My FEM scheme uses a 4-node quadrilateral element with bilinear shape functions. The simple problem I'm solving is. $\nabla ^2 f = 5$ But as I increase the number of nodes, the plot of the solution becomes flatter. I'm stumped as to why this might happen.Two plots below show how when I change the size of the mesh from a 7x7 to a approx. 30x30, the plot becomes much more spread out. Also the boundary condition is that $f = 0$ on the boundary
FIXED, had some typos in my code