城市道路交叉口气流运动的三维数值模拟

Three-dimensional Numerical Simulation on Airflow at Urban Intersection

采用数值模拟的方法,探究了城市道路交叉口内的气流运动规律。基于德国汉堡大学风洞试验中的交叉口物理模型,采用耦合湍流模型的N-S方程,数值求解了交叉口处的三维气流场。数值模拟结果与风洞实验结果基本符合,达到了相互印证的效果。数值模拟结果表明:对于有纵向偏移(偏移量等于建筑物高度)的道路交叉口,在与来流风向垂直的纵向街道的水平面上形成三个旋涡;在远离交叉口中心并与来流风向垂直的交叉口街道峡谷内垂直面上形成一个顺时针旋涡;由于存在建筑物偏移,交叉口处的空气交换表现为来流从左方和上方街道导入,而从右方和下方街道导出,该空气交换特征与对称交叉口的空气交换规律截然不同。

A three-dimensional numerical investigation was conducted on airflow field in an urban street intersection.In the numerical method,the N-S equation coupled with the turbulence model was adopted.The geometries of the street intersection are exactly the same as those of the physical intersection model adopted in a wind tunnel experiment carried out at Hamburg University,Germany.The numerical results agree reasonably well with the wind tunnel experimental data.The numerical results indicate that in the street intersection with offset constructions,of which the offset amount equals to the height of the constructions,there would be three eddies on the horizontal plane of the intersection,which is vertical to the direction of the inlet airflow;in the street canyon which is away from the center of the intersection and vertical to the inlet airflow,there would be a clockwise eddy on the vertical plane;because of the existence of offset constructions,air exchange in the intersection manifests that airflow flows into the intersection from the left and upper streets and flows out from the right and underneath streets.Such kind of air exchange differs significantly from the airflow feature in symmetrical intersections.