稳定层结下对称型街区污染物扩散的风洞研究

Wind Tunnel Study of Diffusion Around Symmetrical Street Canyon under Stable Stratification

通过风洞实验研究了来流与对称型街区迎风侧呈90°时,城市环境中不同温度层结(中性:Re_(δ)=2.15×10^(4),Ri_(δ)=0;稳定:Re_(δ)=2.0×10^(4),Ri_(δ)=0.76)对烟囱排放污染物扩散的影响。以对称型街区为研究对象,示踪气体(CO)从街区上风向的烟囱中释放,在下风向对街区尾流区域的平均风速、湍流强度以及浓度进行测量分析。结果表明:当大气层结稳定时,对称型街区近尾流区域的速度以及湍流强度小于中性层结。污染物在垂直方向上出现了下洗现象,在近尾流区,稳定条件下浓度增加。

The effect of atmospheric thermal stability(neutral:Re_(δ)=2.15×10^(4),Riδ=0;stable:Re_(δ)=2.0×10^(4),Riδ=0.76)on flow and dispersion of stack emissions in an urban environment is investigated using stratified wind tunnel experiments.Taking a symmetrical block as the research object,the tracer gas(CO)is released from the stack in the upwind direction of the block.The velocity,turbulence intensity and concentration are measured and analyzed in the downwind direction.The results show that when the atmospheric stratification is stable,the velocity and turbulence intensity around the symmetric block are smaller than those of the neutral stratification.The pollutants appear to wash down in the vertical direction.In the near wake region,the concentration increases under stable conditions.