Surface fire spread model based on lumped parameter approach / Modelo de propagação de fogo em incêndios de superfície baseado no método nodal

AUTOR(ES)

Rodolfo Maduro Almeida

DATA DE PUBLICAÇÃO

2007

RESUMO

This work presents a new approach for a surface re spread model applicable to wildland re modelling. The mathematical method used in the modeling is the lumped parameter approach. In this method the thermal domain is divided in a nite number of volumes, supposed isothermal and with homogeneous properties, called nodes. To each node are attributed a temperature, a thermal capacitance and possibly internal heat generation. Each node exchanges heat with its neighbors through conductive condutances and interacts with the ames and the ambient through radiatives conductances. When the node reach the temperature of ignition, it is subject to an internal heat generation that keeps on until total consumption of the vegetal fuel. The ame over each node within the reaction zone is approximated by a parallelopiped whose surfaces emits radiation to the nodes positioned in its surrounding. Each ame has a predetermined temperature-time prole model, geometrical properties and a residence time that depend of ambient condictions. The system of dierential equations, representing the net heat balance of the nodes, is numerically solved, yielding, among other results, the temporal evolution of the ame on the surface. The conductance matrix, as well as the thermal capacitances and the internal heat generation, is updated each time step. The in uence of the nodal division on the re spread rate and on the computational cost is analyzed. Simulation are carried out varying the wind speed and the fuel load. It is observed that the rate of spread is directly related with the geometric properties of the ame nodes. The model shows to be exible in situations involving propagation in surfaces with obstacles. The results are encouraging for the use of the lumped parameter approach in the the surface re spread modelling.

ASSUNTO(S)

computação aplicada modelos matemáticos lumped parameter systems mathematical models incêndios florestais forest fires método nodal

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