From: Sahai, Amal <sahai2@il...>  20140708 08:09:44

I was a little unsure of the following bit of code in Example 2 for the System of Equations (the Incompressible Unsteady Navier Stokes Solver). const bool pin_pressure = true; if (pin_pressure) { const unsigned int pressure_node = 0; const Real p_value = 0.0; for (unsigned int c=0; c<elem>n_nodes(); c++) if (elem>node(c) == pressure_node) { Kpp(c,c) += penalty; Fp(c) += penalty*p_value; } } } // end boundary condition section Why exactly is "elem>node(c) == pressure_node" condition being used? I would imagine that pressure at all points on the surface where Dirichlet Boundary condition is being imposed would be made zero. In that case why are nodes with the global id number 0 being considered? Also, since Pressure is a First order approximation, how does LibMesh decide on which nodes (in a given element) would be used be for storing Pressure values. Regards Amal Regards Amal 