# deal.ii - ParaView "warp by scalar" of my output is not continuous

During our finite element course, we've solved the linear elasticity problem in 2D on a square (GridGenerator::hyper_cube) with $$Q_1$$ bilinear finite elements in each component. We imposed neumann homogeneous boundary conditions on one face, and homogeneous Dirichlet on the other three faces.

As outputs, we chose:

• magnitude of the solution $$u$$
• $$u_x$$ (x-displacement)
• $$u_y$$ (y-displacement)

The output of the magnitude of $$u$$ is the following:

So far so good. Now, I select $$u_x$$, and I'd like to warp it by scalar, as it is a scalar valued function. So first let's see $$u_x$$:

Now, I warp this $$u_x$$ by scalar, and the plot is the following:

i.e. it seems that the solution is flat, which is absolutely non-sense. Also, if I increase the scale factor, I got something which to me doesn't make any sense at all:

Does anyone know if this is normal, or is there something wrong in my finite element solver? If the latter, this would really surprise me

• What is the boundary condition?
– knl
Jun 28 at 18:42
• Neumann homogeneous everywhere, except on the left boundary, where is homogeneous Dirichlet. @knl Jun 28 at 18:44
• $u_x = u_y = 0$ on left? $\sigma(u)n = 0$ on others?
– knl
Jun 28 at 18:56
– knl
Jun 28 at 18:56
• Which quantity do you warp by? "Warp by scalar" just means that you choose one scalar field to provide a third dimension to the plot, but there are many quantities that one could choose: The x-displacement itself, the magnitude of the displacement, the size of cells, the distortion of cells, etc. Jun 29 at 15:52

It seems like you are using deal-ii for your simulations. Its a well established fem solver and there is a very less chance that the mistake is with the FEM solver. However, Please check the BC that you have applied to your problem ( In case, if above is not the expected solution )

Try scaling up the data using calculator filter in Paraview and then try “warp by scalar” filter on top of that to verify the plots

• I agree with you for the FEM solver part. As you can see, my BCs are fulfilled: I required neumann homogeneous everywhere, except on the left face, where I have homogeneous Dirichlet. I think the problems comes from the fact that the scalars that I was using to "warp" were the ones from the estimator, which is one output of my fem solver. Jun 28 at 20:22
• Please be clear on what you need to ask on the forum , if you find any obervations, edit the posted question immediately. Jun 29 at 20:05