Numerical Evaluation of Probability of Harmful Impact Caused by Toxic Spill Emergencies

Abstract

The purpose of the work is to assess the degree of inhalation damage of a person exposed to the toxic cloud of liquefied gas evaporation from a spill spot of various shapes. The mathematical model of liquefied gas spill evaporation which arose as a result of accidental destruction of the storage capacity and further dispersion of the gas impurity in the atmosphere surface layer was developed. The computational technology for determining the fields of conditional probability of human inhalation damage by a toxic gas based on a probit analysis is developed. The mathematical model takes into account the flow compressibility, complex terrain, three-dimensional nature of the dispersion process, and the presence of toxic liquid substance evaporation from the arbitrary spill spot with varying intensity. The model allows obtaining space-time distributions of the toxic gas relative mass concentration and inhaled toxidosis which is necessary to determine the fields of the human damage probability based on the probit analysis. For different ellipticity of the hydrogen cyanide spill elliptical spot the fields of probability of human mortal damage are obtained and the influence of spot ellipticity on the scale of the consequences of an accident of this type is analysed. The developed technology allows carrying out automated analysis and forecasting in the time and space of the damage probability of a person exposed to the toxic gas as an indicator of the safety of the technogenic object.

Numerical Evaluation of Wind Speed Influence on Accident Toxic Spill Consequences Scales

“…Spatial fields of damage probability can be used by safety experts to determine the risks of high danger industrial enterprises. In particular, it is possible to calculate the area of a zone hazardous for humans where the lethal conditional probability is greater than 50 %, and use this parameter as a scale of consequences for comparative computational experiments [30]. By repeating the computational process for different wind speeds, it is possible to achieve the aim of this study to determine the effect of wind speed on the environment consequences of an accidental spill of a toxic chemical.…”

“…Based on a review of mathematical models of the movement of gas mixtures, it was decided to use a spatial non-stationary model of a gaseous admixture dispersion in the surface layer of the atmosphere [30]. The model considers the convective transfer of mass, momentum and energy as the main factor influencing the main physical processes.…”

“…This assumption allows using the simplified Navier-Stokes equations, which are obtained by dropping the viscous terms (Euler approach with source terms). The complete system of equations describing the non-stationary three-dimensional flow of a two-component gas mixture in this formulation, boundary and initial conditions, numerical solution algorithm, and numerical method are presented in [30]. Moreover, this approach is extended to pressure disturbances of the air during the release and combustion of explosive gases [31], which makes it possible to evaluate the landscape configuration influence on accident consequences [32], assess the safe dimensions of protection devices [33], and consider in future combined scenarios of accident situations.…”

“…The toxic substance gas phase release modelling is implemented by setting the boundary conditions of 'evaporation' on the corresponding faces of the finite-difference computational cells that are adjacent to the surface of the strait spot [30]. The simulation of the cessation of evaporation from the spill spot is carried out by replacing the boundary conditions with the 'non-flow' condition [35].…”

“…In order to reach the purpose of the work to assess the influence of the wind speed on hazardous zone square, a new approach is suggested and used in this research which integrates two (gas dynamics and safety) models. The first one (mathematical model of multicomponent gas mixture movement based on Euler approach) allows extracting current time value of hazardous factor (toxic inhalation dose) taking to account influence of the wind speed, and the second one (probit analysis model) gives us an opportunity to assess the environmental consequences (human lethal probability, and hazardous zone area) to consider mitigation means [30]. In the future, this approach can allow simulating not only isolated accident scenario of toxic gas release and dispersion but consider more complicated scenarios with flammable or even explosive gas admixtures with other hazardous factors (pressure wave and heat flow).…”