論文

An approximate mapping method was applied and validated to predict the mixing state of an oscillatory baffled reactor in the low oscillatory Reynolds number regime. In addition, a fractal dimension method using mapping images for mixing performance evaluation was validated. The Poincaré maps approximated by Shepard's method were employed for the predictions. The results were well-matched when comparing fluid deformation and the mixing performance with the mapping method and direct numerical calculations based on virtual particle tracing, with the relative error being small at less than 1.5%. Using the mapping method, the computational time required for CFD was reduced, and the total time for the entire process up to the evaluation of mixing performance was reduced to two-thirds. Moreover, the results of the mixing performance evaluation using the fractal dimension were consistent with those obtained from a standard method. It was shown that the mixing performance evaluation through simple image analysis, based on the mixing enhancement mechanisms of laminar flow, is feasible.

The mixing mechanism in an oscillatory baffled reactor (OBR) at the low oscillatory Reynolds number was analyzed using numerical simulation. OBR is a tubular reactor in which baffles are placed at equal intervals, and the interaction between the baffles and oscillatory flow mixes the fluid. At the low oscillatory Reynolds number, mixing induced by the folding and stretching of the fluid was observed at each baffle section. This was caused by the radial flow in the vicinity of the baffles when the direction of the oscillatory flow was reversed. The mixing performance was quantified by applying virtual particle tracing, setting up a virtual boundary surface, and following the changes in its area over time. The area increased exponentially, confirming the chaotic mixing characteristics.

発熱反応を伴う剪断流動場において反応による局所的な物性の変化により二流体の境界付近で生じる振動現象について解析した.流動パターンの可視化実験を行い装置形状,操作条件および流体物性が流れの振動パターンに及ぼす影響について検討し,フラクタル次元を用いて振動パターンの複雑性を定量化した.また,熱移動の振動による温度変動パターンについても同様にフラクタル次元を用いた複雑性の定量化を行った.さらに,振動発生機構についてペトリネットによるモデル化とシミュレーションを行った.