有毒重气扩散数值型优化与三维仿真研究

发布时间：2018-05-27 09:01

本文选题：重气扩散 + 数值模型　；参考：《北京交通大学》2017年硕士论文

【摘要】：近年来,随着化工产业的快速发展,化学品的使用越来越多。其中,一些化学品由于储存不正确,发生意外泄漏,产生比空气密度大的气云,称为重气,它沿着地表进行扩散,引发中毒、燃烧、爆炸等危险事故的概率急剧增加,严重威胁周围人员人身安全和财产安全。重气扩散过程受很多外界因素影响,如风速、障碍物等,其扩散过程复杂。因此,开展重气扩散过程的研究,对于科学预防重气泄漏引发事故的发生以及指导应急救援具有重要理论价值和实践意义。重气扩散过程相当复杂,大型现场试验虽然能够收集到大量的真实数据,但是花费巨大且不能重复试验,经验模型适用性较窄且精度不够。针对以上问题,本文选用修正的湍流(k-ε)模型修饰的计算流体力学(CFD)数值模型,以氯气为例,开展重气在有风条件下绕障碍物扩散的研究。本文主要的研究工作如下:(1)综述了重气扩散数值模型的国内外研究现状,在对比分析了唯象模型、箱模型、浅层模型和计算流体力学模型的优缺点之后,选用计算流体力学模型模拟重气扩散过程,并且选用修正的k-ε模型更为真实地刻画重气扩散过程中的湍流运动。选取实验场景,建立三维坐标系,结合坐标系建立CFD模型的数学方程式,简化公式待求解。(2)在求解CFD数值模型时,由于计算区域网格划分数目巨大,计算任务艰巨,耗时长。目前在高性能计算领域内发展非常迅速的CPU-GPU异构体系结构,其由于巨大的并行计算潜力被重多学者所关注。但是,CPU-GPU异构体系的OpenCL编程模型缺乏扩展到多个计算节点的能力,传统的并行编程模型如共享存储编程模型的OpenMP,又难以发掘异构系统所有的计算能力,所以本文将OpenCL与OpenMp结合起来,以MPI作为进程间的消息传递机制,提出基于MPI+OpenMP+OpenCL的三级混合并行编程模型,以此对CFD数值模型求解过程进行并行优化,大幅度提高计算速度和精度,保证计算的实时性。当网格规模为200*200*80时,该模型在128个计算节点上获得了 12.56的加速比,并行效率为62.1%。(3)将CFD模型的数值计算结果与三维仿真软件Unity3D结合,实时模拟氯气在有风条件下绕障碍物扩散的过程,仿真效果真实、美观,动画效果流畅自然。此外,根据氯气浓度绘制出伤害区域,结合伤害模型和个人风险,对氯气中毒事故给出风险评估。
[Abstract]:In recent years, with the rapid development of chemical industry, more and more chemicals are used. Among them, some chemicals are accidentally leaked due to incorrect storage, producing a gas cloud with a higher density than air, called heavy gas, which diffuses along the surface, causing a sharp increase in the probability of dangerous accidents such as poisoning, combustion, explosion, etc. It is a serious threat to the personal and property safety of the surrounding people. Heavy gas diffusion process is affected by many external factors, such as wind speed, obstacles and so on. Therefore, the research of heavy gas diffusion process is of great theoretical value and practical significance in preventing accidents caused by heavy gas leakage scientifically and guiding emergency rescue. The heavy gas diffusion process is quite complex. Although large scale field tests can collect a large amount of real data, it is expensive and cannot be repeated, and the applicability of the empirical model is narrow and the accuracy is not enough. To solve the above problems, the modified turbulence k- 蔚 model modified computational fluid dynamics (CFD) numerical model is used to study the diffusion of heavy gas around obstacles under the condition of wind, taking chlorine gas as an example. The main research work of this paper is as follows: (1) the present research situation of heavy gas diffusion numerical model at home and abroad is summarized. After comparing and analyzing the advantages and disadvantages of phenomenological model, box model, shallow model and computational fluid dynamics model, The computational fluid dynamics model is used to simulate the heavy gas diffusion process, and the modified k- 蔚 model is used to describe the turbulent motion in the heavy gas diffusion process more realistically. Selecting experimental scene, establishing three-dimensional coordinate system, establishing mathematical equation of CFD model combined with coordinate system, simplifying formula to be solved. (2) in solving the numerical model of CFD, because of the huge number of grid division in calculation area, the calculation task is arduous, and the time consuming is long. At present, CPU-GPU heterogeneous architecture, which has been developing rapidly in the field of high performance computing, has attracted much attention from many scholars because of its huge parallel computing potential. However, the OpenCL programming model of CPU-GPU heterogeneous system lacks the ability to extend to multiple computing nodes. The traditional parallel programming model, such as OpenMPof shared storage programming model, is difficult to exploit all the computing power of heterogeneous systems. Therefore, this paper combines OpenCL and OpenMp, takes MPI as the message passing mechanism between processes, proposes a three-level hybrid parallel programming model based on MPI OpenMP OpenCL, and optimizes the CFD numerical model solving process in parallel. The calculation speed and accuracy are greatly improved to ensure the real-time calculation. When the grid size is 200 / 200 / 80, the acceleration ratio of 12.56 is obtained on 128 computing nodes, and the parallel efficiency is 62.1. the parallel efficiency of this model is 62.1. the model combines the numerical results of the CFD model with the 3D simulation software Unity3D. The real time simulation of chlorine diffusion around obstacles under the condition of wind shows that the simulation effect is real, beautiful, and the animation effect is smooth and natural. In addition, according to the concentration of chlorine gas, the injury area is drawn, and the risk assessment of chlorine poisoning accident is given by combining the injury model and personal risk.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O241.82;O552.2

【参考文献】