Wind Field Characteristics of Snow-Covered Low-Rise Building Roof Based on PIV Experiments
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摘要:
为研究屋盖积雪对低矮平屋面风场特性的干扰影响，基于风吹雪风洞试验，通过3D打印获得平屋面的3D积雪形态，并以无积雪模型作为对照，系统地开展了PIV （particle image velocimetry）风洞试验，并结合LES （large eddy simulation）方法，研究了6组平屋面建筑有无积雪时的流场分布特性. 试验研究表明：当无积雪时，来流在屋面前缘处分离后能形成典型的分离泡流动，分离泡内速度场存在明显逆流现象；当有积雪时，屋面上方的逆流减弱甚至消失，积雪显著地加快了流经屋面附近流场的速度，其最大速度增量约为0.6，同时，流线分布更贴合模型壁面，速度梯度增大，也相对增大了涡量值；积雪会使得屋面上方整体的时均湍动能和切应力均减小，但对屋面迎风区域的平均和脉动风压均有增大作用，其增大比值约为15%和20%. 通过该研究可进一步对低矮建筑的风雪荷载作用机理展开分析，为屋盖结构的抗风雪设计提供参考.
Abstract:To investigate the influence of snowdrifts on the flow field above low-rise building roof, the distributions of flow field above six different low-rise building roofs with or without snowdrifts were systematically analyzed through particle image velocimetry (PIV) experiments in wind tunnel combined with large eddy simulation (LES), where the tested models with snowdrifts were obtained by 3D printing based on the results of blowing snow experiments. The results indicate that a typical separation bubble can be formed above the no-snow roof when the approaching flow is separated at the leading edge, in which the obvious inverse flow can be observed. However, when there are snowdrifts on the roof, the backflow near the roof is weakened or even disappeared, which remarkably accelerates the flow velocity near the roof, and the maximum speed increment is about 0.6. Concurrently, the distributions of streamlines for snowdrift cases are closer to the building surface and have a larger velocity gradient, and hence the vorticity is also increased. The further numerical research on the turbulent characteristic above the building roof based on LES indicates that the turbulent kinetic energy and turbulence shear stresses above the snowdrift roof are also significantly smaller than their counterparts above the no-snow roof. However, the snowdrift increases the mean and fluctuating wind pressures in the windward region of the roof, and the reduction ratio is about 15% and 20%, respectively. Through this study, the mechanism of wind and snow load on low-rise buildings can be further analyzed, which can provide a reference for the wind-and-snow resistant design of roof structures.
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Key words:
- low-rise building /
- PIV experiment /
- snowdrift on roof /
- flow characteristic /
- large-eddy simulation.
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图 4 模型 2有/无积雪情况的时均速度分布
Figure 4. Distributions of the mean streamwise and vertical velocities for model 2 with and without snowdrifts
图 5 有/无积雪时屋面特定路径上的速度对比
Figure 5. Comparison of streamwise velocities atthe specific route for all cases
图 11 有无积雪时湍动能和湍流应力分布对比
Figure 11. Comparison in distributions of turbulent kinetic energy (k) and turbulent shear stresses (
${u}_1{w}_1$ )with and without snowdrifts表 1 PIV试验工况
Table 1. PIV experiment cases
模型编号 L/H W/H 有无积雪 模型 1 1.0 2.0 有/无 模型 2 2.0 2.0 有/无 模型 3 3.0 2.0 有/无 模型 4 4.0 2.0 有/无 模型 5 2.0 1.0 有/无 模型 6 2.0 3.0 有/无 
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表 2 边界条件和求解设置
Table 2. Boundary conditions and solution settings
计算条件 边界条件及求解设置 入口 速度入口，式（1） 出口 压力出口 两侧和顶部 对称边界 建筑和地表 无剪切壁面 求解算法 分裂算子的压力-隐式方法 动量项离散 有界中心差分 时间步长/s 0.000 2 总物理时间/s 10
