Abstract

Computational modeling (CFD) has made great strides in the last 20 years in fighting and overcoming its "expensive" stigma. The oil & gas industry has embraced the use of CFD to assess everything from the design of equipment, optimization of process flows, and hazards modeling of fire and explosion events all in an effort to strive for the goal of inherently safer designs. In current offshore facility design, CFD modeling, to assess the consequences of vapor cloud explosions has been established as common practice.

For most major projects, CFD explosion modeling is used heavily in Feed and Detailed (later) stages of design. At these stages hundreds of scenarios are simulated and combined with extensive probabilistic and statistical calculations to define design loads of critical systems and assess risk. The primary advantage of using CFD is that it incorporates more details of the design and provides more realistic and design specific analysis. In the case of explosions, CFD provides valuable data for design, particularly explosion data that is significantly more accurate than that from simple open field models.

Despite this adoption within the design process and decades of advances, CFD modeling practitioners still admit that there are increases of cost and time, when compared to the ever-present phenomenological approaches. This has kept many design processes from utilizing CFD in the earliest stages; namely Concept and pre-Feed. The arguments have traditionally been along the lines of:

  • The design is progressing and changing too fast to allow time for CFD models to be built.,

  • There is insufficient model detail to construct viable CFD models.,

  • The early stage concerns can be captured "well enough" with simple approaches., etc.

Modeling representations and approaches can be simplified and streamlined, while still providing the advantages of CFD. Variability in geometric representations can be captured with physics representations rather than needing to create predictive CAD geometry. These types of simplifications can increase the ability to simply change and update models and conduct early stage sensitivities in projects, while still capturing critical explosion effects.

The purpose of this paper will be to show how these simplified approaches can be used in an effective and efficient manner in early stages of design. That the traditional arguments against early adoption of CFD can be countered, with the end result being greater early stage information and influence on the design. Allowing effective change at a time in the process when it is not cost prohibitive and other controls have yet to prohibit design changes. The result being a continued improvement in the goal of inherently safer design.

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