Dispersion in open-channel flow subject to the processes of sorptive exchange on the bottom and air–water exchange on the free surface
Dispersion in open-channel flow subject to the processes of sorptive exchange on the bottom and air–water exchange on the free surface
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DOI：
10.1016/j.fluiddyn.2006.02.002
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发表时间：
2006-06
影响因子：
1.5
通讯作者：
C. Ng
中科院分区：
文献类型：
--
作者：
C. Ng
分析研究了由于床层的可逆吸附相交换和自由表面上不可逆的空气-水反应而产生的综合效应下稳定和振荡明渠流的分散。假设自由表面反应非常弱，以至于在空气发生过度大量损失之前就可以形成渐近平均浓度。使用多尺度均质化技术导出的有效平流-弥散传输方程包含由两种化学效应产生的弥散系数的各个组成部分的形式表达式。数值计算表明，只要床处于吸附状态，吸附交换动力学在控制整体分散机制中起着关键作用。底部存在动力相交换可以显着增强自由表面损失的微弱影响。
An analytical study is presented of dispersion in steady and oscillatory open-channel flows under the combined effects due to reversible sorptive phase exchange with the bed and irreversible air–water reaction on the free surface. The free-surface reaction is assumed to be so weak that the asymptotic mean concentration can be developed well before undue substantial loss to the air occurs. The effective advection–dispersion transport equation, which is derived using a multiple-scale homogenization technique, contains formal expressions for the various components of the dispersion coefficient arising from the two chemical effects. Numerical calculations demonstrate that, as long as the bed is sorbing, the kinetics of the sorptive exchange plays a key role in controlling the overall dispersion mechanism. The otherwise weak effects of the free-surface loss can be significantly enhanced by the presence of kinetic phase exchange on the bottom.