城市重气扩散模型SLAB_URBAN外场试验模拟验证

Field test simulation verification of an SLAB_URBAN dispersion model Of the denser-than-air gas

研究适用于模拟城市中危险化学品扩散的重气扩散模型SLAB_URBAN。模型中考虑了城市冠层内风的特征,即引入基于城市形态学的风速廓线计算方法。分别采用SLAB_URBAN模型和SLAB模型对2000年盐湖城的重气扩散试验进行模拟,主要验证下风方向不同观测距离的气体最大小时平均浓度与源释放速率的比值。结果表明,SLAB_URBAN模型的模拟结果比SLAB模型更接近观测值。从应急反应和安全角度上来说,SLAB_URBAN模型也符合实际工作的需求。

The present paper is engaged in the study of a Salt Lake City Urban （SLC） 2000 （URBAN 2000） tracer data sets, which is adopted to demonstrate the SLAB _ URBAN and SLAB model perfor- mance. As is known, large quantities of toxic chemicals can be a- massed up at some industrial factories and then carried over by the moving trains or trucks from area to area. For higher molecular weight and lower temperatures, many chemicals arc released into the air as the denser-than-air gases. If the release were to occur in a densely- populated environment, the buildings and other obstacles will signifi- cantly affect the spreading. To simulate such unusual atmospheric dispersion of denser-than-air gases, we have developed an urban denser-than-air dispersion model known as SLAB _ URBAN model for simulating the releases of such gas over the cities and their surround- ing areas with thick industrial facilities. The model we have devel- oped is based on the shallow layer theory, which helps to calculate such hazardous chemicals dispersion by solving the equations of mass conservation, momentum conservation, energy and species. The model can help to work out the mean wind profile above and under the urban canopy for nearly neutral stabilities in urban area. The tracer SF6 was released during the night near street level in the down- town area with its concentrations observed at three sampling arcs. The focus of the comparisons is on the maximum concentration Cm~, on a given monitoring arc, normalized by thc emission rate Q. The statis- tical tests show the evaluation results gained by using SLAB_ URBAN model proves much more in agreement with the observation data than with SLAB models＇ . In addition, the SLAB _ URBAN model could be used for emergency response and can meet the needs of the practical work.