Multiphysics simulations of fire inside the cavity of a facade

Abstract

The facade system is highly complex and requires achieving multiple objectives to provide occupants with a safe and comfortable environment. Any attempt to improve these objectives, such as aesthetic, thermal or acoustic insulation, could potentially affect the fire safety of the facade system. This is especially true as novel materials were introduced over the last decades, resulting in an ongoing rise in facade fires. Researchers have observed that a narrow cavity in a facade system encourages rapid facade fire spread. Unfortunately, there is little knowledge of quantifying the impact of cavities on a facade fire. Computational Fluid Dynamics (CFD) fire simulation represents an excellent tool to complement experimental studies on fire inside a narrow cavity of a flammable facade. Cavity fire is a multiphysics phenomenon, and all physics, i.e. fluid flow, heat transfer, buoyancy, combustion and pyrolysis involved in the model must be coupled step-by-step for a narrow cavity fire scenario to ensure model reliability. This thesis provides a step-by-step development of a CFD simulation for a narrow cavity fire. We split the facade cavity fire into six different scenarios with increasing complexity and validated the model against experimental data in the literature to limit the compensation effect. The compensation effect is the concept where similar results could be obtained by varying two or more parameters. We studied how cavity barriers affect fire dynamics and performed parametric studies to quantify the impact of both material properties and cavity width on fire dynamics inside a cavity of a flammable facade. This work demonstrates that modelling represents a powerful tool to aid in understanding facade cavity fire to improve building fire safety.