Studies on the laws for sand transport in bed load by waves, winds and currents

本文从理论上研究了波浪、风、流对床质输沙的作用规律，以期统一这些作用作用下的输沙机理。主要研究结果如下：1)提出了考虑剪切效应引起的虚质量力和抬升力的砂粒湍流动力响应理论。求解了沙粒在空气和水中湍流作用下的动力学响应特性。用该理论动态地推导了风沙运动阈值，理论结果与实验结果吻合较好。2)建立了沙粒在波浪、风、流作用下的跳跃或滑动运动动力学。得到了砂粒的运动特性。明确了虚质量力和波加速度的影响。(3)在跃变过程中，均质砂和级配砂对跃变砂粒与颗粒床的碰撞机理进行了动态描述。理论结果较好地解释了级配砂在风沙中的分布对级配砂输沙率的影响。4)应用动量守恒定律在跃变层中，在引入跃变特性的均匀条件下，从理论上推导了输沙率规律。计算公式与砂体输运试验数据吻合较好。5)为了将均匀条件下的输砂率规律推广到非定常条件下的输砂率规律，推导了砂-液两相系统的控制方程。将其随水深从底部到水面积分，得到输沙速率的守恒方程。该方程是输沙率的广义表达式之一，可推广为风沙流输沙的基本理论。少

In this study, theoretical investigations of the laws for sand transport in bed load by waves, winds and currents were made in order to unify the mechanism of sand transport by these actions. The main results are:1) A theory of the dynamical response of sand grains to turbulence was proposed taking into account the virtual mass and uplift forces due to the shear effect. The dynamical response characteristics of sand grains to turbulence in air and water were solved. By this theory, the threshold of sand movement by waves, winds and currents were dynamically formulated and the theoretical results were in good agreement with experimental ones.2) The dynamics of motion of a sand grain as saltation or sliding by waves, winds and currents was established. The characteristics of the sand grain motion were obtained. The influence of the virtual mass force and wave acceleration force were made clear.3) In the saltation the mechanism of collision of a saltating sand grain to the granular bed wa … More s dynamically formulated both in uniform and graded sand. By the theoretical result, the influence of the distribution of graded sand on the transport rate of graded sand in blown sand was well explained with experimental and field data of sand transport.4) By applying the momentum conservation law in a saltation layer, the law for sand transport rates was theoretically formulated in the uniform condition introducing the saltation characteristics. The formulas agree well with experimental data of sand transport.5) In order to extend the law for sand transport rates in the uniform condition to that in the unsteady condition, the governing equations of sand -fluid two-phase systems were derived. By integrating it over the waterdepth from the bottom to the water surface, the conservation equations of sand transport rates were obtained. The equations are one of the generalized expression of sand transport rates and may be extended as the basic theory of sand transport by waves, winds and currents. Less