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Mechanism of blown sand with vegetation of coastal area from multi-phase flow dynamics and methods of blown-sand control

从多相流动力学角度探讨沿海植被风沙机理及风沙控制方法

基本信息

批准号：
08650593
负责人：
TSUJIMOTO Tetsuro
金额：
$ 1.28万
依托单位：
Nagoya University (1997)Kanazawa University (1996)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

Blown sand is dominantly transported in saltation, of which mechanism has been studied by coupling dynamics of saltating particles with wind dynamics with particels. As for the former, the fact that individual saltations are continued by colision and repulsion at the bed one another has been focused on. While for the latter, the fact aht the momentum of wind is provided into acceleration of particles has been focused on, and spatially averaged drag force and its work done as additional production of turbulent energy due to dispersive obstacles have been taken into account in the analysis. The result can explain the properties of blown sand and wind well.Next, non-equilibrium transport of blown sand and development of wind-velocity profile have been discussed in order to apply the theory to the actual situuation where the vegetation exists and sand bed is deformable. Some simple examples have been tested in a wind tunnel to verify the theory.On application of the idea to the fields, the measurement of blown sand transport rate is important. When one use a horizontal sand trap is employed, it should be long enough in the wind direction, but usually it is difficult to know the wind direction in advance. In this study, a sand trap with logitudinal and transverse meshes are employed. The amount of sand deposited in each mesh is distributed dependent of wind intensity and direction. Based on the theory of blown-sand motion clarified by this study, a method to know the wind direction and blown-sand transport rate from the distribution of sand deposition in each mesh is derived, and accuracy of this method has been certificated by wind tunnel tests.

风沙运动以跃移运动为主，通过跃移颗粒动力学和风动力学的耦合研究了跃移运动的机理。对于前者，着重于单个跃移通过床面相互碰撞和排斥而得以延续的事实，而对于后者，着重于风的动量提供给颗粒的加速的事实，并考虑了空间平均拖曳力及其作为弥散障碍物的附加湍流能的产生所做的功。本文还讨论了风沙的非平衡输运和风速廓线的发展，以便将理论应用于有植被存在和沙床可变形的实际情况。通过风洞试验验证了理论的正确性，并指出在实际应用中，风沙输沙率的测量是一个重要的问题。当一个人使用水平集沙器时，它应该在风向上足够长，但通常很难提前知道风向。在这项研究中，一个沙陷阱与对数和横向网格。沉积在每个网格中的沙的量分布取决于风的强度和方向。根据本文所阐明的风沙运动理论，推导出了由各网格的积沙分布来确定风向和风沙输运率的方法，并通过风洞试验验证了该方法的准确性。