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不飽和多孔質媒体内の流れは，水と空気の2相流れの問題となる。本研究では間隙内空気の流れの効果を考慮するために，多相流理論に基づき水と空気の2相流モデルの導入を行った。これまで天然ダムの斜面の安定解析では，突然の決壊を予測するために，間隙水圧と含水率を解く従来の水相流モデル，水と空気の2相流モデルによって解析されており，そのモデル内はJanbuの簡易的な方法だけでなく，平衡状態に基づいた拡張Spencer法などが用いられている。本研究では，拡張Spencer法を用いて2相流れを解析しており，実験結果とも比較的良く一致した結果が得られている。, Water flow in unsaturated porous media is water- air two-phase flow problem. To incorporate the effect of pore air flow in the soil seepage analysis a water-air two-phase flow model, based on the multi-phase flow theory is used. Slope stability analysis of land slide dam has been carried out using pore water pressure and moisture content calculated by only a conventional water-phase flow model as well as the water-air two-phase flow model so as to predict the failure of dam due to sudden sliding. Janbu's simplified method as well as extended Spencer method based on limiting equilibrium considerations is used in slope stability analysis. Overall simulation results obtained by considering two-phase seepage flow combined with extended Spencer method of slope stability analysis are comparatively in good agreement with the experimentally observed results.

Heat generation density from semiconductor devices increases with the rapid development of electric technology. The cooling system using boiling two-phase phenomena attracts much attention because of its high heat removal potential. The technology can be applied to the cooling systems in space. Experiments on the increase of CHF (Critical Heat Flux) for flow boiling in narrow channels by improved liquid supply were conducted for the development of high-performance space cold plates. A structure of narrow heated channel between parallel plates with an unheated auxiliary channel was devised and tested by using water for different combinations of gap sizes and volumetric flow rates. Three kinds of liquid supply methods were conducted and the data were compared. CHF values of 2 x 10(exp 6) W/sq m were obtained for the improved configuration. One of liquid supply methods, where liquid is supplied to both of the main heated channel and the auxiliary unheated channel keeping the exit of the auxiliary unheated channel closed, obtains the highest CHF at total volumetric flow rate more than 1.80 l/min and for a gap size of 2 mm., 資料番号: AA0063706049

Boiling heat transfer enhancement is efficient for development of a cold plate used in a two-phase flow loop type thermal control system. This study deals with boiling heat transfer enhancement for a narrow channel by thermal spray coating. Copper particles were coated on the heating surface by vacuum plasma spraying. Two kinds of surface were manufactured using different particle size, about 200 and 50 micrometer. The heat transfer performance was evaluated in saturated flow boiling experiments of HCFC123 for ranges of mass flux of 100 to 400 kg m(exp -2) s(exp -1), inlet quality of 0 to 0.60, and heat flux of 25 to 251 kW/sq m. The test channel with the channel width of 20 mm, and heated length of 100 mm was placed horizontally and heated from the bottom by cartridge heaters through a copper block. The channel gap was set to 2 and 4 mm. As the result, the coating surface produced higher heat transfer coefficient than the smooth surface, especially, the heat transfer performance of the surface using finer particle was higher and was about five to 10 times higher than that of the smooth surface. While the effect of gaps on the heat transfer coefficient was a little, the critical heat flux increased with increasing the channel gap., 資料番号: AA0063706054

Investigation of mechanisms in nucleate boiling under microgravity condition is essential for the development of high efficiency thermal management systems in space. A transparent heating surface with multiple arrays of 88 thin film temperature sensors and mini-heaters was developed for the clarification of boiling heat transfer mechanisms in microgravity through the investigation of the relation between local heat transfer coefficients and behaviors of liquid microlayer underneath vapor bubbles. Pool boiling experiments in microgravity by ESA parabolic flight campaign are planned using the heating surface developed. A description of the experimental setup, methods, conditions and the expected results in the aircraft experiments are presented., 資料番号: AA0063706050

Development of thermal management systems handling a large amount of waste heat and its long distance transportation becomes a key technology required for the long-term operation of large space platforms and of manned spacecraft systems. Boiling and liquid-vapor two-phase systems are powerful means for the present objectives and both of fundamental and applied experiments utilizing long-term microgravity opportunity are required. In the present paper, a concept for the proposal of systematic experiments is described., 資料番号: AA0063706030

