混相流

界面活性剤により形成される棒状ミセルのレオロジーと乱流制御効果

薄井洋基

1997 年 11 巻 1 号 p. 3-6
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.3

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The addition of cationic surfactants with suitable counter ion causes a remarkable drag reduction in a turbulent pipe flow. This drag-reducing technique is one of the candidates for pumping power reduction in a district heating and cooling system. Since the scale of micelles formed by surfactant additives is very small, the dynamics of rod-like micelles in a turbulent flow field can not be detected at the present stage. Also, the theoretical prediction of the movement of a rod-like micelle as a two phase turbulent flow is very difficult. The configuration of rod-like micelles and the viscoelasticity caused by the rod-like micelles are reviewed. Recent approaches to the theoretical prediction of surfactant drag reduction mechanism are also reviewed. These information reveals out the present status of drag reduction phenomenon from the stand point of multiphase flow.

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液体ロケットエンジン

岸本健治

1997 年 11 巻 1 号 p. 7-10
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.7

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Liquid propellant rocket engine is introduced, and discussed about the technology status. As a relation with Multiphase technology, a new rocket engine development approach is introduced.

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地熱開発と混相流

木村繁男

1997 年 11 巻 1 号 p. 11-14
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.11

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Multiphase flows that arise in geothermal energy development have been briefly reviewed. A particular emphasis is placed on gas-liquid two-phase flows in geothermal production well. A liquid phase geothermal fluid is normally fed at the bottom of the well. However, as the fluid rises in the wellbore, it loses the pressure and eventually starts boiling; a steam-water two-phase flow results. A one-dimensional formulation of the two-phase flow for wellbore simulation is described in some detail, where the steam-water relative velocity is taken into account through empirical correlations. The presence of dissolved NaCl and noncondensable gas (CO₂) is. one characteristic of geothermal fluid. The present status of two-phase flow simulators for production wellbore is also described. It is suggested that the empirical correlations to differentiate flow regimes and to evaluate the frictional pressure losses along the well, especially for large diameter pipe flows, are essential in accurate prediction of the wellbore two-phase flows.

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製剤装置内粒子流れの数値シミュレーション

六車嘉貢

1997 年 11 巻 1 号 p. 15-18
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.15

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Numerical simulation of the particulate flows has become possible by using discrete element method (DEM) with high performance computers. Calculations of particle motion in three kinds of pharmaceutical apparatus done by the author are reviewed. A centrifugal tumbling granulater, a rotating vessel type mixer and a screw feeder are dealt with. The present simulations predict well the realistic particulate flows. Pharmaceutical industries manufacture products which affect human life. Therefore it is necessary to make the process validation which guarantees the security of life and the effect of a medicine. It is important to know the behavior of particles in detail in order to control the quality 01 pharmaceuticals. The numerical simulation makes it possible to know the detailed information such as the three dimensional particle behavior, the interaction between particles and the effect of condition of equipment. These information is helpful in deepening out understanding powder processes.

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船舶と混相流

児玉良明

1997 年 11 巻 1 号 p. 19-22
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.19

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Flows around ships have various kinds of multiphase flows because ships move at the interface between air and water. The first example is free-surface waves generated by an advancing ship. The phenomenon can be simulated using CFD based on NS solvers, and the comuted wave pattern and the wavemaking resistance agree well with measurements. The second example is wave impact generated at the bow of a ship running in waves. In this example, the flow becomes a multiphase flow type with foams or bubbles. The third example is propeller cavitation, which is an evaporation process at normal temperature. On a full-scale propeller, the cavitation consists of bubbles, which cause erosion in the collapsing stage. The last example is microbubbles for the reduction of frictional drag, the major part of ship's drag. The microbubbles are quite effective in the reduction, but further study is needed for its practical use.

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マルチフィラメント糸のインターレース空気加工

家元良幸

1997 年 11 巻 1 号 p. 23-29
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.23

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The processing mechanism, structure and property of multiple filament interlaced yarns with alternate tangling and opening parts are described on the basis of experimental data. The most important factor in the interlacing process is an air flow in a yarn duct of an interlacer. The high speed turbulent air jetting into the yarn duct from an air jet nozzle opens multiple filaments of running yarns separately and changes their relative positions. An opening part is formed at the position subjected to the air jet directly and tangling parts are formed at its both ends. The tangling parts keep their forms by the friction among filaments although the tangling part formed before the air jet nozzle is directly subjected to the air jet. Filaments in the tangling parts contact with each another and the number of tangles depends on the processing conditions of the working air pressure and feed ratio.

