跃移沙粒运动参数的数字图像分析

Digital Image Analysis on Motion Parameters of Saltating Sand Grains

采用高速相机记录了大气边界层风洞中的沙粒跃移运动,并对所获取的跃移图像序列运用双向粒子追踪算法对帧间沙粒进行匹配,从中提取出准确的跃移轨迹.对跃移沙粒位置函数进行基于时间自变量的曲线拟合及求导来计算运动参数,结果表明,与传统方法及降频差分法相比,拟合-求导法能更好地克服数据波动性大、端点数据损失及时间分辨率低等问题,在单颗粒连续性运动量化分析中更具实际意义.结合拟合-求导法和简化受力模型,计算得出了真实跃移过程中阻力加速度的变化以及广义升力在来流方向的作用方式.

A high-speed digital camera was adopted to record the saltation of sand grains in an atmospheric boundary layer （ABL） wind tunnel. The bidirectional particle tracking algorithm was employed in matching interframe particles and Abstracting trajectories from image sequence. The time based curve fitting and the derivation were applied to calculate motion parameters for the position function of sand particle saltation. Compared with conventional and frequency reduced discrete difference methods,the present curve fitting and continuous derivation method is more effective in single-particle continuous motion analysis. Moreover,the drag acceleration and the way of the general lift force in wind direction are achieved.