风沙区高速公路波形梁护栏附属设施影响下的气流变化及蚀积特征

Air flow variation and erosion characteristics under the influence of the W-beam guardrail of the expressway in aeolian sand area

为揭示风沙地区高速公路波形梁护栏对气流的影响,探究护栏影响下的高速公路路面积沙原因,文中采用Realizable k-ε方程结合增强壁面函数模型对路面波形梁护栏作用下的气流流场进行模拟,分析波形梁护栏影响下的三维气流场。结果表明:气流通过波形梁护栏时,在护栏底部和顶部受压加速,护栏正后方受到加速气流的分离填补,在护栏后侧形成对称涡,近地表气流向y+方向扩散形成上升流,地表剪切力增大,涡耗散消失后,地表气流动能最小。随着来流气流速度增加,护栏后方的涡呈现作用范围增大且涡周期脱落趋势。对照波形梁护栏影响下的气流特征和野外护栏影响下的积沙堆积部位有很好的映证关系,即风速在6-7m/s时,积沙部位在护栏后方2.5H处,即涡流耗散的边界。针对于三维风速和湍流难以直观测量的困难,该模拟计算为认识下空上密型构造物对流体的影响提供了方法和思路。

In order to reveal the air flow changes affected by the W-beam guardrails in aeolian flow process,and explore the reasons of the sand deposition on the pavement under the influence of the guardrails,the Realizablek-εequation combined with enhanced wall function model under the action of the W-beam guardrail is applied to simulate the flow field and analyze air flow state and velocity under the action of the different wind velocity.The results show that when the air flow passes through the W-beam guardrails,it is accelerated under pressure at the bottom and top of the guardrail.The airflow is separated and filled by the accelerating air flow directly behind the guardrail,and symmetric vortices are formed at the rear of the guardrail.The near surface air diffuses to the y+direction to form upwelling flow.With the increase of incoming air velocity,the vortex behind the guardrail shows an increasing range of action and a trend of vortex period shedding.There is a good correlation between the airflow characteristics under the influence of the control wave guardrail and the sand accumulation position under the influence of the field guardrail,that is,when the wind speed is 6-7m/s,the sand accumulation position is 2.5H behind the guardrail,that is the boundary of eddy current dissipation.Since it is difficult to measure the three-dimensional wind speed and turbulence directly,the simulation calculation provides a method and idea for understanding the influence of the dense structure on the fluid.