Nonzero-Concentration Boundary Condition for Advection-Diffusion Aerosol-Transport Modeling
Nonzero-Concentration Boundary Condition for Advection-Diffusion Aerosol-Transport Modeling
复制标题
平流扩散气溶胶输运模拟的非零浓度边界条件
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
D. Rader
中科院分区：
文献类型：
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作者：
M. Gallis;J. Torczynski;D. Rader
引言这篇简短的通讯介绍了最近的结果有关的对流扩散输运模型的纳米粒子气溶胶。虽然在其他地方进行了详细讨论（Gallis et al. 2008; Torczynski et al. 2008），但为了方便气溶胶科学和技术读者，在此简要总结了这些结果。在气溶胶传输模型中，壁面附近的颗粒浓度（气体中的数密度）几乎普遍被认为是零（Friedlander 2000）。这种近似对于环境空气中常见的气溶胶颗粒非常好。然而，对于目前实验中使用的直径为20 nm的标准化纳米颗粒（Kim et al. 2005），在某些情况下，这种近似值可能变得不太准确（Gallis et al. 2008）。而不是消失在一个壁，浓度接近一个非零值成比例的粒子通量的墙壁，即使是在概率的影响粒子坚持是统一的。只有当基于热速度的颗粒停止距离与几何长度尺度相当时，这种效应才是显著的，这发生在大气压下的微米尺度几何形状中的纳米颗粒气溶胶或成比例地较低压力下的较大几何形状中的纳米颗粒气溶胶。
INTRODUCTION This Brief Communication presents recent results related to advection-diffusion transport modeling of nanoparticle aerosols. While discussed elsewhere in detail (Gallis et al. 2008; Torczynski et al. 2008), these results are summarized briefly here for the convenience of Aerosol Science and Technology readers. In aerosol-transport modeling, the particle concentration (number density in the gas) adjacent to a wall is almost universally taken to be zero (Friedlander 2000). This approximation is extremely good for commonly encountered aerosol particles in ambient air. However, for standardized nanoparticles with diameters of 20 nm now used in experiments (Kim et al. 2005), this approximation can become less accurate under certain circumstances (Gallis et al. 2008). Instead of vanishing at a wall, the concentration approaches a nonzero value proportional to the particle flux to the wall even when the probability that an impacting particle sticks is unity. This effect is significant only when the particle stopping distance based on the thermal velocity is comparable to the geometric length scale, which occurs for nanoparticle aerosols in microscale geometries at atmospheric pressure or in larger geometries at proportionally lower pressures.