基于PIV试验的积雪平屋面风场特性研究

郑云; 刘志祥; 余志祥; 傅彦青

doi:10.3969/j.issn.0258-2724.20210262

基于PIV试验的积雪平屋面风场特性研究

doi: 10.3969/j.issn.0258-2724.20210262

1.
中冶建筑研究总院有限公司，北京 100191
2.
西南交通大学土木工程学院，四川成都 610031

基金项目: 国家钢结构工程技术研究中心开放基金（YZB2019Ky03）；中国国家铁路集团有限公司科技研究开发计划（N2020T004）；国家重点研发计划（2016YFC0802205-1）；国家自然科学基金（51378428）

详细信息

作者简介:
郑云（1976—），男，教授级高工，研究方向为钢结构、结构诊治，E-mail：nrcsc@139.com

通讯作者:
余志祥（1976—），男，教授，博导，研究方向为结构风雪荷载，防护结构，E-mail：yzxzrq@home.swjtu.edu.cn

中图分类号: TU208.2；TU312
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- 被引次数: 0
出版历程
- 收稿日期: 2021-04-07
- 修回日期: 2021-06-21
- 网络出版日期: 2022-11-09
- 刊出日期: 2021-07-06

Wind Field Characteristics of Snow-Covered Low-Rise Building Roof Based on PIV Experiments

1.
Central Research Institute of Building and Construction Co., Ltd., MCC Group, Beijing 100191, China
2.
School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China

摘要

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.
- 低矮建筑 /
- PIV试验 /
- 屋盖积雪 /
- 流动特性 /
- 大涡模拟
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.
- low-rise building /
- PIV experiment /
- snowdrift on roof /
- flow characteristic /
- large-eddy simulation.

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图 1 典型模型概况

Figure 1. Sketch view of typical model

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图 2 来流风速和湍流度剖面

Figure 2. Wind velocity and turbulent intensity of oncoming flow

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图 3 PIV风洞试验

Figure 3. PIV experiments in wind tunnel

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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

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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

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图 6 模型 1～4屋面时均流线分布

Figure 6. Time-averaged streamlines for models 1–4

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图 7 模型 1～4屋面上方涡量场分布

Figure 7. Distributions of time-averaged vortices for models 1–4

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图 8 各工况下有/无积雪屋面涡量值对比

Figure 8. Comparison of vortices for all cases

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图 9 计算域及网格

Figure 9. Computational domain and mesh

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图 10 LES与PIV速度对比

Figure 10. Comparison of velocity between PIV and LES

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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

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图 12 模型中轴线风压系数分布

Figure 12. Wind pressure coefficient along the model axis

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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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表 3 涡核和再附长度对比

Table 3. Vortex position and reattachment length

方法	有无积雪	x_s/H	z_s/H	L_s/H
本文 PIV	有/无	0.58	0.19	1.35
本文 LES	有/无	0.64	0.18	1.38
本文 LES	有/无	0.41	0.10	0.75
Kim等 ^[14] PIV	无	0.60	0.19	1.01
孙虎跃等^[20] PIV	无	0.70	0.19	1.52
注：x_s为涡核到分离点距离；z_s为涡核到屋面高度；L_s为分离涡再附点到分离点距离.

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