A flame propagation model on a network with application to a blocking problem

We consider the Cauchy problem $$\partial_t u+H(x,Du)=0 \quad (x,t)\in\Gamma\times (0,T),\quad u(x,0)=u_0(x) \quad x\in\Gamma$$ where $\Gamma$ is a network and $H$ is a convex and positive homogeneous Hamiltonian which may change from edge to edge. In the former part of the paper, we prove that the Hopf-Lax type formula gives the (unique) viscosity solution of the problem. In the latter part of the paper we study a flame propagation model in a network and an optimal strategy to block a fire breaking up in some part of a pipeline; some numerical simulations are provided.