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粉粒体・ガス系の流動層のエマルジョン相の性質の基本的問題

古典としてのDavidsonの二相流理論の限界とその物理的意義および最近のエマルジョン相の流動特性の研究

河野尚志

1997 年 11 巻 1 号 p. 30-36
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.30

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A review on the classical two phase flow theory is carried out in this paper, based on the updated theories and experimental works of the 1990s. Recent developments of the emulsion phase characterization methods using powder rheology in fine powder fluidized beds are introduced and reviewed. Particularly, the physical meaning and significance of incipient bubbling points are interpreted in terms of the fracture model. The significance of flow characteristic functions of aerated fine powders, obtained theoretically and experimentally, is explained.

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直接混合軸流サイクロン型ガスー粒子間熱交換器の研究

第1報: 熱交換器の提案と固気分離性能

横峯健彦, 清水昭古, 永渕竜朗, 中村光宏

1997 年 11 巻 1 号 p. 37-45
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.37

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A direct mixing type axial flow cyclone heat exchanger between gas and high temperature particles is proposed which serves as particle separator as well. The proposal was motivated by the concept of high temperature nuclear energy conversion system for which dense gassolid suspension flow is considered as primary coolant. However, it may also be used as a general heat recovery device from various high temperature powdery waste material from conventional industry. In this heat exchanger, the particles, after being mixed directly with gas, transfer their heat to the gas in the form of quasi-counter-flow and are effectively re-separated by centrifugal force due to swirling motion of the gas. The mock-up of the heat exchanger was designed and constructed and its reseparation performance was examined both experimentally and numerically, which is the key to realize such innovative energy conversion systems.

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ノズルおよびオリフィスからの気泡生成に関する実験的研究

第1報、上向きガス吹込み時の気泡生成頻度

井口学, 千原知幸

1997 年 11 巻 1 号 p. 46-55
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.46

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Gas was injected into a bath vertically upward through a nozzle, an orifice, or a lance nozzle. The frequency of bubble formation at the exit of these injection devices was determined by counting the number of bubbles per second from visual images recorded using a high-speed video camera. The measurements were carried out under the condition that the effect of the gas chamber volume on the bubble formation was negligible. An empirical correlation of the bubble frequency was proposed as a function of gas flow rate, inner diameter of the nozzles and orifices, and the physical properties of gas and liquid. This correlation could estimate measured values of the frequency of bubble formation even for a high gas flow rate within a scatter of ±30% regardless of the injection devices.

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LN₂自然循環系における流動脈動時の限界熱流束

梅川尚嗣, 小澤守, 石田直樹

1997 年 11 巻 1 号 p. 56-65
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.56

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In a natural circulation loop, flow instability, such as density wave oscillation, occurs under a certain operating condition, while the influence of flow oscillation on the heat transfer is not well understood so far. Experiment was conducted by using a natural circulation loop of liquid nitrogen with test tubes of dimensions of 3.0mm/5.0mm I.D., and 900mm heated length. It was indicated that the heat transfer correlation of Schrock-Grossman was in good agreement with experimental results in the saturated boiling region even under oscillatory flow condition, and that the correlation of Roko was in good agreement with the experimental results of post-dryout heat transfer even under oscillatory flow condition. On the other hand, the CHF was well predicted using the lumped-parameter model, taking account of the circulation rate, oscillation frequency and amplitude of mass flux in the natural circulation loop.

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キャビテーションと気泡力学に関する用語

高比良裕之

1997 年 11 巻 1 号 p. 66-69
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.66

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液体中の圧力が, その温度における飽和蒸気圧程度まで低下すると、気泡が発生する。この現象およびその後の諸過程をキャビテーションと呼ぶ。キャビテーションは、古くから水力機械の性能を考える上で、重要な研究課題となっているが、昨今、キャビテーションは、こうした工学的問題に限らず、物理・化学・医学の分野でも様々な話題を提供している。本報では、キャビテーションに関連したいくつかの用語の説明を行うとともに、気泡力学で用いられる代表的な単一運動方程式を紹介する。

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インピーダンスCTによる気液二相流のボイド分布測定法の開発

隅田勲, 早矢仕英謙, 田中一也

1997 年 11 巻 1 号 p. 70-73
発行日: 1997/03/15
公開日: 2011/02/22

DOIhttps://doi.org/10.3811/jjmf.11.70

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Though impedance CT (Computed Tomography) has been developed for medical applications at first, it is attractive to apply to the measurement of time-averaged void distribution in two-phase flow, because the device is simple and easy to handle. In the impedance CT, the image of void distribution is reconstructed from current signals of electrodes set up in outer boundary of the measurement area. Therefore the point of the development is how to solve the reverse-problem.This paper describes a method based on the neural-network theory to solve this reverse-problem and its verification by comparing with experimental data.

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