# GoZone: A Numerical Model for Travelling Fires Based on Cellular Automata Concept
###### Abstract
In an unpublished internal report \"Fire Models for Large Firecells\" [16], [PERSON] proposed an approach in which he applied specific fire models to develop temperature-time relationships specifically for travelling fires: the _Large Firecell Method_. Although this pioneering model introduced aspects that are not considered in the conventional uniform burning assumption, it was not widely used in civil engineering, possibly because of insufficient experimental validation [17]. In 2007, [PERSON] et al. proposed an alternative methodology for fuel controlled travelling fire, derived from a series of computational fluid dynamics (CFD) analyses in conjunction with engineering simplifications [18]. The main feature of the model is the proposal of a near field (fire plume) and a far field (hot smoke layer). This model was further developed by [PERSON] and put forward as a design methodology [6]. For the near field, a uniform conservative temperature of 1200 \({}^{\circ}\)C was initially assumed. Afterward, [PERSON] further improved [PERSON]'s model by taking into account more localised fire dynamics, considering realistic fire spread rates, which, as a consequence, reduced the range of possible fire sizes that must be considered [19]. Within this framework, the user must parametrically assess a range of various fire sizes, irrespective of the compartment ventilation, under the assumption of a rectangular compartment with a 1D travelling direction at a constant spread rate. Subsequently, a new model was developed and implemented by [PERSON] et al. [20]. This model was based on [PERSON]'s localised fire model for the near field and a zone model for the far field. The temperature was evaluated step by step and considers the smoke layer evolution and its accumulation during the fire. In this model, the fire model is also based on a predetermined one-dimensional fire path (typically, the fire is \"circling\" around a central core in a rectangular floor plan area). In [PERSON]'s model, the proposed models to assess travelling fires are only suitable for specific geometrical configurations, often limited to rectangular compartments. The fire is imposed to \"travel\" through the compartment with a velocity that is constant in each analysis and a fire path that is predefined. The practical range of application results are limited. Moreover, experimental evidence has been found on the possibility of a travelling fire under a ventilated condition [21]. This underlines the necessity to overcome the oversimplified assumption adopted in the first travelling fire models where the fire is assumed to be fuel controlled [22]. The aim of this paper is to present a numerical model that combines the concept of zone model with one of cellular automata. The software GoZone in which the model has been implemented is intended to be a practical solution to analyse fires in large compartments of any shape (see Appendix A). It aims to describe the essential features of the fire dynamics from ignition to a phase of localised fire that may travel in the compartment, possibly followed by a flashover, with a specific strategy to take into account under ventilated fire conditions.