场区尺度风场和污染物扩散快速预测系统构建及应用

Construction and application of a field-scale rapid prediction system for wind field and pollutant dispersion

目的构建快速预测系统,提高场区尺度核事故后果评价计算精度和效率。方法开展场区尺度范围内复杂下垫面周围风场和污染物扩散的快速预测方法研究,采用风场诊断模型和拉格朗日粒子扩散方法,以显式分辨建筑物和植被分布的方式,建立场区尺度快速预测系统;通过数值模拟理想和真实城市场区算例,并与风洞实验测量数据和计算流体力学数值结果进行比较,研究复杂下垫面对局地风场和污染物输运的影响。结果快速预测系统能在约5 min时间内清晰的模拟出局地高分辨率风场以及污染物浓度分布信息,建立与地理信息软件的接口,并可以实现与中尺度气象预报模式的耦合;从计算准确性上看,系统对风场模拟效果良好,风速和风向的分数偏差分别为0.33和-0.08,模拟的浓度场的范围受风场影响较大,除个别低浓度点外,模拟和观测的浓度比值在0.05~3.40之间。结论快速预测系统可以在保证计算精度的基础上,有效模拟出流场分布特征,提高计算效率,为核事故应急响应提供重要参考和依据。

Objective To construct a rapid prediction system to improve the accuracy and efficiency of evaluation of the consequences of nuclear accidents at a field scale.Methods Base on a diagnostic wind field model and Lagrangian particle diffusion,we established a rapid prediction method for wind field and pollutant dispersion around complex underlying surfaces within a field scale,in a way of visual discrimination of buildings and vegetation distribution.With data simulation and the use of a real urban field example,the simulated results were compared with wind tunnel test measurements and computational fluid dynamics results to study the influence of complex underlying surfaces on wind field and pollutant transport in the region.Results The rapid prediction system could clearly simulate the high-resolution wind field and pollutant concentration distribution of the region in about five minutes.It could interface with geographic information software and couple with a mesoscale weather prediction model.In terms of accuracy,the system performed well in wind field simulation,with the fractional deviations of wind speed and wind direction being 0.33 and−0.08,respectively.Concentration field simulation was greatly affected by the wind field,and the ratios of simulated concentrations to observed concentrations were between 0.05 and 3.4,except for a few low concentration points.Conclusion The rapid prediction system can effectively simulate the distribution characteristics of the flow field and improve calculation efficiency when ensuring calculation accuracy,which provides an important reference for emergency response to nuclear accidents.