WRF-Fluent耦合模式的构建及其对城市大气扩散的精细化模拟

为了准确刻画城市环境中的复杂建筑结构对大气运动和污染物输送及扩散过程的影响，结合中尺度模式WRF和微尺度模式Fluent构建了单向耦合的WRF-Fluent模式，并将其应用于榆中县城区高架源排放情景下大气扩散的模拟研究.基于城市气象/示踪外场试验期间获取的气象数据对WRF模式的模拟性能进行验证，发现WRF能够为Fluent提供比较准确的随时间变化的气象驱动场.在此基础上，将榆中县城区三维几何模型嵌入到WRF-Fluent中，对城区内的流场及污染烟羽的时空演变过程进行精细化模拟，并将模拟结果与实测示踪物浓度数据进行比对.结果显示，WRF-Fluent模式可以很好地描述城区内的复杂三维风场结构以及污染烟羽随时间的动态变化特征，而且模拟的地面和城市冠层顶浓度最大值基本位于观测值的0.3~3倍之内，这表明构建的WRF-Fluent模式具有较好的模拟性能，可作为一种有效的工具应用于实际城市规划和空气质量改善以及环境风险评估等方面的研究.

Elaborated simulation of urban atmospheric dispersion using an established WRF-Fluent coupling model

To accurately characterize the effect of complex urban building structures on pollutant transport and diffusion processes, a one-way coupled WRF-Fluent model was constructed and applied to simulate the pollutant dispersion from an elevated source in Yuzhong county. The performance of WRF model was validated systematically using data obtained from the Urban Meteorological and Tracer Experiment, and it is found that WRF can provide accurate and time-varying meteorological driving field for Fluent. The spatial and temporal evolution of the flow field and pollution plume in Yuzhong County was simulated explicitly using WRF-Fluent model with embedded three-dimensional geometric model of Yuzhong County and the results were compared to the measured tracer concentration data. The WRF-Fluent model can well reproduce the complex flow patterns and the evolution of the polluted plume. The simulated maximum ground level and urban canopy top concentrations are within a factor of three of the observations. The constructed WRF-Fluent model has good performance for urban dispersion, and is an effective tool for urban planning, urban air quality management and environmental risk assessment.