﻿ 一种微下击暴流的实时仿真及可视化方法 A Real-Time Simulation and Visualization of the Microburst

Computer Science and Application
Vol. 08  No. 10 ( 2018 ), Article ID: 27285 , 11 pages
10.12677/CSA.2018.810176

A Real-Time Simulation and Visualization of the Microburst

Jun Zhang1,2, Kaiwen Chen1

1School of Digital Media, Jiangnan University, Wuxi Jiangsu

2Jiangsu Key Laboratory of Media Design and Software Technology, Jiangnan University, Wuxi Jiangsu

Received: Oct. 4th, 2018; accepted: Oct. 19th, 2018; published: Oct. 26th, 2018

ABSTRACT

The microburst is a special meteorological condition that affects the flight heavily. It threats to the aircraft seriously during takeoff and landing. A real-time visually simulation method of the microburst was presented to generate vivid 3D wind field for the flight simulation software or game. It may be used to improve pilots’ ability to deal with unexpected microburst situation. The presented method used a circle’s tangent model as a simplified mathematical approximation of the microburst. The simulated wind field was visualized by the common particle system overlapped a polygon trailing component. Experimental simulation scenes on the Unity engine show that the proposed method is easy to program and achieves real-time frame rate on a common PC.

Keywords:Microburst, Flight Simulation, Real-Time Simulation, Particle System, Visualization

1江南大学数字媒体学院，江苏 无锡

2江南大学江苏省媒体设计与软件技术重点实验室，江苏 无锡

Copyright © 2018 by authors and Hans Publishers Inc.

1. 引言

2. 微下击暴流仿真算法

2.1. 基于涡环的数学模型

Michael Ivan [2] 最早根据气象观测数据提出基于涡环的微下击暴流仿真模型，其仿真结果与实测风场数据在视觉上具有较高的一致性，得到广泛应用。

$\left\{\begin{array}{l}{\left(x-{x}_{p}\right)}^{2}+{\left(y-{y}_{p}\right)}^{2}={R}^{2}\\ z={z}_{p}\end{array}$ (1)

${\psi }_{p}=\frac{\Gamma }{\text{2π}}\left({r}_{\mathrm{max}}+{r}_{\mathrm{min}}\right)F\left(k\right)$ (2)

$\left\{\begin{array}{l}{v}_{x}=\frac{{x}_{A}-{x}_{P}}{{r}_{p}}{v}_{r}\\ {v}_{y}=\frac{{y}_{A}-{y}_{P}}{{r}_{p}}{v}_{r}\\ {v}_{z}=-\frac{1}{{r}_{P}}\frac{\partial \left({\psi }_{I}+{\psi }_{P}\right)}{\partial r}\end{array}$ (3)

Figure 1. The sketch illustration of the vortex ring model

Michael Ivan模型在计算上存在较大复杂度，对特殊位置(如主涡环自身和涡环中轴线等)存在奇异性问题，需要追加计算步骤。虽然后续研究者不断提出改进方案，但在计算速度上和程序复杂度上效果并不理想。

2.2. 本文圆切线模型

Michael Ivan模型采用涡环的主要原因是微下击暴流表现出典型的涡流现象，即风场存在一个旋转中心点，而方程(2)的切线方向与涡流现象吻合。方程(2)及其切线防线的计算复杂性是Michael Ivan模型复杂度的主要来源，本节提出使用圆切线的方式大幅降低模型复杂度。

Michael Ivan模型中计算涡环切线的过程，可以由图2中圆切线近似逼近，即风场在任意一点P的风矢量的方向与圆切线一致，大小与圆心距离调整：

$\left\{\begin{array}{l}{v}_{x}^{P}=\left(\frac{\left({y}_{p}-{y}_{B}\right)\varphi \left({d}_{B}\right)}{‖P-{O}_{B}‖}-\frac{\left({y}_{p}-{y}_{A}\right)\varphi \left({d}_{A}\right)}{‖P-{O}_{A}‖}\right)\stackrel{¯}{V}\\ {v}_{y}^{P}=\left(\frac{\left({x}_{P}-{x}_{A}\right)\varphi \left({d}_{A}\right)}{‖P-{O}_{A}‖}-\frac{\left({x}_{p}-{x}_{B}\right)\varphi \left({d}_{B}\right)}{‖P-{O}_{B}‖}\right)\stackrel{¯}{V}\end{array}$ (4)

Figure 2. The sketch illustration of the circle’s tangent model

3. 基于粒子系统的风场可视化技术

3.1. 粒子系统

$\left\{{\Theta }_{k}|{\Theta }_{k}=\left(\begin{array}{cccc}{x}_{k}& {y}_{k}& {z}_{k}& {t}_{k}\end{array}\right),k=1,2,\cdots ,N\right\}$ (5)

${\Theta }_{k}←\left(\begin{array}{c}{x}_{k}+{v}_{x}^{{\Theta }_{k}}\Delta t\\ {y}_{k}+{v}_{y}^{{\Theta }_{k}}\Delta t\\ {z}_{k}+{v}_{z}^{{\Theta }_{k}}\Delta t\end{array}\right)$ (6)

3.2. 拖尾技术

$\begin{array}{l}{T}_{0}={\Theta }_{k}\\ {T}_{k}={T}_{k-1}\end{array}$ (7)

4. 仿真实验结果

Figure 3. Description of trailing algorithm

(a) Michael Ivan模型仿真风场 (b) 本文方法仿真风场

Figure 4. Comparison of the simulated wind field

(a) 参数设置一 (b) 参数设置二(c) 参数设置三

Figure 5. Simulated wind field under different parameter settings

Figure 6. Visualization results by traditional graph-based method

Figure 7. Visualization results by traditional stream-line-based method

Figure 8. Visualization results by traditional convolution-based method

Figure 9. Visualization results by our trail-based method

Figure 10. A high lighted trail

Figure 11. Visualization results in a real 3D scene I

Figure 12. Visualization results in a real 3D scene II

Figure 13. Visualization results in a real 3D scene III

5. 结论

Figure 14. A simulated and visualizated Microburst in a flight simulation scene

Figure 15. Visualization results by the heat distortion trails

A Real-Time Simulation and Visualization of the Microburst[J]. 计算机科学与应用, 2018, 08(10): 1602-1612. https://doi.org/10.12677/CSA.2018.810176

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21. NOTES

1请查看在线视频，其动态效果更佳直观。https://www.bilibili.com/video/av31249132/