Critical Tractive Force of Very Large Gravels on Mountainous River-Bed

山地河床上特大砾石的临界牵引力

基本信息

批准号：
63550375
负责人：
OKABE Takeshi
金额：
$ 0.32万
依托单位：
The University of Tokushima
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

项目摘要

In this study, at first, the characteristic of fluid force acting on three types of gravel model was investigated experimentally with respect to both the time averaged and flactuating values of the drag and lift. Secondly, the process of the escaping phenomena was considered theoretically and an equation for the critical tractive force of an isolated gravel protoruding from sediment bed with an arbitrary protrusion hight.The Summary of the Results of this Research is as Follows.(1) The velocity at the hight of the top of gravel is most pertinent as the representative velocity of the fluid force.(2) The rate of the time-averaged value of lift to that of drag is not affected by relative depth but greatly varies with the change in protrusion rate.(3) The characteristics of drag and lift coefficients of sphere and short columns (circler and elliptical cross sections) were quantitatively clarified.(4) The probability density of the fluctuation of drag and lift is well approximated by the Gauss's normal distribution function.(5) The relation between the standard deviation of the fluid force fluctuation and the protrusion rate was also clarified quantitatively.(6) In the theoretical consideration, the behavior of a spherical gravel which rolls up a slope under the effect of turbulent flow was formulated and solved by the use of some assumptions for fluid force.(7) The deduced equation for the critical tractive force includes the pick-up rate as one of the para meters, and therefore the physical meaning of the value given by the equation is distinct.(8) The Validity of the Equation was Confirmed Experimantally.

在这项研究中，首先，对作用于三种类型的砾石模型的流体力的特征进行了实验研究，相对于阻力和提升的平均时间和裂变值。其次，从理论上讲，逃脱现象的过程被认为是从沉积物床上带有任意突出的临界碎石蛋白质的临界拖拉力的方程式。该研究结果的摘要如下。（1）速度在砾石顶部的高处是流体力的代表性速度。（3）定量阐明了球体和短柱（圆形和椭圆形横截面）的阻力和升力系数的特征。功能。（5）流体力波动的标准偏差与突起速率之间的关系也被定量阐明。（6）在理论上考虑的是，球形砾石的行为在湍流的效果下向斜坡卷起通过使用一些假设用于流体力来制定和求解。（7）临界拖拉力的推导方程式包括拾取率作为para仪表之一，因此，方程式给出了值的物理含义。（8）实验证实了方程的有效性。