顶部方形开洞对超高层建筑风荷载影响的大涡模拟研究

Large eddy simulation for effects of square opening at top on wind load of super tall building

顶部开洞是一种有效的超高层建筑气动优化措施,开洞形式和洞口位置对建筑整体风荷载的影响机理还有待进一步研究。采用基于空间平均的大涡模拟方法,考虑来流与洞口方向一致,研究了顶部无开洞(标准方柱)、敞开式和封闭式方形开洞,对湍流边界层风场内方形截面超高层建筑风荷载的影响。将封闭式方形开洞模型风压系数的大涡模拟与风洞试验结果对比,验证了该数值模拟方法及参数设置的正确性;对比分析了上述无、有顶部开洞及开洞形式的方柱表面平均和脉动风压分布特征,着重从流场角度分析了洞口形式对风荷载的影响机理。结果表明:顶部开洞影响了流动分离点位置、剪切流扩散角度及流动再附现象,洞口的狭管效应使得该处风速急剧增大,其中封闭式开洞更为显著,洞口内加速的气流扰乱了大尺度的涡流,导致涡的能量更加分散,从而减弱了结构表面风压;在顶部洞口边缘处,因流动分离而出现了较大风压值,其中敞开式洞口的背风面存在较为明显的边缘效应;封闭式开洞对减弱洞口局部风压的效果优于敞开式。

Opening at top is an effective aerodynamic optimization measure for super tall building,and the impact mechanism of opening form and opening position on overall wind load of building still needs further study.Here,using the large eddy simulation method based on space average,considering incoming flow direction is consistent with that of opening,effects of no opening at top(standard square column),open-type and closed-type square openings on wind load of square section super tall building in turbulent boundary layer wind field were studied.Firstly,large eddy simulation results for wind pressure coefficient of closed-type square opening model was compared with wind tunnel test results to verify the correctness of the numerical simulation method and parametric settings proposed here.Then,average and fluctuating wind pressure distributions’characteristics on surface of square columns with and without top openings were analyzed contrastively,the influence mechanism of opening forms on wind load was analyzed emphatically from the perspective of flow field.The results showed that opening at top affects position of flow separation point,angle of shear flow diffusion and phenomenon of flow reattachment;the narrow tube effect of opening causes a sharp increase in wind speed at the opening position,especially,for closed-type opening,this phenomenon is more significant;accelerated airflow inside opening disrupts large-scale eddies to cause energy of eddies being more dispersed and structure surface wind pressure being weaker;at edge of top opening,a larger wind pressure value appears due to flow separation,an obvious edge effect exists on leeward side of open-type opening;the weakening effect of closed-type opening on opening local wind pressure is better than that of open-type opening.