion. The present simulations also revealed that the three dimensional disturbance grow exponentially with time. The growth rate constants were determined as a function of the Marangoni number. The resultant critical Marangoni number values show good agreements with those predicted by linear stability analysis and previous numerical simulations., 資料番号: AA0002209005, レポート番号: NASDA-TMR-990007E

This report was described the activity of a research working group on Interfacial Phenomena and fluid instability. Primary three themes which would promise to utilize the microgravity condition were discussed. The research plan and organization concerning these themes were established. We start the preparatory study to accomplish each objective., 資料番号: AA0063349026

第2回探査ロケット実験TR-1A(宇宙実験用小型ロケット)(1992)では、流体力学技術実験装置を用いてマランゴニ対流の観測と制御に関する研究を行う。このTR-1A実験での実験技術開発と臨界実験条件の決定のため、1991年5月、航空機によるパラボリックフライト予備実験を行った。MU-300ジェット機での微小重力条件のもとで、形成した液柱においてマランゴニ対流を観測した。試料液体としてシリコーンオイル(KF-56:15cst)を用いた。液柱形成技術を開発した。速度場観測用アルミニウム微粉末の最適濃度および温度場観測用液晶の濃度を決定した。本予備実験の研究結果はTR-1A実験の有効資料となった。, At the second launch of sounding rocket experiment TR-1A (Test Rocket-1A) (1992), observation of Marangoni convection and its control will be performed with fluid dynamics technology experiment apparatus. In order to develop the experimental technique and to determine the critical experimental conditions for the TR-1A experiment, the preliminary parabolic flight experiments were carried out in May 1991. During the microgravity conditions on the MU-300 jet plane, Marangoni convection in a liquid bridge was observed. Silicone oil (KF-56: 15cst) was used as a test liquid. The technique of making liquid bridge was developed. The most suitable concentration of aluminum particles to observe the velocity field, and the concentration of liquid crystals to observe the temperature field were determined. The results of this preliminary study are very valuable for the TR-1A experiment., 資料番号: AA0000738004, レポート番号: NASDA-TMR-960021

自由界面上の濃度差により発生するマランゴニ対流を活用することにより、化合物半導体の均一混合化技術を確立することを目的として、濃度勾配により生じる真のマランゴニ対流を明らかにし、化合物半導体融液の相互分子拡散係数を求め、さらにマランゴニ対流による混合と分子拡散のみによる混合とを比較するために、地上および微小重力下において、In-Sb(M-1, D-1)とIn-GaSb-Sb(M-2, M-3,M-3', D-2)の計6個の試料を急速に溶融、冷却した。In-Sb系の場合、宇宙で成長した試料について、M-1はほとんど球形であり、またM-1とD-1の双方とも溶融時間が長かったために混合した。一方、地上で成長したD-1は、重力偏折のために、Inの濃度が下方に向かう増加がみられた。均一な濃度分布を持つ結晶は微小重力下で得られることが確認された。In-GaSb-Sb系の場合、宇宙で成長した試料について、M試料は、完全な球形ではないが、丸みを帯びた。Sb側の形状はIn側と比べより収縮した状態となった。結晶中の濃度分布はほとんど均一であった。一方、宇宙で成長したD-2試料の濃度分布は均一でなく、拡散過程が進行していた。濃度差によるマランゴニ対流の活用は、多元系化合物半導体の混合に対し、非常に有効であることが判明した。, In order to develop a new technique for uniform mixing of the compound semiconductors utilizing Marangoni convection due to the concentration difference on the free interface, and to clarify the real Marangoni convection induced by concentration gradient, to obtain counter molecular diffusivity of molten compound semiconductors, and to compare mixing by Marangoni convection with that by molecular diffusion only, 6 type of samples composed of In-Sb (M-1, D-1) and In-GaSb-Sb (M-2, M-3, M-3', D-2) were melted and cooled rapidly under normal and microgravity. In case of In-Sb system, for space grown samples, M-1 samples was almost sphere, and both M-1 and D-1 were mixed because of long dissolution time. On the other hand, D-1 samples grown on the ground, In concentration increased downward because of gravity segregation. It was confirmed that the crystal with uniform concentration distribution can be obtained under microgravity conditions. In case of In-GaSb-Sb system, for space grown samples, M samples became round although they were not complete sphere. The shape of Sb side was more shrunk compared with that of the In side. The concentration distribution in the crystal was almost uniform. On the other hand, the concentration distribution of D-2 samples grown in space was not uniform and diffusion process was on the way. It was pointed out that the utilization of Marangoni convection due to the concentration difference is very useful for the mixing of multicomponent compound semiconductor., 資料番号: AA0000271015, レポート番号: NASDA-TMR-960004

