Dynamical Evolution of Accidents Triggered by Major Hazard Installation(MHI) and Three-dimensional Reconstruction Technology of Disaster Scene
Author:Chen Wen Jiang
Supervisor:hu zhao ji
There are many major hazard installations(MHI)storing large amount of toxic,harmful,flammable and explosive substances in a chemical industrial park(CIP).They have the characteristics of distributivity and high risk.Once an accident occurs,MHI is likely to cause disastrous damage to the surrounding people,property and environment.Due to the limitations of the basic theories and technologies,the traditional methods of accident analysis and simulation mainly focus on reflecting the two-dimensional(2D)characteristics of accidents.However,for the major accidents,including leakage and diffusion,fire and explosion triggered by MHI,the three-dimensional(3D)characteristics always exist in the occurrence,evolution and consequence of accident.The title of this paper is Dynamical Evolution of Accidents Triggered by MHI and 3D Reconstruction Technology of Disaster Scene.The main research work and achievements can be summarized as follows:(1)According to the characteristics and storage conditions of the medium in MHI,the diffusion of flammable and toxic gas is one of the accident types that easily cause the evolution of accidents.Based on the basic idea of the stochastic simulation method,the leaking gas is considered to be a set of many random walking particles.The methods of analyzing the motion attributes(displacement and velocity,etc.)and the non-motion attributes(color,size,transparency,life cycle,etc.)of particles are proposed to establish the dynamics evolution model of flammable and toxic gas diffusion from 3D level.The simulation results show that the methods can exactly describe not only the 2D information of accident,but also the real-time 3D dynamics of the evolution process and consequence for the particle cloud under the influence of the surrounding environmental factors.(2)The thermal radiation is the main way for fire accidents triggered by MHI to destroy the surrounding environment.Based on the mechanisms of fire accidents,the dynamics models and the methods of evaluating the accident consequences,including jet fire,pool fire and fireball,are established in accordance with the thermal damage criterion of flame.The simulation results of fire accidents show that these models and methods can excellently reflect the 3D dynamic correlation among the state parameters of hazard medium,the characteristic parameters of flame shape,the surrounding environmental factors and the thermal radiation damage.(3)The energy from the impact loads including shock wave and fragments is the main form of explosive damage and further evolution.The impact damage models and methods of evaluating vapor cloud explosion(VCE)and boiling liquid expanding vapor explosion(BLEVE)are constructed by establishing the relationship among the explosion energy,the characteristic parameters of blast wave(peak overpressure,positive phase duration,lateral impulse,etc.)and the initial velocity of fragments.The simulation results of explosion accidents show that these models and methods can basically reflect the impact damage to the surrounding environment from shock wave and fragments.(4)According to the 3D characteristics of MHI accidents and the established model of accident damage,an organizational structure model of Multi-Agent-based system for accident simulation is established as well as a VR(virtual reality)-based technology for 3D reconstruction of MHI accident scene.Based on the model and technology,Assistant Decision-making System for Emergency of Accident Triggered by Regional MHI(ADS_MHI)is designed and developed to provide emergency rescue of accidents with the rapid,accurate and effective decision-making suggestions.The simulation results of accidents show that ADS_MHI can effectively achieve the tasks including information management and maintenance of MHI,dynamic supervision and risk early warning,accident consequence simulation,etc.During dealing with the tasks,ADS_MHI has good advantages of collaboration and intelligence to provide the reliable technology support for describing the 3D information of accidents in an all-round.It can be used as an information command platform for government and enterprises in the following aspects,such as safety supervision of MHI,accident prevention,emergency rescue and so on.(5)Taking the storage area of an enterprise as the typical MHI,ADS_MHI is used to simulate the accidents triggered by MHI.The process and the main work of simulation experiment are as follows: establishing a virtual scene in accordance with the actual geographic information in the storage area,real-time monitoring and accident risk early warning of MHI,analysis of potential accident,and 3D visualization simulation for the occurrence,evolution and consequence of accident.Finally,the effectiveness of ADS_MHI is evaluated and validated by comparing the simulation results of ADS_MHI with the international general experimental examples and the simulation results from the authoritative software packages named FLUENT,SAFETI and MHAU.The above research work establishes and improves the dynamic analysis model of MHI accident damage in theory,overcomes the limitations of traditional 2D methods,achieves the rapid 3D reconstruction of accident scene in technology,provides government and enterprises with reliable technology support and assistant decision-making suggestions in engineering to deal with MHI accidents.