| In recent years,with the rapid development of chemical industry,the use of chemicals is more and more.Among them,because of the incorrect storage,some of the chemicals cause leakage accidents,producing gas greater than the density of air,which called heavy gas,spreading along the surface,leading to a sharp rise in the probability of occurrence of toxicosis,fire,explosion and other dangrous accidents,seriously threatening personal safety and property safety of surrounding people.Heavy gas dispersion is affected by many external factors,such as wind speed,obstacles and so on,which process is very complex.Therefore,developing research on heavy gas dispersion process has important theoretical value and practical significance for scientifically preventing the occurrence of heavy gas leakage accident and guiding the emergency rescue.The process of heavy gas dispersion is fairly complex,large scale field tests study can collect a large number of real data,but costly and cannot be repeated,the applicability of empirical model is narrow and precision is not enough.To solve above problems,this article use computational fluid dynamic(CFD)model which is decorated by the modified turbulence(k-ε)model,taking chlorine gas as an example,to develop study on heavy gas dispersion around obstacles in windy conditions.The main research work of this paper is as follows:(1)The author summarized the current research situations of numerical model for heavy gas dispersion,after comparing and analyzing advantages and disadvantages of phenomenological model,box model,shallow model and computational fluid dynamics model,choose the latter to simulate the process of heavy gas dispersion,and more realistically describe the turbulent motion in this process by modified turbulence model.Select experimental scenes,and establish a three-dimensional coordinate system,combining the coordinate system,and then establish mathematical equations of the CFD model,simplify formulas to be solved.(2)When solving CFD numerical model,because of the great number of grids in the calculation area,the computing task is arduous and time-consuming.At present,in the field of high performance computing,the CPU-GPU heterogeneous architecture has been developed rapidly,which has been paid more attention by many scholars due to its huge parallel computing potential.However,the OpenCL programming model of CPU-GPU heterogeneous system lack of ability to extended to multiple computing nodes,traditional parallel programming models,such as shared memory programming model OpenMP,is difficult to excavate the computing power of heterogeneous systems,so,combining OpenCL and OpenMp,using MPI as the message passing mechanism between processes,this paper provides a three-level hybrid parallel programming model based on MPI+OpenMP+OpenCL,in order to optimize the process of CFD numerical model,greatly improving the computing speed and accuracy,and ensuring the real-time computing.When the size of grids are 200*200*80,the model contains 12.56 speedup on 128 computing nodes,and the parallel efficiency is about 62.1%.(3)Combining numerical results of CFD model with 3D simulation software Unity3D,real-timely simulates the process of chlorine dispersion under the condition of wind around obstacles,the simulation results are true and beautiful,animation effect is smooth and natural.In addition,according to the concentration of chlorine,mapping the damage area and giving risk assessment of chlorine toxicosis accidents by combining damage model with personal risk. |
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