液滴径分布の変化から衝突頻度因子を導出する線形逆解析手法

摘要

We have developed a new simple inversion scheme for retrieving collision kernels from the change of droplet size distributions due to collision growth. Three-dimensional direct numerical simulations (DNS) of colliding droplets in an isotropic steady turbulence are performed in order to investigate the validity of the developed inversion scheme. In the DNS, air turbulence is calculated using a quasi-spectral method, and droplet motions are tracked by a Lagrange method. The initial droplet size distribution is set to be equivalent to that obtained in a wind tunnel experiment. Comparison between collision kernels retrieved by the developed inversion scheme and those obtained by DNS shows that the collision kernel can be retrieved within 15% error. This verifies the feasibility of retrieving collision kernels by using the present inversion scheme.%気相乱流中で微小液滴が衝突する現象は，蒸気発生器，噴霧器，およびサイクロン分離器などの工業装置内の流れや，鉛直方向に発達する対流雲中に見られる．従って，その衝突挙動を正確に予測することは，工業装置の最適設計・操作，および対流雲とそれに伴う豪雨の高精度予測などに関連して，機械工学的，環境工学的に極めて重要である．