Since a thin radial liquid film flow on a stationary and rotating disk has the velocity profile of a boundary layer, a remarkable transition from laminar to turbulent flow occurs at a sufficiently large Reynolds number, being attributable to the amplification of disturbance inside the liquid film. The instability of the flow changes from a viscous-to an inflectional-type with increasing effect of the disk rotation on the flow. The former instability is essentially the same as that of the boundary layer on a flat plate in a stream, whereas the latter is similar to that of the three-dimensional boundary layer on a rotating disk in still fluid. In the present article, the feature of liquid surface in the transition region and characteristic properties of the disturbance detected through wall pressure fluctuation are reviewed in comparison with the linear stability theory.

抄録全体を表示

In the present work, the two-dimensional turbulent liquid-particle flow around a blade-to blade surface of a centrifugal impeller has been simulated by using a two-phase turbulence model, that is, the k-ε liquid turbulence model and the algebraic particulate phase flow turbulence model. The interaction between the liquid phase and the solid phase has been considered in the conservative momentum equations of the two-phase flow. Calculated results show that the turbulence model can predict essential features of the complex liquid-particle flow through the impeller.

抄録全体を表示

In the previous study, the numerical stability of high-order upwind schemes adopted to the two-fluid model was systematically evaluated using a single linear model equation of the two-fluid model. It was demonstrated that the inclusion of an explicit diffusion term in the basic equation can remove the numerical instability when the high-order upwind scheme is used. However, it was not confirmed if these results were applicable to the two-fluid model since the model equation used cannot represent the characteristics of the two-fluid model perfectly. In this study, high-order upwind schemes were applied to the actual two-fluid model and the numerical stability under various conditions was examined. The results for the two-fluid model correspond well to those predicted by the model equation. Hence, it was confirmed that the numerical stability of the two-fluid model can be examined qualitatively with the linear model equation. It was also confirmed that the explicit diffusion term is effective for the two-fluid model calculation with the high-order upwind scheme.

抄録全体を表示

An experimental study has been conducted to investigate the mechanism of liquid film transport in horizontal annular flow by visualizing the motion of the liquid film on the inner tube wall using a photochromic dye activation method. The captured motion clearly reveals spreading of the liquid during the passage of disturbance waves and constant drainage of the liquid film after the passage of the disturbance waves. The present results support the liquid transport mechanism due to the pumping action of the disturbance waves proposed by Fukano and Ousaka rather than the secondary gas flow or surface wave mechanisms proposed by Laurinat et al. and Jayanti et al.

抄録全体を表示

固気二相流中を運動する粒子が粒子間衝突の影響を受けるような流れをラグランジュ型の数値シミュレーションで取り扱おうとする場合に、希薄気体の流れの計算に用いられるDSMC法 [1] は粒子間衝突の有力な計算法として期待できる。本講座はそのような立場からDSMC法の基礎とその固気二相流への応用について述べるものである。前回 [2] はその1回目として、固気二相流中での粒子間衝突の影響と、DSMC法を理解するために必要な分子気体力学の基礎概念について述べた。今回はそれに引き続いて、DSMC法で用いられるモンテカルロ法の手法とDSMC法について解説を行う。

抄録全体を表示