Coupling of numerical models of mesh generation and heat transfer of a tree trunk in a forest fire environment

Abstract

This work presents a coupling between two numerical models, one for mesh generation and the other for heat transfer analysis, used to characterize the tree trunk thermal behaviour located in a forest fire environment. The geometry of the tree trunk is developed, using adaptive mesh generation, to evaluate the view factors, used to calculate the heat exchanges by radiation, between the virtual trunk tree and a fire front. The fire front represents the existing forest fire. The trunk tree thermal behavior numerical model is based on energy equations. The energy balance integral and differential equations consider the heat exchange by conduction inside the trunk tree, the heat exchange by convection between the trunk tree external surfaces and the environment and the heat exchanges by radiation between the trunk tree external surfaces and the environment and fire front. The numerical simulation is characterized by the propagation of a fire front at a constant fire spread rate of 0.01 m/s from a distance of 5 m upstream of the tree trunk. With an irregular shape, the tree trunk has a height of 2 m and an external diameter of 0.2 m. The fire front has a tilt angle of 45º, 10 m wide and 2 m high. The temperature distribution in the tree trunk was obtained for a wind speed of 0.1 m/s, an average flame temperature of 500ºC, an environmental air temperature of 20ºC and an air relative humidity around the trunk tree of 50%. The temperature distribution obtained allows to identify the areas of the tree trunk tissues that were most affected by the passage of fire.

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