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

风沙主要是在跃变过程中输运的，其机理已从颗粒的跃变动力学和风动力与颗粒的耦合进行了研究。至于前者，人们一直在关注的事实是，个体的跳跃是由于床上的碰撞和排斥而继续进行的。而对于后者，分析中着重考虑了风的动量被提供给颗粒加速的事实，并在分析中考虑了空间平均阻力及其作为弥散障碍物产生的额外湍流能量所做的功。研究结果较好地解释了风沙和风沙的性质。其次，对风沙的非平衡输运和风速剖面的发展进行了讨论，以便将理论应用于植被存在和沙层变形的实际情况。在风洞中进行了一些简单的算例，验证了理论的正确性。风沙输沙率的测量对于风沙输沙率的现场应用非常重要。当使用水平沙池时，风向应足够长，但通常很难提前知道风向。在这项研究中，采用了纵向和横向网格相结合的沙漏。每个网格中沉积的沙量取决于风强和风向。基于本研究阐明的风沙运动理论，推导出了一种由各网格中沙粒沉积的分布来确定风向和风沙输移率的方法，并通过风洞试验验证了该方法的准确性。

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.