探空湿度测量防雨帽优化设计仿真研究

Simulation Study on Optimal Design of Rain-proof Cap for Radiosonde Humidity Measurement

当前常用探空仪湿度测量系统绝大部分都带有防雨帽,湿度测量也明显存在太阳辐射偏干误差(SRDB)。为研究和改善防雨帽对湿度测量造成的影响,采用流体动力学方法研究了常见圆柱形、棱形以及半球形3种结构防雨帽对湿度测量的影响,对比了不同材料的防雨帽对SRDB的影响。通过Pro/E软件建立高空湿度测量系统三维模型,借助ICEM将模型进行网格划分,通过Fluent软件模拟各条件下湿度传感器在太阳辐射下的温升情况,结合饱和水汽压公式推导湿度测量的SRDB。结果表明:3种结构的防雨帽在防雨效果方面效果相当;在防辐射方面,圆柱形防雨帽表现较好,采用防水透气膜代替传统塑料的防雨帽,能够最大程度地降低探空仪湿度测量的SRDB,为防雨帽的优化设计提供一定的参考。

At present, most of the humidity measurement systems of radiosonde are equipped with rain-proof caps. There is obvious solar radiation dry bias(SRDB) in humidity measurement. In order to study and reduce the error caused by the rain-proof cap on the humidity measurement system, the influence of three kinds of rain-proof caps with common cylindrical, prismatic and hemispherical structures on humidity measurement is studied by using fluid dynamics method. And the influence of rain-proof caps made of different materials on SRDB is compared. An three-dimensional model of high altitude humidity measurement system is established by Pro/E software. Then the model is meshed with ICEM. Finally, the temperature rise of humidity sensor caused by solar radiation under various conditions is simulated by FLUENT software, and the SRDB of humidity measurement is derived combined with Goff-Gratch approximation formula of saturated vapor pressure. The numerical simulation results show that three kinds of rain-proof caps have the same effect on rainproof effect. However, in terms of radiation protection, the cylindrical rain-proof cap is better than the other two kinds. The SRDB of radiosonde humidity measurement can be minimized using rain-proof cap with waterproof and breathable membrane instead of the one with traditional plastic, which provides some theoretical basis for the optimal design of the rain cap.