A study on tubulence models for diffusion and absorption of contaminant and carbon dioxide within vegetation

本文提出了两种湍流模型，模拟了污染物和二氧化碳在植被中的扩散和吸收。一个是（k-ε）型模型，另一个是LES（大涡模拟）模型。在（k-ε）模型中，我们采用了先对基本方程进行总体报复，再进行空间平均的方法。采用滤波器进行空间平均。我们假设领带过滤器是足够光滑的，虽然它是礼帽型的。采用整体平均的Navier-Stokes方程，解析地推导了压力和应变引起的阻力。从基本方程出发，推导了湍流能量方程和粘性耗散率方程。模拟了植被对湍流能量方程和粘性耗散率方程的影响，并对方程进行了封闭，通过与实测资料的比较，验证了模型的正确性。对于LES模型，我们采用了充分平滑的顶拍滤波器。虽然Smagorinsky型LES模型通常使用，我们采用了一个方程LES模型。由于亚网格湍流方程中的尾流产生项是不可忽略的。通过与实测数据的比较，验证了单方程大涡模拟模型的正确性。

In this study, we proposed two kinds of turbulence models for diffusion and absarption oficontamioant and carbon dioxide within vegetation. One (k-ε) type model and the other is a LES(Large Eddy Simulation) model. In cam of (k-ε) model, we adopt the procedure where we took the ensemble avenges and then the spatial averages of the basic equations. A filter was adopted for the spatial average. We assumed that tie filter was sufficiently smooth, though it was top-hat type. The drag force due to pressure and strain was analytically derived from taking the ensemble-averaged Navier-Stokes equation. Moreover, the equations of turbulent energy and viscous dissipation rate were derived from the basic equations. The effects of vegetation on the equations of turbulent energy and viscous dissipation rate were modeled and the equations were closed The validation was tried by comparing the results from the model with the measured data. In case of LES model, we adopted the sufficiently smooth top-bat filter. Although Smagorinsky-type LES models are usually used, we adopted a one-equation LES model. Because the wake production term which appears in the subgrid-scale turbulence equation is not negligible. The one-equation LES model was validated by comparing the result of the model with the measured data.