Grid Generation and Heat Transfer in a Complex Topology Maritime Pine Tree in Forest Fire Environments

Abstract

This article presents a study on the grid generation and heat transfer in a complex topology maritime pine tree in a forest fire environment. The numerical model of the maritime pine tree thermal behaviour is developed and applied. This numerical model is based on energy balance integral equations for the maritime pine tree elements. These equations are obtained for the heat exchanges by conduction within the maritime pine tree elements, by convection between the external maritime pine tree surfaces and the environment, and by radiation between the external maritime pine tree surfaces and the fire front. The geometry of the virtual maritime pine maritime pine tree was here developed applying mesh generation, which is used to evaluate the view factors. In turn, these view factors are used to calculate the heat exchanges by radiation between the virtual maritime pine tree and the fire front. The virtual maritime pine tree geometry is constituted by 8863 cylindrical elements, which represent their trunks, branches and leaves, and it is divided into four levels. The input data considered in the numerical simulation are the mean flame temperature of 500ºC, the air temperature of 20ºC, the wind speed of 10 m/s and the air relative humidity around the pine tree of 50%. The numerical simulation results are the view factors and the evolution of the surface temperature of the maritime pine tree elements obtained in a transient regime. The values of the view factors and the surface temperature of the maritime pine tree elements decrease from the first level, near the ground, to the last level, at the top of the maritime pine tree. The stabilization time of the surface temperatures of the maritime pine tree elements decreases according to the increase of the height to which these elements are located.

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