基于大涡模拟的大气边界层湍流强度对低矮房屋风荷载特性影响研究

对德州理工大学(Texas tech university，TTU)低矮房屋标准模型，以已有现场实测以及缩尺模型风洞实验数据为验证对比，基于大涡模拟(Large-eddy simulation，LES)方法研究了大气边界层湍流强度对低矮房屋风荷载特征的影响机理。采用CDRFG (Consistent discretizing random flow generation) 人工合成湍流方法生成大气边界层湍流，研究了来流湍流度对低矮建筑表面的平均、脉动以及极小值风压分布以及风压非高斯特性的影响，并利用LES能提供非常场流动全流域信息的优势，结合瞬态湍流场结构对大气边界层湍流对低矮房屋风荷载特征的影响机理进行了阐释。结果表明:LES数值模拟得到的平均、脉动及极小值风压系数与实验以及实测结果一致，平均风压结果包络在实测误差范围以内，极小值风压系数最大误差小于10%，脉动风压系数最大误差小于20%且误差区域较小。在来流湍流度增大的过程中，低矮房屋屋面平均风压系数变化较小，脉动风压系数呈显著的线性增加；极小值风压系数变化规律相对复杂，呈现出非线性减小的趋势，风压系数极小值可达?5.0；屋面涡脱强度逐渐被抑制，锥形涡迹线与屋面迎风前缘的夹角由14.4°下降至8.7°。屋面风压非高斯特性主要与屋面形成的涡旋结构相关，表现出典型的右偏软化非高斯过程，且随着来流湍流度的增加风压非高斯特性逐渐减弱。从流场的角度来看，湍流度的增加抑制屋面迎风前缘柱状涡以及锥形涡的形成，加快流动分离的再附，减少分离泡尺度，同时提高了屋盖周围的湍流高频能量成分，从而使脉动风压增加，极小值风压减小以及风压非高斯特性减弱。该研究阐明了大气边界层湍流对低矮房屋风荷载特性的影响机理，有助于进一步理解低矮房屋风致破坏机理，并且为低矮房屋的抗风设计及抗风性能优化提供重要参考。

EFFECTS OF UPSTREAM TURBULENCE INTENSITY ON AERODYNAMIC LOADS OF LOW-RISE BUILDINGS IN ATMOSPHERIC BOUNDARY LAYER FLOW USING LARGE EDDY SIMULATION

Based on the existing benchmark for low-rise buildings by TTU (Texas tech university), this study numerically investigates the effects of upstream turbulence intensity on the aerodynamic loadings on a low-rise building in the atmospheric boundary layer flow using Large-eddy simulation (LES). The consistent discretizing random flow generation (CDRFG) method was adopted to reproduce the boundary layer turbulence. The effects of upstream turbulence intensity on the wind effects of the low-rise building were investigated in the context of statistical characteristics of wind pressures and flow visualizations. The results show that the LES results agreed well with the wind tunnel tests and on-site measurements, and the variation of peak pressure coefficients between LES and wind tunnel tests is less than 10%, and the variation of fluctuating pressure coefficients is less than 20%. And the increase of turbulence intensity enhanced the fluctuating aerodynamic loadings and negative peak pressure coefficients and reduced the flow reattachment length, while the mean wind pressure coefficients were trivially affected. The extreme value of the negative peak pressure coefficients is around ?5, and with the increase of turbulence intensity, the angle between the vortex central line and the edge of roof is reduced from 14.4° to 8.7°. Moreover, the upstream turbulence intensity has significant effects on the non-Gaussian characteristics of wind pressure on the roofs, especially in the separation region. In terms of flow visualizations, the increase of turbulence intensity would mitigate the flow separation and vortex shedding on the roof, and the vortical structures around the roof became more complex and the quantity of small-scale eddies increased, thereby resulting in an increase of wind pressure fluctuations and a decrease of negative peak pressure coefficients and non-Gaussianity. The outcomes of this study revealed the effects and underlying mechanism of upstream turbulence intensity for the aerodynamic loadings on the low-rise building roof, which would facilitate our understanding for the wind-induced disasters of the low-rise building and provide a useful reference for the wind-resistant design and for aerodynamic performance optimization of the low-rise building.