热力效应作用下小区风环境风洞试验研究

温度作为影响城市舒适度的主要因素之一,对流场的作用机理到目前为止尚不明确。为揭示温度场对流场的影响规律,基于大尺寸风洞,对不同热力条件下的平均风进行试验研究,得出不同理查逊数R_b作用下的人行高度风速、相关测点顺风向速度和雷诺剪切应力分布并进行详细分析。以长沙市某小区为研究背景,探究了不同热力效应下人行高度风场的分布规律,获取了热力条件下典型测点的相关性系数,并利用超越概率的方法定量评估了热力效应下的小区人行高度风环境。结果表明:在-0.38<R_b<0范围内,空风洞流场随着热力效应增大,在近地面风速增长相对较大,且随着高度的增加其增幅逐渐减缓; 实际中小区人行高度风环境受温度影响整体较小,主要影响集中在风速比0.6以下,最大均方根为0.635,风速比在0.6以上时温度对风速影响效果相对较小; 热力效应对人行高度风场的相关性与舒适度影响较小,其最大影响值分别为8%和3.87%。

Study on wind tunnel test of urban wind environment under thermal effects

Temperature is one of the main factors affecting the comfort of the city, the mechanism of the flow field is not clear so far. In order to reveal the influence of temperature field on the flow field, based on the large-scale wind tunnel, the average wind under different thermal conditions was tested and studied. The wind speed at pedestrian height, the along-wind speed of relevant measuring points and the distribution of Reynolds shear stress under different Richardson numbers R_b were obtained and analyzed in detail. Taking a residential district in Changsha as the research background, the distribution law of wind field at pedestrian height under different thermal effects was explored, the correlation coefficient of typical measuring points under thermal conditions was obtained, and the wind environment at pedestrian height under thermal effects was quantitatively evaluated by the method of exceedance probability. The results show that in the range of -0.38<R_b<0, the flow field of the empty wind tunnel increases with the thermal effect, and the near-surface wind speed increases relatively large, and the increase gradually slows down with the increase of height. In practice, the wind environment of pedestrian height in the community is less affected by temperature as a whole. The main influence is concentrated below the wind speed ratio of 0.6, and the maximum root mean square is 0.635. When the wind speed ratio is above 0.6, the effect of temperature on wind speed is relatively small. The thermal effect has little influence on the correlation and comfort degree of pedestrian height wind field, and the maximum influence values are only 8% and 3.87%.