I want to solve the 2D poisson problem using the interior penalty discontinuous galerkin methods (IPDG methods) :

−∇a(x)(∇u)=0 in Ω.

The variational formulation is such that : $a_{\epsilon}(u,v)=\sum_{K\in T_h}\int_K a\nabla u\cdot \nabla v-\sum_{e\in \Gamma_h\cup \Gamma_D}\int_e\{a\nabla u\cdot n_e\}[v]+ \sum_{e\in \Gamma_h\cup \Gamma_D}\int_e\epsilon\{a\nabla v\cdot n_e\}[u] + \sum_{e\in \Gamma_h\cup \Gamma_D}\frac{\sigma_0}{|e|}\int_e[u][v]$

I managed to get the implementation right and to compute and assemble the flux terms for a quadrilateral element. Yet for the triangles, it gets a little bit hard and I dont know how to do it. Can someone help me please ?

Thank you