ラグランジュ的な粒子速度の関係を用いた2粒子対確率過程モデルによる変動スカラ場の数値シミュレーション

概要

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In this paper, an improved stochastic process model of a particle-pair for the predicting the statistical value of the scalar fluctuation fields in a turbulent flow is suggested. The past other stochastic process models use a Karman-Howarth (Eulerian) relation as a Lagrangian velocity correlation function between the two particles approximately. It looks like a good approximation, but it should be exact neither physically nor mathematically. The main points of improvement are as follows : (1) The Faller's velocity relations of the Lagrangian tracers is used as a Lagrangian velocity correlation (2) The function form of the Faller's velocity relations is expanded to the viscous-dissipation range for the simulation of the low-Reynolds number turbulence. Simulations of two types of scalar fluctuation fields (of a point source plume and of a line source plume in a gridgenerated turbulence) has been made and the simulation results are compared with the experimental data. In both cases, the improved model show a better prediction of the actual scalar fluctuation statistics.
1998-09-25