摘要
利用风洞实验研究风力作用下颗粒阻力系数变化规律。以乒乓球（直径3.9 cm）模拟自然界大颗粒,采用三分量传感器直接测量颗粒水平受力,并与表面风速测量同步进行,采样频率设为125 Hz。结果表明：颗粒水平阻力与颗粒表面风速的变化趋势一致,并随着来流风速及高度的增加而增大;在实验范围内（雷诺数约在9 000~40 000）,水平阻力（Fx）与表面风速（Ux）的关系符合Fx=0.514（1/2AρU2x）＋0.019,式中A为颗粒的迎风投影面积,ρ为空气密度,取1.285 kg·m-3,可以看出,阻力系数CD为0.514,略大于水流中颗粒的阻力系数CD值（0.44）;常数项0.019表明其他力（如附加质量力和历史作用力等）的作用不可忽略。
Wind tunnel experiments were conducted to study the variation of the drag coefficient of particle in turbulent layer. A ping-pong ball was selected to simulate particle. The horizontal drag force on the ping-pong ball was measured by three-component accelerometer. The wind velocity around particle was measured synchronously and the sample frequency was set to 125 Hz. Advanced devices were used to measure both the horizontal drag force exerted by wind on a particle and the wind velocity with different wind velocities and different heights.A new relation between horizontal drag force（Fx）and the horizontal wind velocity（Ux）is obtained. The calculations by the formula have good agreement with the observations. The formula provides a good way to predict the drag coefficient of particle in turbulent layer. The results show as follows：（1）The horizontal drag force has the same tendency with particle surface wind velocity and increases with the increasing wind velocity and height of particle position.（2）When the Reynolds number ranges from 9 000 to 40 000,the relation between horizontal drag force（Fx）and the horizontal wind velocity（Ux）can be written as Fx = 0.514（1/2AρU2x）＋0.019,where CD=0.514 is the horizontal drag coefficient. It can be seen from the equation that the drag coefficient CD=0.514 is larger than that in water flow field（0.44）. The constant term 0.019 in the equation indicates that the effect of other forces,for example,added mass force,history force,cannot be ignored. Overall,the variation of the drag coefficient in the water flow cannot be applied directly to that in the air flow. Further studies on the variation of the drag coefficient in the air flow are required. Although,the velocities measured in this paper could cover most real situations,the Reynolds number should be extended in order to understand the rule of the drag coefficient CD. In addition,the sand particle is represented by a ping-pong and the differences between them are apparent,for example,size,shape
出处
《干旱区地理》
CSCD
北大核心
2016年第5期1011-1017,共7页
Arid Land Geography
基金
国家自然科学基金项目(41171005)
宁夏回族自治区科技专项(201101-ZLYJ)
关键词
气流
水平阻力
阻力系数
风洞实验
drag coefficient
drag force
air flow
wind tunnel experiment
