气流中跃移颗粒的受力分析

Mechanical Analysis of a Single Saltating Particle in Air Flow

气流中颗粒跃移过程中的受力分析及其运动机理的研究在发展风沙物理学理论方面具有重要的意义。长期以来，受实验条件和实验手段的限制，关于此方面的认识还不统一。采用高速频闪摄影技术，在计算跃移颗粒各运动参数的基础上，反推出跃移颗粒的阻力系数和升力系数，并将颗粒所受的阻力、升力和重力进行了比较。结果表明，阻力最重要，重力次之，升力也不可忽略，它占重力的２０ ％ 以上。利用数值计算方法，得出了颗粒的跃移运动轨迹，与实测资料基本一致。

Mechanical analysis of a single saltating particle in air flow and its motion mechanism play an important role in development the Physics of Wind blown Sand. By means of high speed multi flash photography, this paper analyzes the variation law of drag coefficient and lift coefficient of saltation particle, and makes a comparison between drag, lift force and gravity force. Conclusions are as follows. First, drag coefficient of sand particle is different from one of idealistic small sphere. Second, among all forces, drag whose values can reach several times of gravity force is the most important, gravity force lists second, and lift force which accounts for more than 20% is not negligible. Third, using numerical method, saltating trajectory of sand particle has been obtained. Comparison of computed trajectory and measured trajectory shows that mechanical analysis discussed forward is very reasonable. Last but not least, sand particle may be subject to other forces similar to Magnus or Saffman lift forces.