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

• 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
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63550375/
• 关键词: Bed Load; Critical Tractive Force; Mixed Bed; Fluid Force; Incipient Motion; 流砂; 移動限界掃流力; 抗力・揚力; 流体力変動; 土砂水理学; 移動限界; 混合砂礫; ピックアップレート

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.

本文首先对三种砾石模型的流体力特性进行了实验研究，分别从阻力和升力的时均值和波动值两个方面进行了分析。其次，从理论上分析了砾石脱离沉积物床面的过程，推导出了砾石脱离沉积物床面的临界牵引力公式。(1)砾石层顶处的流速作为流体力的代表流速最为恰当。(2)升力时均值与阻力时均值之比不受相对深度的影响，但随突出率的变化而变化很大。(3)定量地阐明了球形和短圆柱（圆形和椭圆形截面）的阻力系数和升力系数的特性。(4)阻力和升力脉动的概率密度可用高斯正态分布函数很好地近似。(5)定量地阐明了流体力波动的标准差与突出率之间的关系。(6)在理论研究中，利用流体力的一些假设，对球形砾石在紊流作用下沿斜坡滚动的行为进行了公式化和求解。(7)推导出的临界牵引力方程中包含了牵引率作为帕拉之一，因此方程给出的值的物理意义是明确的。(8)通过实验验证了该方程的有效性。

项目成果

OKABE, TAKESHI・NAKANO, SUSUMU・YOSHIDA, HIROMU: "Fundamental Study on Incipient Motion of Coarse Particles in Mixed-Sediment Beds" Proceedings of Hydraulic Engineering, JSCE. Vol. 35. (1991)

OKABE、TAKESHI・NAKANO、SUSUMU・YOSHIDA、HIROMU：“混合沉积层中粗颗粒初始运动的基础研究”水利工程学报，JSCE 第 35 卷。

岡部 健士,中野 晋,吉田 弘: "混合砂礫床の粗粒成分の移動限界に関する基礎的研究" 水工論文集. 35. 397-402 (1991)

Kenji Okabe、Susumu Nakano、Hiroshi Yoshida：“混合砂砾层中粗粒成分运动极限的基础研究”水利工程学报 35. 397-402 (1991)。

岡部健士,中野晋,吉田弘: "粗面上に突出した球に作用する流体力" 水工学論文集. Vol.34. (1990)

Kenji Okabe、Susumu Nakano、Hiroshi Yoshida：“作用于从粗糙表面突出的球体上的流体力”《水利工程学报》第 34 卷（1990 年）。

岡部 健士,中野 晋,吉田 弘: "粗面上に突出した球に作用する流体力" 水工論文集. 34. 499-504 (1990)

Kenji Okabe、Susumu Nakano、Hiroshi Yoshida：“作用于从粗糙表面突出的球体上的流体力”水利工程杂志 34. 499-504 (1990)。

OKABE, TAKESHI・NAKANO, SUSUMU・YOSHIDA, HIROMU: "Fluid force Acting on Sphere protruding from Rough Roundary" Proceedings of Hydraulic Engineering, JSCE. Vol. 34. 499-504 (1990)

OKABE、TAKESHI・NAKANO、SUSUMU・YOSHIDA、HIROMU：“作用于从粗糙圆形突出的球体上的流体力”，水利工程学报，JSCE 第 34 卷，499-504（1990 年）。