风沙流中风速纵向脉动的实验研究

Longitudinal Intensity of Airflow Turbulence with Sand Grain Saltation in a Wind Tunnel

在4种风速条件下对风沙流中风速纵向脉动特性进行了风洞实验研究。研究发现,风速纵向脉动很大,不容忽视;脉动绝对大小随进口风速提高有增强趋势,随着高度的增加则变化不大;垂线脉动强度平均值随主流速度基本成正向线性关系;以脉动强度与当地风速之比表示的相对脉动强度随高度增加而降低,并且不同风速条件下相对脉动强度在床面附近相差较大,远离床面则趋向一致。另外,采用幂函数形式可较好地描述风沙流中平均风速的垂线分布。

The longitudinal intensity of airflow with sand grain saltation is studied experimentally in a wind tunnel. The experiments were conducted with one test sand and four different stream velocities. The four velocities tested were 8^5, 11^5, 13^5, and 22^5 m5s^(-1); measured at the centerline of the test section entrance. The mean grain diameter of the tested sand is 0^35 mm. The measurements show that the longitudinal turbulence intensity of airflow cannot be neglected. The turbulence intensity increase with the rise of stream wind velocity but keep a constant with height. The mean intensity of the turbulence is proportional to the free main velocity. The relative intensity of the turbulence defined as the ratio of turbulence intensity to mean wind velocity decrease with height. For different stream velocities, the relative intensity of the turbulence varies greatly in the near-bed region, and tends to be consistent outside this region.