基于虚拟模型的雾滴与叶片的交互行为分析

该文针对现有雾滴与植物叶片交互行为的研究局限于水平叶片的问题,提出了一种基于试验的液滴与不同倾角的植物叶片交互行为的模拟方法,并设计了一种新的液滴弹跳方向计算方法。首先利用微距高速摄像机对液滴在不同倾角的叶片上的静态接触角大小做了精确测量,并拟合了其随叶片倾角增大的变化规律,然后以此将弹跳判定公式推广到0°~50°范围内任意倾斜的叶片上。在液滴弹跳方向计算上引入了蒙特卡洛法,代替了原有的镜面反射计算液滴弹跳方向。模拟结果表明该方法能够较真实的模拟液滴与任意倾斜叶片的弹跳判定、碰撞、驻留以及飞溅现象。该文提出的方法,为研究雾滴与叶片的交互行为提供新的思路,使得模拟过程的计算量相对较小,为植物冠层与大量雾滴交互的沉积量计算和大规模植物场景与雾场交互的实施绘制提供了技术参考。

Behavior analysis of spray droplet interacting with plant leaves based on virtual model

Abstract: More scholars in recent years have interest in studying the interaction between spray droplets and leaves. However, due to limitations on the computational efficiency of the computer, the physical-based approaches to simulate the processes cannot meet the requirements on both rendering efficiency and considering physical laws at the same time. Aiming at the limitation of traditional simulation on interactions between droplets and leaves, which can only be applied to horizontal leaves, an experiment-based simulation method on interactions between droplets and any leaves, together with a new algorithm on bounce direction of droplets was proposed in this study in order to improve the situation of overly cost calculation time yet poor on accuracy on fluid mechanics of the popular spray models used currently. The interaction between droplets and leaves was simulated based on the experimental results in this paper by combining the improved algorithms based on the predecessors of existing formulas. As the first step, the macro-high-speed camera was used to monitor droplet on the leaf at different angles among 0°~50° of inclination, and measure its static contact angle size. Then the pattern of changes on the static contact angle of the droplet was fitted when the leaf inclination angle was increasing, and generalizing the existing bounce judgment formula to any inclined leaf. Finally, the Monte Carlo method was introduced to calculate the direction of droplet bounce. Instead of using the original specular reflection, the direction of droplet bounce was not in accordance with a single track to run, but turbulent as a sector, making it more consistent with the real environment. The simulation in this study was carried out on the platform of Windows8 Operating System, and using OpenGL to simulate the interaction between droplets and leaves. Simulation results showed that this method can reflect the physical law of collision, bounce judgment, dwell and splash of droplet with any inclined leaf. Besides, simulation in this study prevented the abuse of computational work load caused by the fluid mechanics formulas, and furthermore, the Monte Carlo perturbation was used instead of specular reflection ,making the simulation process in the calculation relatively small while at the same time being more in line with the actual physical laws. This study provides a new way to look into the interaction between droplets and leaves, supporting the calculation on the deposition amount of plant canopy interacting with a large number of droplets, and also possibilities for real-time rendering of large-scale plant scene and fog field interaction.