I put together a FEM solver to do some structural analysis. At the moment I am trying to add stress visualization feature to my code. The post-processing is done with Paraview and the results with which I am trying to verify my code are from the following problem:
The structure is two square plates welded on one edge together to form the figure shown in the images below. The structure is clamped at two points as shown by red circles and a uniformely distributed load is applied on the upper edge of the structure as shown below. The simulation was run once using structured mesh and second time using unstructured mesh the results using structured mesh are somehow reasonable even though not completely satisfactory but the results from unstructured mesh are absolutely off base!
At a first glimpse what could be done wrong in transition from structured mesh to unstructured mesh (from coding point of view) that results in such discrepancy?