The consequence analysis is used to define the extent and nature of effects caused by undesired events being of great help when quantifying the damage caused by such events. For the case of leaking of flammable and/or toxic materials, effects are analyzed for explosions, fires and toxicity. Specific models are used to analyze the spills or jets of gas or liquids, gas dispersions, explosions and fires. The central step in the analysis of consequences in such cases is to determine the concentration of the vapor cloud of hazardous substances released into the atmosphere, in space and time. With the computational advances, CFD tools are being used to simulate short and medium scale gas dispersion events, especially in scenarios where there is a complex geometry. However, the accuracy of the simulation strongly depends on diverse simulation parameters, being of particular importance the grid resolution. This study investigates the effects of the computational grid size on the prediction of a cloud dispersion considering both the accuracy and the computational cost.Experimental data is compared with the predicted values obtained by means of CFD simulation, exploring and discussing the influence of the grid size on cloud concentration the predicted values.This study contributes to optimize CFD simulation settings concerning grid definition when applied to analyses of consequences in environments with complex geometry. INTRODUCTIONAs a result of the industrial and technological development, the presence of flammable and toxic substances has significantly increased in a number of activities. While flammable substances are used as energy sources, toxic substances are used in a huge number of industrial processes, and frequently the flammable and toxic substances are present in the same process. Activities related to the supply chain of oil and its derivatives is a current example; these substances are present in the activities of offshore and onshore production plants, in the storage and transport process and in the process of delivery to the final consumer.Although these substances are essential nowadays, there are risks involved in their manipulation, storage and transportation that should be controlled whenever possible. The consequence analysis is used to define the extent and nature of effects caused by undesired events on individuals, buildings, equipment and on the environment. For the case of leaking flammable and/or toxic materials, consequences are analyzed for explosions, fires and toxicity.The central step in this type of analysis is to determine the concentration of the vapor cloud of hazardous substances released into the atmosphere, in space and time. On the basis of this approach, the use of numerical methods associated with different algorithms of computational fluid dynamics (CFD) to
In order to quantify the damage caused by undesired events involving leakages of flammable materials, specific models are used to analyze the spills or jets of gas and liquid, gas dispersion, explosions and fires. The main step of this analysis is to estimate the concentration, in space and time, of the vapor cloud of hazardous substances released into the atmosphere; the purpose is to determine the area where a fire or explosion might occur and the quantity of flammable material in that area. Recently with the computational advances, CFD tools are used to short and medium range gas dispersion scenarios, especially in scenarios where there is a complex geometry. However, the accuracy of the simulating strongly depends on the boundary conditions. Therefore, this study investigates the sensitivity degree of the prediction of cloud dispersion to changes in values of wind speed, ambient temperature, atmospheric pressure and ground roughness. This paper con-tributes to an appropriate assessment of the effects of these environment conditions to perform an accurate dispersion simulation using CFD tools and therefore contributes to a more effective analysis of the consequences. REFERENCES INTRODUCTIONSpecific models are used to evaluate the release and dispersion of flammable substances when an undesired event occurs; the determination of the dispersion features is essential to model the consequences such as fires and explosions. The consequence analysis is used to define the extent and nature of effects caused by such events and thus is of great help when quantifying the damage caused. Dispersion models estimate the evolution and the features of the cloud, such as concentration, temperature, velocity and dimensions as a function of time and position. In the case of flammable substances, these models facilitate the prediction of an area where a fire or explosion might occur and the quantity of flammable material in that area.Nowadays, the use of numerical methods associated with different algorithms of computational fluid dynamics (CFD) to determine the concentration of the vapor cloud of hazardous substances released into the atmosphere, in space and time, has grown considerably (Comier 2008, Middha 2009, Dharmavaram, 2005. CFD is found in some commercial software tools such as CFX, FLACS and FLUENT. The CFD tools transform the governing equations of the fundamental physical principles of fluid flow in discretized algebraic forms, which are solved to find the flow field values in time and space (Anderson, 1995).CFD tools have proven promising to perform analyzes of consequences in environments with complex geometry, as in the comparative study about the use of integral and CFD tools to evaluate cloud dispersion reported by . Nevertheless, as reported by Plasmans et al. (2012), previous studies have shown that consequences analysis using CFD are frequently not easily reproduced and, in many occasions, large differences can arise between the simulation results when working with different tools and/or different C...
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