PIV法および直接数値計算法による流砂のマイクロメカニクスの解明

利用PIV方法和直接数值计算方法阐明流沙的微观力学

• 批准号: 13650575
• 负责人: WELLS John C.
• 金额: $ 2.05万
• 依托单位: Ritsumeikan University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13650575/
• 关键词: wall turbulence; bedload sediment transport; particle; collision; coefficient of restitution; simulation; Stereo PIV; micro-sensor; 衝突・接触モデル; 直接数値計算法; 力・モーメントの測定

Toward the objective of understanding the micromechanics of bedload sediment transport, the present project had three objectives : (1) Development and validation of a numerical method to simulate the motion of many solid particles in a turbulent flow, (2) Development and validation of a micro force-moment sensor, (3) Clarification of the microdynamics of bedload particle motion.Concerning objective (1) : To perform simulations of the type envisaged, it is necessary to develop an accurate model for the forces between particles in water, in particular the viscous "lubrication" force. To that end,we dropped glass beads vertically onto a stainless steel plate whose roughness was varied over two orders of magnitude, from 1 to 100 microns. Contrary to previous theoretical arguments, we found that roughness decreased the coefficient of restitution, and by an amount that was similar in air and water, which suggests that energy dissipation is dominated by plastic deformation within asperities of the solid material. In other work, we have proposed an important variation of Kajishima's method of simulating solid particles in a turbulent flow (ref. 1 below).Objective (2) : We have micromachined chips with a crossbar structure capable of measuring all 6 components of force and moment applied to the structure. A test particle can be mounted thereon, and installed at the bottom of a water channel. Tests with the particle half-emerging from the bed plate have achieved a fairly reproducible signal down to ReT of 300(ref. 6 below).Objective (3) : We have performed DNS of turbulent flow in a smooth-bed channel flow with a surface-mounted hemisphere. We found an extremely high correlation between the lift on the hemisphere, its drag, and the nearby streamwise velocity component (ref. 2 below). We also found very different skewness of forces on a hemisphere of diameter d+=12 vis-a-vis a diameter of d+=33. 10. KEY WORDS

为了了解床质沉积物输送的微观力学，本项目有三个目标：(1) 开发和验证模拟湍流中许多固体颗粒运动的数值方法，(2) 开发和验证微力力矩传感器，(3) 澄清床载颗粒运动的微动力学。关于目标 (1)：为了执行设想类型的模拟，有必要为颗粒之间的力开发一个精确的模型。水，特别是粘性的“润滑”力。为此，我们将玻璃珠垂直落到不锈钢板上，不锈钢板的粗糙度变化了两个数量级，从 1 微米到 100 微米。与之前的理论论证相反，我们发现粗糙度降低了恢复系数，其降低程度在空气和水中相似，这表明能量耗散主要由固体材料粗糙度内的塑性变形决定。在其他工作中，我们提出了鹿岛模拟湍流中固体颗粒方法的一个重要变体（下面的参考文献 1）。目标 (2)：我们拥有具有横杆结构的微机械芯片，能够测量力和力的所有 6 个分量。施加到结构上的力矩。可以将测试颗粒安装在其上，并将测试颗粒安装在水道的底部。使用从床板中出现的半颗粒进行的测试已经获得了低至 300 ReT 的相当可重复的信号（下面的参考文献 6）。 目标 (3)：我们使用表面安装的半球。我们发现半球的升力、阻力和附近的流向速度分量之间存在极高的相关性（下面的参考文献 2）。我们还发现，直径为 d+=12 的半球与直径为 d+=33 的半球上的力的偏斜度非常不同。 10. 关键词