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首页> 外文期刊>Journal of hydrometeorology >The Collection Efficiency of Shielded and Unshielded Precipitation Gauges. Part II: Modeling Particle Trajectories
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The Collection Efficiency of Shielded and Unshielded Precipitation Gauges. Part II: Modeling Particle Trajectories

机译：屏蔽式和非屏蔽式雨量计的收集效率。第二部分：粒子轨迹建模

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The use of windshields to reduce the impact of wind on snow measurements is common. This paper investigates the catching performance of shielded and unshielded gauges using numerical simulations. In Part II, the role of the windshield and gauge aerodynamics, as well as the varying flow field due to the turbulence generated by the shield-gauge configuration, in reducing the catch efficiency is investigated. This builds on the computational fluid dynamics results obtained in Part I, where the airflow patterns in the proximity of an unshielded and single Alter shielded Geonor T-200B gauge are obtained using both time-independent [Reynolds-averaged Navier-Stokes (RANS)] and time-dependent [large-eddy simulation (LES)] approaches. A Lagrangian trajectory model is used to track different types of snowflakes (wet and dry snow) and to assess the variation of the resulting gauge catching performance with the wind speed. The collection efficiency obtained with the LES approach is generally lower than the one obtained with the RANS approach. This is because of the impact of the LES-resolved turbulence above the gauge orifice rim. The comparison between the collection efficiency values obtained in case of shielded and unshielded gauge validates the choice of installing a single Alter shield in a windy environment. However, time-dependent simulations show that the propagating turbulent structures produced by the aerodynamic response of the upwind single Alter blades have an impact on the collection efficiency. Comparison with field observations provides the validation background for the model results.
机译：通常使用挡风玻璃来减少风对降雪测量的影响。本文使用数值模拟研究了屏蔽和非屏蔽仪表的捕捉性能。在第二部分中，研究了挡风玻璃和仪表空气动力学特性以及由于防护罩-仪表配置产生的湍流而引起的变化流场在降低捕捞效率方面的作用。这是基于在第一部分中获得的计算流体动力学结果的基础上的，其中使用两种与时间无关的方法[雷诺平均Navier-Stokes（RANS）]，获得了非屏蔽和单个Alter屏蔽Geonor T-200B仪表附近的气流模式。以及与时间有关的[大涡模拟（LES）]方法。拉格朗日轨迹模型用于跟踪不同类型的雪花（干雪和干雪），并评估所得标尺捕捉性能随风速的变化。 LES方法获得的收集效率通常低于RANS方法获得的收集效率。这是由于标准孔口边缘上方LES消除的湍流的影响。在有屏蔽和无屏蔽仪表的情况下获得的收集效率值之间的比较验证了在大风环境中安装单个Alter屏蔽的选择。但是，随时间变化的模拟表明，由逆风单个Alter叶片的空气动力响应产生的传播湍流结构会对收集效率产生影响。与现场观察的比较为模型结果提供了验证背景。

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