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[1] TSUCHIYA M, TOMABECHI T, HONGO T, et al. Wind effects on snowdrift on stepped flat roofs[J]. Journal of Wind Engineering and Industrial Aerodynamics, 2002, 90(12/13/14/15): 1881-1892. [2] 赵雷,余志祥,齐欣,等. 低矮建筑屋盖风雪流作用场地实测与数值模拟[J]. 振动与冲击,2017,36(22): 225-231,244. doi: 10.13465/j.cnki.jvs.2017.22.035ZHAO Lei, YU Zhixiang, QI Xin, et al. Field measurements and numerical simulation of snowdrift on low-rise buildings[J]. Journal of Vibration and Shock, 2017, 36(22): 225-231,244. doi: 10.13465/j.cnki.jvs.2017.22.035 [3] ZHOU X Y, KANG L Y, YUAN X M, et al. Wind tunnel test of snow redistribution on flat roofs[J]. Cold Regions Science and Technology, 2016, 127: 49-56. doi: 10.1016/j.coldregions.2016.04.006 [4] LIU Z X, YU Z X, ZHU F, et al. An investigation of snow drifting on flat roofs: Wind tunnel tests and numerical simulations[J]. Cold Regions Science and Technology, 2019, 162: 74-87. doi: 10.1016/j.coldregions.2019.03.016 [5] YU Z X, ZHU F, CAO R Z, et al. Wind tunnel tests and CFD simulations for snow redistribution on 3D stepped flat roofs[J]. Wind and Structures, 2019, 28(1): 31-47. [6] 余志祥,赵雷,赵世春,等. 基于CFD-DEM耦合的屋面积雪分布数值模拟[J]. 建筑结构学报,2017,38(10): 116-122.YU Zhixiang, ZHAO Lei, ZHAO Shichun, et al. Simulation of snow distribution on typical roofs using coupled CFD and DEM methods[J]. Journal of Building Structures, 2017, 38(10): 116-122. [7] ZHOU X Y, KANG L Y, GU M, et al. Numerical simulation and wind tunnel test for redistribution of snow on a flat roof[J]. Journal of Wind Engineering and Industrial Aerodynamics, 2016, 153: 92-105. doi: 10.1016/j.jweia.2016.03.008 [8] ZHAO L, YU Z X, ZHU F, et al. CFD-DEM modeling of snowdrifts on stepped flat roofs[J]. Wind and Structures, 2016, 23(6): 523-542. [9] CASTRO I P, ROBINS A G. The flow around a surface-mounted cube in uniform and turbulent streams[J]. Journal of Fluid Mechanics, 1977, 79(2): 307-335. doi: 10.1017/S0022112077000172 [10] BLOCKEN B, STATHOPOULOS T, VAN BEECK J P A J. Pedestrian-level wind conditions around buildings: Review of wind-tunnel and CFD techniques and their accuracy for wind comfort assessment[J]. Building and Environment, 2016, 100: 50-81. doi: 10.1016/j.buildenv.2016.02.004 [11] CASTRO I P, DIANAT M. Surface flow patterns on rectangular bodies in thick boundary layers[J]. Journal of Wind Engineering and Industrial Aerodynamics, 1983, 11(1/2/3): 107-119. [12] ZHAO Z. Wind flow characteristics and their effects on low-rise buildings[D]. Lubbock: Texas Tech University, 1997. [13] KIYA M, SASAKI K. Structure of large-scale vortices and unsteady reverse flow in the reattaching zone of a turbulent separation bubble[J]. Journal of Fluid Mechanics, 1985, 154: 463-491. doi: 10.1017/S0022112085001628 [14] KIM K C, JI H S, SEONG S H. Flow structure around a 3-D rectangular prism in a turbulent boundary layer[J]. Journal of Wind Engineering and Industrial Aerodynamics, 2003, 91(5): 653-669. doi: 10.1016/S0167-6105(02)00459-2 [15] AKON A F, KOPP G A. Turbulence structure and similarity in the separated flow above a low building in the atmospheric boundary layer[J]. Journal of Wind Engineering and Industrial Aerodynamics, 2018, 182: 87-100. doi: 10.1016/j.jweia.2018.09.016 [16] 董欣,叶继红. 大跨屋盖表面旋涡的PIV试验研究[J]. 工程力学,2014,31(11): 161-169. doi: 10.6052/j.issn.1000-4750.2013.05.0486DONG Xin, YE Jihong. PIV experimental investigation of vortices on large-span roofs[J]. Engineering Mechanics, 2014, 31(11): 161-169. doi: 10.6052/j.issn.1000-4750.2013.05.0486 [17] MAJOWIECKI M. Snow and wind experimental analysis in the design of long-span sub-horizontal structures[J]. Journal of Wind Engineering and Industrial Aerodynamics, 1998, 74/75/76: 795-807. [18] HOLICKY M, SYKORA M. Failures of roofs under snow load: Causes and reliability analysis [M]. Washington D. C.: Pathology of the Built Environment, 2010: 444-453. [19] COUNIHAN J. An improved method of simulating an atmospheric boundary layer in a wind tunnel[J]. Atmospheric Environment, 1969, 3(2): 197-214. doi: 10.1016/0004-6981(69)90008-0 [20] 孙虎跃,叶继红. 基于PIV技术的平屋盖表面分离泡流动结构研究[J]. 工程力学,2016,33(11): 121-131.SUN Huyue, YE Jihong. 3D characteristics of separation bubbles around flat roofs by PIV technique[J]. Engineering Mechanics, 2016, 33(11): 121-131. -
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