It is essential to develop gas-liquid two-phase flow (gas-liquid concurrent flow) modeling not only for improved heat transfer efficiency in territorial energy plants but also for the design of fuel pipe flows and heat control lines in spacecraft. Many experimental and theoretical efforts have been devoted to achieving a two-fluid model, which is one of the most popular models for industrial use. Such a model consists of individual mass, momentum, and energy conservation equations for two-phase flow, using an accurate description of the interfacial area transport or interfacial area concentration and the drive force acting on the gas-liquid interface. In this research, a basic database was obtained by measuring interfacial area transport under micro- and normal-gravity environments, using the drop-shaft in the Micro-Gravity Laboratory of Japan (MGLAB). The database showed the proposed model accurately predicted the relative velocity between bubble and liquid flow in the channel even in micro-gravity condition, and the estimated weight caused by the frictional pressure loss should be taken into account in the interfacial area transport and drift velocity., 資料番号: AA0063349020

In cryogenic fluid, such as rocket propellants, thermal effect has to be properly treated, which is usually neglected in common fluids. In the present study, a cavitating flow solver, which is based on bubble two-phase flow model including energy equation, was constructed and flow calculation was carried out around 2D NACA0015 airfoil. Comparison between water and liquid nitrogen reveals that cavitating pattern between these two fluids are completely different and this difference was raised from thermal effect of cryogenic fluid. The effect of numerical dissipation was also discussed to reveal that excess numerical dissipation affected the cavitation very much, consequently, cavitation performance became completely different from that due to the higher-order calculation., 資料番号: AA0045948032, レポート番号: NAL SP-57

以下の主題を論じた。能動振動システム、気泡の形成と運動、ガラスの溶融・凝固実験、対流-凝固実験、2相流動実験、および空酔い。, The following topics were discussed: active vibration isolation system, bubble formation and motion, melt and solidification experiment of glass, convection solidification experiment, two phase flow experiment, and air sickness., 資料番号: AA0000739000, レポート番号: NASDA-TMR-960022

The Earth is likely experienced magma ocean stage during accretion. One issue of debate is whether or not differentiation of silicate mantle proceeds in a deep magma ocean. To investigate this problem I calculated thermal and chemical evolution of magma ocean using a one-dimensional two-phase-flow heat and mass transfer model. Differentiation at the lower mantle pressure may not proceed, if no atmosphere exists. On the other hand, if the blanketing effect of the atmosphere prevents efficient cooling, differentiation in the lower mantle should proceed., 資料番号: AA0063352030

気泡を含む液体の中の定常および非定常の弱い衝撃波を数値的に扱う。気泡を含む流れを記述する新しいモデル方程式系を適用して衝撃波面の下流の流れの構造を詳細に調べた。気相と液相の間の泡の表面を通した熱伝導は衝撃波面近傍の波形に著しく影響すること、また、弱い衝撃波に対しては気相と液相との間の速度差が波形に影響すること、などが示された。泡の大きさの振動的変化は混相流の圧力プロファイル、特に波面近傍における流れの圧力プロファイルにおける振動をひき起す。数値シミュレーションによれば、弱い衝撃波は波面の近傍の先行波とその下流の主成分波とから成る。ポリトロープ指数を一定としたモデルに関わる定常衝撃波は、低圧部および高圧部がそれぞれ一様な条件にあるとした場合の衝撃波管問題の漸近解として実現される。, Steady and unsteady weak shock waves in a bubbly liquid are treated numerically. A new system of model equations describing the bubbly flow is applied and the flow structure behind a shock front is investigated in detail. It is shown that the heat conduction between the liquid and the gas phases through the bubble surface affects significantly the wave profile near the shock front. It is, however, shown that the velocity difference between the liquid and the gas phases affects the wave profile remarkably for weak shock waves. Radial oscillation of bubbles tends to produce oscillatory profile of the mixture pressure especially near the wave fronts. Numerical simulation shows that the weak shock consists of a precursor near the shock front and a main shock downstream of it. It is confirmed that the stationary shock wave for a constant polytropic-exponent model is realized as an asymptotic solution for a shock tube problem with uniform conditions in the low pressure and high pressure chambers., 資料番号: AA0004174022, レポート番号: NAL SP-27

航空宇宙技術研究所 10-11 Jun. 1993 東京 日本, National Aerospace Laboratory 10-11 Jun. 1993 Tokyo Japan, ラバールノズル内を流れる気泡流の特性を理論的および数値的に調べた。分散気泡相を支配する新らしいモデル方程式を提案し、以前に提案したものとの比較を行う。次に、得られた支配方程式系の双曲性を詳細に調べた。この提案されたモデル方程式系を用いて、ラバールノズル内の気泡流の数値シミュレーションを行った。数値計算結果、従って提案された方程式系、の妥当性を調べるため、水と窒素ガスを使った吹出し風洞における実験と比較した。, Characteristics of bubbly flow through a converging and diverging nozzle are investigated theoretically and numerically. First, a new model equation of motion governing a dispersed bubble phase is proposed. This is compared in detail with those proposed previously. Next, hyperbolicity of the resultant system of governing equations for the bubbly flow is investigated in detail. Numerical simulation of bubbly flows through a converging and diverging nozzle are carried out by using the proposed system of model equations. In order to check the validity of t numerical results and then the proposed system, they are compared with the experiments which were performed in a water-nitrogen blow-down facility., 資料番号: AA0004171016, レポート番号: NAL SP-22

