沙波迎流面流速分布公式

Velocity distribution of nonuniform flow on the stoss side over dunes

为进一步揭示沙波水流运动特性及提高沙波迎流面流速计算精度,采用两种概化模型,通过小水深沙波水槽试验,运用声学多普勒流速仪,对沙波沿程及垂线流速分布进行了测量。基于乐培九次生流理论公式,结合沙波水流特性,假定次生流在沙波迎流面上处于一个不断发展演变的过程,提出了发展函数和修正函数,得到了适用于沙波迎流面的流速垂线分布公式。研究结果表明:相对水深越小,沙波地形对迎流面水流作用越显著,使得上部流速减小、近底流速增大,且越靠近波峰这种现象越明显;建立的沙波流速公式与实测值吻合较好,能够准确地反映出迎流面流速变化规律。

In order to further reveal the flow characteristics over dunes and thus improve the calculation accuracy of velocity, the time-mean velocity profile was analyzed both experimentally and theoretically, and the instantaneous ve- locities were measured over two different forms of dunes at a shallow depth by virtue of Acoustic Doppler Velocimeter （ ADV）. Based on the secondary flow formula proposed by Yue, together with the flow characteristics of dunes, a for- mula of velocity vertical distribution over dunes, including the functions of development and correction, was put for- ward on the premise that the secondary flow on the stoss side was a continuous evolution process. The results showed that the effects of dunes on incident flow surface became more significant with the decrease of relative depth of water, which made the upside velocity decrease and near-bed velocity increase. By comparison with flume experimental data, the proposed formula had a good agreement with measured values, which could well describe the velocity profile.