Development of a Method to Estimate the Dispersion and Knudsen Diffusion Coefficients in Soil by Using the Dusty Gas Model

Abstract

2 名城大学 理工学部環境創造学科（〒468-8502 愛知県名古屋市天白区塩釜口1-501） 土中ガス中の多成分物質移動にDusty Gasモデルが有効であることは，これまでの研究で知られている． しかし，Dusty Gasモデルから分子拡散係数，Knudsen拡散係数，屈曲度と機械的分散係数を求める方法は 確立されていない．そこで，本論文では，2成分のDusty Gasモデルを基にこれらの定数を求める方法を開 発した．その際に，土壌中の2成分の境界で流速と分散係数の変化を考慮できるように，特性曲線型有限 要素法で定式化された移流分散方程式にPowellの共役方向を適用した逆解析プログラムも開発した．本研 究で行った2成分の一次元カラム実験結果に逆解析プログラムを適用して得られた合成分散係数と合成流 速，および今回開発した手法を用いることによりこれらの定数を求めることができることが分かった．

Method for obtaining the Knudsen diffusion coefficient

“…Although for this fitting we used the ISCCFEM-adq inversion simulator developed by Hibi and colleagues [6,7], which employs a conjugate direction method [8] and a characteristic finite element scheme [9], any general inversion simulator for the advection–diffusion equation can be employed to obtain the effective compound diffusion coefficients and the effective compound velocities of the tracer gases from tracer experiment results.…”

“…The effective compound diffusion coefficients and the effective compound velocities of two tracer gases (gases A and B) are obtained by using an inversion simulation to fit the advection–diffusion equation to the experimentally determined distribution of the molar fraction of each tracer gas. Although for this fitting we used the ISCCFEM-adq inversion simulator developed by Hibi and colleagues [ 6 , 7 ], which employs a conjugate direction method [ 8 ] and a characteristic finite element scheme [ 9 ], any general inversion simulator for the advection–diffusion equation can be employed to obtain the effective compound diffusion coefficients and the effective compound velocities of the tracer gases from tracer experiment results.…”