The ventilation efficiency of three periodic building patterns of equal total volume and packing density is investigated: street canyons bounded by H uniform and 0.5H/1.5H variable height buildings, via wind tunnel measurements and Large Eddy Simulation. The numerical model utilizes the Transient Wind Forcing method to take the effect of eddies larger than the domain size into account, and a special Lagrangian dispersion model, which allows for the calculation of particle trajectories exceeding the periodic boundaries of the LES domain. The spatial and temporal characteristics of the concentration responses of both pulse-like and steady point sources located at the street surfaces are analyzed. It is shown that the variable building height has a favorable effect on urban ventilation in densely built areas: the average near-ground concentration can be reduced by up to 70% for the variable height buildings in a staggered arrangement. In terms of velocity, turbulence and concentration distributions, the model results are consistent with the experiments, verifying the applicability of the model for comparative air quality studies. Since the presented dispersion model is capable of handling dynamic changes in wind direction and magnitude, the accuracy of the TWF model can potentially overcome the limitations of wind tunnel tests.

研究了三种总容积和堆积密度相等的周期性建筑模式的通风效率：以H均匀和0.5 H /1.5 H为边界的街道峡谷通过风洞测量和大型涡流模拟获得高度可变的建筑物。数值模型利用瞬态风强迫方法来考虑大于区域大小的涡流的影响，并使用特殊的拉格朗日色散模型，该模型可以计算超过LES域周期边界的粒子轨迹。分析了位于街道表面的脉冲状和稳态点源的浓度响应的时空特征。结果表明，可变建筑高度对密集建筑区域的城市通风具有良好的影响：对于交错布置的可变高度建筑，平均近地浓度可降低多达70％。在速度，湍流和浓度分布方面，模型结果与实验一致，验证了该模型在比较空气质量研究中的适用性。由于提出的弥散模型能够处理风向和风量的动态变化，因此TWF模型的准确性可以克服风洞测试的局限性。