# GoZone: A Numerical Model for Travelling Fires Based on Cellular Automata Concept
## 2 Overview of the Model  
The model aimed to describe the fire dynamics and its evolution in time throughout the compartment, accounting for the interactions between the fire and the compartment in terms of energy and mass balance during the course of the fire event.  
The fire dynamics and evolution in time are described by a family of models called cellular automata (CA). CA models are used to solve a wide range of problems applying the main idea proposed by [PERSON] [23] and further detailed by [PERSON] [24]. CA models have recently found applications in simulating fire spreading in forest and wildland fires [25; 26; 27]. CA models are generally characterised by:  
* A physical environment, which is made of a discrete lattice of cells of approximately equal area, called grid, in two dimensional problems. The lattice defines the domain in which CA is applied and computed. The physical environment here is the fire compartment, the floor of which is described with triangular and/or quadrilateral cells in a structured or unstructured manner. In GoZone, the discretisation can be made through a graphical user interface based on the open source mesh generator GMSH [28]. The same discretisation is mirrored up and assigned to the lower plane of the smoke layer Figure 1. The versatile character of unstructured triangular meshes makes it possible to model any shape for the plan view of the compartment, while structures of quadrilateral meshes may be used in more regular geometries such as, for example, rectangular compartments.
* The cell's states, where each cell composing the lattice has a proper state that can change in time. Change in state can be referred to a single cell or to all cells composing the lattice. The cell's state is here: burning or not. Moreover, cells are characterised with properties such as fuel load density, fire growth rate, rate of heat release density, and height of the fuel must be defined in GoZone. While the cell state can be viewed as an \"on\" or \"off\" state, a cell property is a given input of the model.
* A local transition rule, which acts upon a cell and can generate a change of state from one discrete time step to the next. The transition rule enabling a change in state of a cell from not burning to burning is described by an ignition strategy (Section 3), while a change in state of a cell to air controlled is defined here by the combustion strategy that is presented in Section 6.
* The cells' neighbourhoods. For each cell in the lattice, there is a neighbourhood that locally influences the evolution of the cell via the transition rule. The cells' neighbourhoods here are all the burning cells on the floor and the cells of the smoke layer showed that radiation to the cell is not obstructed by walls (eventual internal walls or core and, also, external walls in the compartments of non-convex shapes).  
The evaluation of energy and mass balance in the compartment is performed by the well-known 2 zone model OZone [9]. Therefore, quantities such as the time dependent thickness of the smoke layer \(Z_{s}\) and its temperature \(T_{s}\) are obtained.