基于大涡模拟的平屋盖锥形涡数值分析研究

Large Eddy Simulation of the Characteristics of Conical Vortex on a Flat Roof

采用大涡模拟(LES)对平屋盖建筑受45°风向角作用下的表面风荷载问题进行了非稳态数值模拟分析.通过与风洞试验结果的对比得出,大涡模拟能较好地捕捉到建筑物顶面出现的锥形涡及其特性.在此基础上,研究了锥形涡作用下建筑物顶面平均风压与脉动风压的分布,以及加设分隔挡板和不同高度的女儿墙对屋面风压分布和旋涡强度的影响.研究结果表明,基于Q准则的旋涡判别法可以较好地识别斜风向下屋面形成的锥形旋涡;在背风区锥形涡与侧面脱体涡相互作用并脱落,其影响将反馈至屋面旋涡上导致屋盖两个锥形涡强度以屋面对角线为轴交替波动,此消彼长;屋面女儿墙的存在使得两个锥形涡之间的间隙变窄,旋涡足迹变阔,且屋面峰值吸力随女儿墙高度的增加而迅速减小.

This paper was concerned with the unsteady characteristics of the conical vortex on a flat roof on the basis of numerical results by large eddy simulation （LES） when an approaching flow attacks at about 45 degrees against the wall. The results indicate that the large eddy simulation （LES） can give fairly good results, compared with the experiment pressure data of the AIJ flat roof model and other wind tunnel tests. Based on the Q criterion, this paper presented the flow visualization of conical vortices on the roof. By analyzing the mean and fluctuating pressure coefficients on the roof, it is observed that the strong suc- tion acts on near leading edge on the flat roof of the building. The strong suction is caused by a pair of con- ical vortices whose strength is unbalanced in any time. When the strength of one vortex recedes, the vor- tex on the other side is strengthened. By adding splitter plates and parapets, the LES results show that the switching of conical vortices may have inseparable relations with the interaction of vortices formed in the wake shed from the sidewalls of the building. Additionally, the parapets can mitigate the high corner suctions on the roof and lift the position of vortex core, while the dimension of the conical vortex is greater with the higher parapets.