风场对雨量计收集降水影响的流体动力学研究

CFD simulation of wind field impact on gauge precipitation

为研究风场对雨量计收集降水精确性的影响,对单个雨量计以及Alter和Tretyakov防风圈的风场特性进行数值模拟。结果表明:单个雨量计中心线上速度最大增比达19%,出现在器口上8 cm左右;加入Alter和Tretyakov防风圈可有效减少雨量计器口上方的风速大小和梯度:Alter防风圈使中心线上最大速度减小11%,并在主流方向90°位置产生两个强烈涡旋区域,破坏到达雨量计收集区域的流场强度和均匀性,使其流向较为紊乱,可能对降雪的收集产生不利影响;Tretyakov防风圈使雨量计中心线上最大速度减小7%,并由于叶片特殊勾角结构,使到达雨量计降水收集区域的流向更一致,更有利于对降雪的收集。Alter防风圈对风速大小和梯度的减弱程度优于Tretyakov防风圈,但低风速下Tretyakov防风圈在雨量计器口上方的涡核心区域范围小于Alter防风圈,更有利于降水收集。Tretyakov防风圈的直径比Alter防风圈小约0.3 m,如对Tretyakov防风圈进行改进,可增加其直径以及叶片个数来规避高风速下Tretyakov防风圈叶片产生的涡核心区域对雨量计收集区域的影响。对Alter防风圈改进,可参考Tretyakov防风圈,增加叶片倾斜角,以提高降水收集率。

To study the impact of wind field on the accuracy of a rain gauge,numerical simulation of the wind turbulence for a single rain gauge and gauges with Alter and Tretyakov wind shield was performed.The results show that the maximum velocity increase ratio of a single gauge on the center line can reach 19%,located 8cm above the gauge mouth.The Alter and Tretyakov wind shield can effectively reduce the intensity and gradient of the wind above the rain gauge mouth.The blades of the Alter wind shield can reduce the maximum velocity on the center line of the rain gauge by 11%.Two strong eddy regions are generated on the 90°of the main stream direction,which destroy the uniformity of the streamlines and reduce the continuity of the wind above the rain gauge.Due to the more turbulent wind field,there may be an adverse effect on snow collection.The Tretyakov wind shield can reduce the maximum speed on the center line of the rain gauge by 7%.The special angle structure of the blade makes the wind field in the collecting region more uniform,which is in favor of snow collection.The Alter wind shield is superior to the Tretyakov in reducing the wind speed and wind gradient,but the vortex core region of the Tretyakov at the top of the rain gauge is less than that of the Alter at low wind speed,which is beneficial to the precipitation collection.The diameter of the Tretyakov wind shield is about 0.3m smaller than that of the Alter.Therefore,the Tretyakov wind shield can be improved by increasing its diameter and the number of the blades to avoid the influence on the core area of the collecting region in the condition of high wind speed.The structure of the Tretyakov wind shield can be referred to improve the Alter wind shield and the influence on precipitation collection efficiency can be explored by increasing the angle of the blades.