基于高速摄像技术的流体作用力试验

Experimental Investigation of Fluid Forces Using High-speed Imaging Technology

针对颗粒在动水中的流体作用力问题,采用高速摄像技术对颗粒的运动过程进行观测,通过求解圆球及天然泥沙跃移运动过程中的力学方程,得到拖曳力系数及上举力系数。试验结果表明:①动水中颗粒非匀速运动时的拖曳力系数、静水中颗粒非匀速运动时的拖曳力系数与匀速运动时的拖曳力系数均随着雷诺数的增加而减小,颗粒与水流之间的相对运动速度越接近于颗粒沉速,三者间的差异越小;当颗粒与水流之间的相对运动速度等于颗粒沉速时,三者近似相等。②形状对上举力系数的影响较对拖曳力系数的影响更明显,天然泥沙的拖曳力系数大于圆球的拖曳力系数,天然泥沙的上举力系数小于圆球的上举力系数。最后,构建了圆球及天然泥沙的拖曳力系数及上举力系数公式,公式计算值与实测值符合较好。

Particle motion was observed using high-speed imaging technology to investigate the fluid forces acting on particles in flowing water.The drag coefficient and lift coefficient were obtained by solving the mechanical equations for saltating spheres and natural sediments.Experimental results manifest that:1)The average drag coefficient for particles with nonuniform velocity in flowing water,particles with nonuniform velocity in stilling water,and particles with uniform velocity in stilling water all decrease with the increase of Reynolds number.The difference between these coefficients diminishes when the particle-fluid relative velocity approaches the settling velocity.When the relative velocity equals the settling velocity,the coefficients are approximately equal.2)Shape has a greater influence on lift coefficient than on drag coefficient;natural sediments exhibit larger average drag coefficient compared to spheres,whereas spheres demonstrate higher average lift coefficient than natural sediments.The equations for drag coefficient and lift coefficient of spheres and natural sediments are established,and the calculated values agree well with measured data.