Distributed observations of wind direction using microstructures attached to actively heated fiber-optic cables
Distributed observations of wind direction using microstructures attached to actively heated fiber-optic cables
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DOI：
10.5194/amt-13-1563-2020
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发表时间：
2020-04-01
影响因子：
3.8
通讯作者：
Thomas, Christoph
中科院分区：
文献类型：
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作者：
Lapo, Karl;Freundorfer, Anita;Thomas, Christoph
弱风边界层的特点是湍流和亚中尺度运动，打破了必要的假设，使用传统的涡动协方差观测，如水平均匀性和平稳性，激发需要一个观测系统，允许空间分辨测量的大气流动表面附近。光纤分布式传感（FODS）有可能打开大门，观察范围广泛的大气过程的空间分布的基础上，迄今已被用来解决湍流领域的空气温度和风速的秒和分米的尺度。在这里，我们报告的进展发展FODS技术观测空间分布的风向。我们将锥形微结构固定在主动加热的光纤电缆上，方向相反，将方向敏感的对流热通量从光纤电缆施加到空气中，导致感应温度的差异取决于风向。我们展示了一系列微观结构参数，包括纵横比，间距和尺寸的行为，并开发了一个简单的确定性模型来解释作为风速的函数的温差。利用计算流体力学模拟和锥形光纤系统的红外图像，探索了方向敏感热损失背后的机制。虽然这里给出的结果仅与沿沿着观测风向有关，但它是朝着全三维分布式流量传感器的最终目标迈出的重要一步。
The weak-wind boundary layer is characterized by turbulent and submesoscale motions that break the assumptions necessary for using traditional eddy covariance observations such as horizontal homogeneity and stationarity, motivating the need for an observational system that allows spatially resolving measurements of atmospheric flows near the surface. Fiber-optic distributed sensing (FODS) potentially opens the door to observing a wide range of atmospheric processes on a spatially distributed basis and to date has been used to resolve the turbulent fields of air temperature and wind speed on scales of seconds and decimeters. Here we report on progress developing a FODS technique for observing spatially distributed wind direction. We affixed microstructures shaped as cones to actively heated fiber-optic cables with opposing orientations to impose directionally sensitive convective heat fluxes from the fiber-optic cable to the air, leading to a difference in sensed temperature that depends on the wind direction. We demonstrate the behavior of a range of microstructure parameters including aspect ratio, spacing, and size and develop a simple deterministic model to explain the temperature differences as a function of wind speed. The mechanism behind the directionally sensitive heat loss is explored using computational fluid dynamics simulations and infrared images of the cone-fiber system. While the results presented here are only relevant for observing wind direction along one dimension, it is an important step towards the ultimate goal of a full three-dimensional, distributed flow sensor.