水平管型ホットウォールAPCVD反応器を用い, 酢酸亜鉛を原料としてZnO薄膜を合成した.反応温度473～773K, 全流量250～750sccm, 酸素濃度0～50mol%の範囲内で, 成膜条件による配向性および成膜速度の相違を実験的に検討した.本実験の全範囲内でC軸配向性が見られる.しかし低温で合成した膜はC軸配向性が熱的に不安定である.673K以下の実験ではミクロトレンチ上でステップカバレッジの良い膜が得られ表面反応速度が遅い事が分かった.一方723Kでは, ステップカバレッジが悪化しており, 低温域とは異なる反応機構が発生すると推定された.673K以下での成膜が表面反応速度律速であると考え, 実験で得られた管軸方向の成膜速度分布を最もよく再現する表面反応速度定数を定めた.この方法で得られた表面反応速度定数の活性化エネルギーは, 無酸素時は63KJ/mol, また酸素濃度50mol%の場合は23KJ/molであった.

水平管型ホットウォールCVD反応器を用い, Zrのβ-ジケトン錯体を原料としてZrO2膜を合成した。反応温度823K～973K, 操作圧0.4kPa～24kPa, 全流量0～1500sccm, 酸素濃度0～50mol%の範囲内で, 成膜条件による膜色, 結晶形および成膜速度の相違を実験的に検討した.気相反応速度定数のみを未知パラメータとして含む基礎方程式群の2次元数値計算をZr (DPM) 4を原料とする上記LPMOCVD系に適用し, 実測したすべての管軸方向成膜速度分布をフィットし得る唯一の気相反応速度定数を決定した.活性化エネルギーとして140kJ/mol程度の値が得られた.正PCVD装置を用いるこの種の解析では, 管内圧力損失が無視し得ないことを示した.

Experimental study on thermocapillary convection of low Prandtl number fluid was carried out to estimate the mode structure after the onset of oscillatory flow. The half-zone liquid bridge of molten tin was used as a experimental configuration. In order to detect very slight temperature changes, the temperature measurement system was improved. Temperature oscillations at the interface between liquid and cold rod were obtained by several thermocouples. The first transition could be detected and the transition processes have been clarified. The mode structure appeared in a low frequency oscillation region after the onset was presumed from the phase differences among them. The mode structure was supposed to be 2 and rotation with a frequency of 0.008 Hz. Furthermore, the rotation of the temperature field was elucidated through the multipoint measurements. In addition to above experiment, the preliminary test to visualize the flow field by using ultrasonic wave was performed. The result demonstrates us to be able to visualize the internal flow filed in low Prandtl number liquid column., 資料番号: AA0049790000, レポート番号: JAXA-RR-05-023E

第22回宇宙利用シンポジウム(2006年1月17日-19日, 日本学術会議6階会議室 六本木、東京), The Twenty-second Space Utilization Symposium (January 17-19, 2006: Science Council of Japan, Roppongi, Tokyo, Japan), This report was described the activity of a research working group on Interfacial Phenomena and fluid instability. Primary three themes which would promise to utilize the microgravity condition were discussed. The research plan and organization concerning these themes were established. We start the preparatory study to accomplish each objectives., 形態: カラー図版あり, 共催: 日本学術会議, 著者人数: 11人, Physical characteristics: Original contains color illustrations, Meeting sponsors: The Science Council of Japan, The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (ISAS)(JAXA), 資料番号: AA0064113019

第22回宇宙利用シンポジウム(2006年1月17日-19日, 日本学術会議6階会議室 六本木、東京), The Twenty-second Space Utilization Symposium (January 17-19, 2006: Science Council of Japan, Roppongi, Tokyo, Japan), The experimental study on thermocapillary convection in the liquid bridge of low Prandtl number fluid was carried out. The half-zone liquid bridge of molten tin was used as test configuration. So detect the transition process of oscillatory flow of Marangoni convection in relatively high Marangoni number of 430. In addition to gather from experimental results that oscillation mode., 共催: 日本学術会議, Meeting sponsors: The Science Council of Japan, The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (ISAS)(JAXA), 資料番号: AA0064113026

The experimental study on thermocapillary convection in the Half-Zone Liquid Bridge of low Prandtl number fluid was carried out. The Half-Zone Liquid Bridge of molten tin was used as test configuration. In order to detect the minute temperature fluctuation at second critical point, the temperature measurement system was improved. The behavior just after the onset of oscillatory convection was clarified., 資料番号: AA0048095031

The experimental study on thermocapillary convection of low Prandtl number fluid was carried out to investigate the transition behavior to oscillatory flow. The half-zone liquid bridge of molten tin was used as a test fluid. It can be detected that the steady thermocapillary convection changes to oscillatory under certain condition. It could be experimentally detected that a slow oscillation (approximately 0.02 Hz) appeared after the onset of oscillatory flow, and then the oscillation became faster (approximately 0.3 Hz) when the temperature difference increased. As for the experimental result, it matched the circumstance of the temperature vibration in the transition process of the thermocapillary convection which is expected with numerical simulation well., 資料番号: AA0046917049