对流边界层中粒子随机扩散模式和高斯模式的比较

THE COMPARE BETWEEN THE MONTE-CARLO DIFFUSIVE MODEL AND THE GAUSS MODEL IN CONVECTIVE BOUNDARY LAYER

关键词:  对流边界层  粒子随机扩散模式  高斯模式  湍流

Key words:  Convective boundary layer  Gauss model  Monte-Carlo diffusion model  Turbulence

摘要:

用粒子随机扩散模式和高斯模式模拟的对应3种源高的横风向积分浓度的结果与水槽试验的结果进行比较,发现粒子随机扩散模式能较好地模拟出水槽试验结果,说明该模式能用来模拟对流边界展的扩散,而高斯模式不能完全反映对流边界层的扩散。比较两种模式的模拟结果,发现粒子随机扩散模式由于考虑了对流边界层中白卷流和热泡引起的垂直方向上湍流的非均一性,比高斯模式能较好地模拟出污染物在垂直方向上充分混合较快、水平方向上扩散范围大、地面浓度最大值大、浓度最大值出现位置距源近且向右手方(背风而立)偏移等特点,并由此说明了环境影响评价中应用高斯模式时应注意的问题。最后,用对流边界层中大气湍流结构特征对模拟结果作了解释。

Abstract:

The simulative results of crosswind integrated concentration at three source heights from Monte-Carlo diffusive model and Gauss model are compared with the result of convective tank. It is found that the Monte-Carlo diffusive model can well simulate the result of convective tank and Gauss model can’t completely simulate that. It demonstrates that the diffusion in convective boundary layer can be simulated using the Monte-Carlo diffusive model. By comparing the results simulated with these two kinds of models in vertical and horizontal directions, we found that the characteristics of quick mixture in vertical direction and diffusive range, the maximum of ground concentration, the position of the maximum and the displace towards right hand in horizontal can be simulated by the Monte-Carlo diffusive model because the non-uniformity of turbulence in vertical direction is considered, which is caused by the plumes and thermals in convective boundary layer. The problems using the Gauss model in environmental compact assessment is demonstrated. The simulative results above are explained using the structure characteristics of the atmospheric turbulence in convective boundary layer.