水の密度逆転領域を含む自然対流と凍結・融解の多相場数値解法

Abstract

本研究では，密度逆転領域を含む自然対流を伴った水の凍結および氷の融解問題に対し，相平均モデルに基づく多相場数値解法を適用した．凍結・融解モデルについては，固液界面におけるステファン条件の計算手法を改良し，計算セル内における界面位置を考慮して凍結層厚さを計算する方法を提案した．１次元の凍結問題を計算して提案手法の基礎的検討を行った後，矩形領域内における非定常凍結問題および非定常融解問題を計算した．その結果，計算により得られた固液界面位置の変化が既往の実験結果によく一致することが示された．また，密度逆転を伴う自然対流についても適切に計算されることが示された．

A multiphase computation method based on the phase-averaging method was applied to water-ice phasechange problems accompanied by the natural convections including density inversion regions in water. The computation method for the Stefan condition was improved in this study to calculate the freezing thickness considering the position of the water-ice interface in the computational cells. After the basic verification of the proposed method using the one-dimensional freezing problem, the experimental results of the unsteady freezing problems and those of the unsteady melting problems in rectangular cavities were calculated with the present method. As a result, it was shown that the changes in the calculated water-ice interfaces are in good agreement with the experimental results and that the natural convections with density inversion are reasonably calculated.