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首页> 外文期刊>Journal of hydrometeorology >The Collection Efficiency of Shielded and Unshielded Precipitation Gauges. Part I: CFD Airflow Modeling
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The Collection Efficiency of Shielded and Unshielded Precipitation Gauges. Part I: CFD Airflow Modeling

机译：屏蔽式和非屏蔽式雨量计的收集效率。第一部分：CFD气流建模

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The aerodynamic response of snow gauges when exposed to the wind is responsible for a significant reduction of their collection performance. The modifications induced by the gauge and the windshield onto the space-time patterns of the undisturbed airflow deviate the snowflake trajectories. In Part I, the disturbed air velocity field in the vicinity of shielded and unshielded gauge configurations is investigated. In Part II, the airflow is the basis for a particle tracking model of snowflake trajectories to estimate the collection efficiency. A Geonor T-200B gauge inside a single Alter shield is simulated for wind speeds varying from 1 to 8 m s(-1). Both time-averaged and time-dependent computational fluid dynamics simulations are performed, based on Reynolds-averaged Navier-Stokes (RANS) and large-eddy simulation (LES) models, respectively. A shear stress tensor k- model (where k is the turbulent kinetic energy and is the turbulent specific dissipation rate) is used for the RANS formulation and solved within a finite-volume method. The LES is implemented with a Smagorinsky subgrid-scale method that models the subgrid stresses as a gradient-diffusion process. The RANS simulations confirm the attenuation of the airflow velocity above the gauge when using a single Alter shield, but the generated turbulence above the orifice rim is underestimated. The intensity and spatial extension of the LES-resolved turbulent region show a dependency on the wind speed that was not detected by the RANS. The time-dependent analysis showed the propagation of turbulent structures and the impact on the turbulent kinetic energy above the gauge collecting section.
机译：当雪量计暴露在风中时，其空气动力响应会大大降低其收集性能。仪表和挡风玻璃对未扰动气流的时空模式引起的变化使雪花轨迹偏离。在第一部分中，研究了屏蔽和非屏蔽仪表配置附近的扰动空气速度场。在第二部分中，气流是雪花轨迹的粒子跟踪模型估算收集效率的基础。模拟了单个Alter防护罩内的Geonor T-200B仪表，其风速从1到8 m s（-1）不等。分别基于雷诺平均Navier-Stokes（RANS）模型和大涡模拟（LES）模型，进行了时间平均和时间相关的计算流体动力学模拟。剪应力张量k模型（其中k是湍动能，是湍流比耗散率）用于RANS公式，并在有限体积法内求解。 LES是通过Smagorinsky子网格规模方法实现的，该方法将子网格应力建模为梯度扩散过程。 RANS仿真证实了使用单个Alter防护罩时仪表上方气流速度的衰减，但是在孔口边缘上方产生的湍流被低估了。 LES分辨的湍流区域的强度和空间扩展显示出对风速的依赖，而RANS并未检测到。随时间变化的分析表明，湍流结构的传播以及对液位计收集区上方湍动能的影响。

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