近年、宇宙ステーションの大規模化に伴う内部の熱処理問題や、宇宙における太陽発電システム(SSPS)の各変換部の冷却など、宇宙における排熱技術に対するニーズが高まっており、潜熱利用流体ループ排熱システムが注目されている。このシステムは流体の潜熱を利用して熱輸送を行うためにシステムの重量が軽減でき、圧力を操作することによって飽和温度を制御するため、素早く正確な制御が可能である。しかし、その制御技術は未だ確立されておらず、実用化に至っていない。本研究では、蒸発器と凝縮器を繋ぐ配管部に流量調節バルブを設置し、その開度を変えることで圧力を制御し、システムの過渡応答特性を実験で調べた。また、プログラムによってバルブを自動制御し、熱負荷急変に対してループ制御の可能性を探り、以下の結果が得られた。1)蒸発器出口クォリティが高いほどバルブ操作に対する圧力変動の幅が大きく蒸発器表面温度の変化も大きい。2)蒸気配管部に設置したバルブを開操作することで、バルブでの圧力損失および蒸発器圧力が減少し、蒸発器表面温度が低下した。3)蒸気配管部に設置したバルブを閉操作することで、バルブでの圧力損失および蒸発器圧力が増加し、蒸発器表面温度が上昇した。4)流量が小さいほどサブクール沸騰から飽和沸騰に移行する位置が早く、熱貫流率の上昇速度も大きい。また、熱貫流率が大きいほど熱移動が行われやすいため、蒸発器表面温度の遅れ時定数が小さい。5)作動流体流量を手動で一定に保つことで安定な応答が得られるが、流量調節を行わなくても熱移動が行われ、制御対象を1つ減らせるので流量調節の必要はないといえる。6)バルブにプログラマブルコントローラを設置し、コンピュータプログラムによってバルブを自動制御し、蒸発器表面温度を一定温度幅内に保持することは可能である。, 資料番号: AA0047683000, レポート番号: JAXA-CR-04-002

近年の宇宙構造物の大規模化に伴う排熱量増大や、宇宙太陽発電システム(SSPS)の各変換部の冷却など、宇宙における排熱技術に対するニーズは高まっており、潜熱利用流体ループ式排熱システムが注目されている。このシステムは蒸発潜熱を利用して熱を吸収し、輸送するため、ポンプ動力やシステム重量を軽減できるメリットがある。また、圧力により作動流体の飽和温度を制御できるため素早く正確な制御が可能であるが、その制御技術は未だ確立されておらず実用化に至っていない。本論文では、潜熱利用流体ループ式排熱システムの動特性の把握を目的に、熱負荷、作動流体流量などの各種パラメータ変化に対する動特性実験を行った。さらに、従来の研究に無い新しいバルブ操作による制御方式を提案する。次に、動特性実験と同時に、本システムの動的シミュレーションモデルを構築し数値解析を行い、実験結果と比較検討した。これらの実験・数値解析より、以下の結果が得られた。1)熱負荷変化に対する蒸発器表面温度変化の一次遅れ時定数は低クォリティ領域では作動流体のクォリティに左右され、サブクール沸騰領域で極端に時定数が大きく、遅い。2)作動流体流量を操作する事は、潜熱利用流体ループ式熱制御システムの熱源温度を制御する方法としては不適当である。3)アキュムレータ圧力変化に対する蒸発器表面温度変化の一次遅れ時定数は低クォリティ領域では作動流体のクォリティに左右され、サブクール沸騰領域で極端に時定数が大きくなる。4)バルブを操作する事でEV圧力およびEV表面温度は一次遅れ状に変化する事が確認できた。5)蒸気バルブ開度操作により、潜熱利用流体ループ式排熱システムの熱源温度を自動的に一定範囲に制御する事が可能である事が検証できた。6)数値解析結果は実験結果と良く一致し、潜熱利用流体ループ式排熱システムの動的シミュレーションヘの適用可能性が確認できた。, 資料番号: AA0047682000, レポート番号: JAXA-CR-04-001

In relation to the development of the interfacial area transport equation, axial developments of void fraction profile, interfacial area concentration and Sauter mean diameter of adiabatic nitrogen-water bubbly flows in a 9 mm-diameter pipe were measured by using a stereo image-processing method at normal- and micro-gravity conditions. The effect of gravity on radial distribution of bubbles and the axial developments of two-phase flow parameter was discussed in detail based on the obtained data and the visual observation., 資料番号: AA0063706038