Investigating the use of Geometric Shadowing and Thermal Radiation Mapping to Improve Fire Modeling in Offshore Facilities

摘要

The offshore segment of the oil & gas industry has led and continues to lead the way in the use of computational fluid dynamics (CFD) in perusing inherently safer designs. Despite this, modeling focus has remained fixed on vapor cloud dispersion and explosion modeling. Typically, during the design process hundreds of various scenarios will be simulated using CFD through the later design stages. These studies will evaluate various sizes and locations of releases and clouds, changes in ignition location, release orientation, and evaluate loads at sensitive receptors throughout a facility. Extensive probabilistic and statistical calculations will be conducted to interpolate and extrapolate these results. When it comes to fire modeling, the reliance is still with the use of simple phenomenological modeling. This is not to say that CFD fire modeling is not done, but rather when used, it is in a limited capacity with a focus on specific scenarios. These are usually the large scale, high consequence events. So, why don't we give fires the same treatment as explosions? This questions is particularly important, as facility risks are normally dominated by fire risks. The simple answer is, that fires, their behavior, and the resulting hazardous effects are more complex and sensitive to variation than compared to vapor cloud releases and explosions. In addition, fire modeling is significantly more computationally intensive, i.e. more cost and time to a project. This makes running hundreds of scenarios and developing probabilistic maps to be used for interpolation and extrapolation much more difficult. A lot of work is being done to investigate improvements to CFD fire modeling, many of which are focused on simplifying the problems we solve and the physics we represent. The biggest concern of fires, beyond direct impingement is thermal radiation. Thus, if we simplify the problem and focus on how thermal radiation is represented and calculated in fire models, we may be able to apply much more simplified modeling, while significantly increasing the quality of our solutions. The focus of this paper will be on the use of geometric shadowing calculations to improve thermal radiation representations. This paper will investigate how these techniques can be applied to offshore facilities, identify where and how they could be applied, as well as look at shortfalls in which further research is required. With the goal being to work towards bringing fire modeling to the same standard of explosion modeling without the additional cost and schedule burdens to projects of traditional CFD fire modeling.