单雨滴降落速度变化数值模拟

为了有效分析雨滴终速对土壤的溅蚀作用,利用Ansys/Fluent软件和VOF模型对雨滴进行自由跟踪,结合雨滴和薄层水混合模拟分析了雨滴降落过程中的速度变化和雨滴降落到水面的速度、雨滴直径和降落高度的关系,根据相关文献资料验证了模拟结果。结果表明:雨滴以相同直径下落时,随高度的增大,雨滴入水直径总体呈变小趋势,降落高度为15~20 m时,雨滴直径减小到原来的40%;在相同高度的条件下,随着雨滴直径的增大,雨滴入水直径呈增大趋势,当雨滴初始直径由3 mm增大至4 mm时,则入水雨滴直径增大20%;雨滴直径在2~4 mm范围内,当水层厚度达到2.5cm时,雨滴的打击力消失。

Numerical simulation of single raindrop landing speed change

In order to effectively analyze the effect of terminal velocity of raindrops on soil erosion, the Ansys/Fluent software and VOF model were used to track raindrops freely, and the simulation of mixing rain and thin layer of water was conducted to analyze velocity changes of raindrops and the connection between velocity, raindrops diameter and height when raindrops fall to the surface of the water. The simulation results were verified based on relevant literature data. Results show that when the raindrops fall with a same diameter, along with the increase of height, the diameter of raindrops entering the water showed a trend of decrease, decreasing from the diameter of 15 m to 20 m to 40% of the original diameter.Under the condition of the same height, with the increase of diameter, the diameter of raindrops entering the water showed a trend of increase, increasing by 20% from diameter of 3 mm to 4 mm . When raindrops diameter was within 2 mm to 4 mm, and water layer thickness was 2.5 cm, raindrops hiting power disappeared.