飛砂運動的模擬及其編籬定砂的應用

Abstract

海岸風砂破壞當地環境、阻礙生物生長及破壞結構物等，嚴重影響國家經濟發展，為保護現地環境，加速國家經濟發展，本文進行海岸風砂研究，將砂體假設為球狀物，模擬砂體受力後的移動軌跡，了解旋轉砂體於流場中運動情況。 砂體於空氣流場中移動受到各種作用力影響(包含阻力、升力、浮力、重力、Magnus力、Saffman力等)，導致砂體有不同的移動軌跡，利用不同作用力計算，模擬砂體於空氣中之移動情況，比較與實際砂體運動軌跡，以了解各種作用力對砂體移動的影響大小，經比對後可知砂體於流場中同時考慮阻力、重力及Magnus力與實際量測出砂體運動軌跡較為接近，並可得知物體於流場中移動主要受到阻力、重力及Magnus力的影響。 加入機率因素的分佈探討，可以知道砂體飛行高度主要分布在30cm以下，撞擊後角度在90度以下，飛行中的砂體大多為低轉速，撞擊後速度主要在2 m/s以下。 本文提供沙體路徑計算的方式以及其機率分佈，以應用於防砂結構物的設計依據，減少海岸風砂問題。

The coast aeolian sand damages the environment and structures. It hinders biological growth and impacts the country's economic development seriously. For protecting the environment from damage and accelerating the country's economic development, this paper assumes the sand as spherical objects to simulate sand movement trajectory with various force and understand the rotation sand movement in the flow field. The sand bears various force (including resistance force, lift force, buoyancy force, gravity force, Magnus force, Saffman force, etc.) which will affect the sand movement in the fluid. By different parameters, we can simulate the movement situation in the air fluid and compare with the actual trajectory to understand how does the various force affects the trajectory. After comparing the experiment result, we get that the resistance force, gravity force, Magnus force are the major impact factors of the sand trajectory. With the probability, the sand flying distribution is under the 30 cm. The angle after impacting ground is less then 90 degree and most of sand speed is under 2 m / s and has low angle velocity.

This study provides the method of a sand trajectory calculation in the fluid and the sand probability distribution to be applied on the wind anti-sand structure design. We can apply the structures to decrease the coast corrosion from the sand.