Mesh deformation creates crazy mesh
 

I have a 2D airfoil mesh. It solves great, but I want it to be used for small changes in the airfoil shape. I have used SU2_DEF to deform the mesh. I am using the DV_KIND=AIRFOIL that asks for an airfoil file. I put in the parameters but the mesh_out.su2 is all crazy and of course fails when trying to solve. How robust is the mesh deformation for airfoils? Are there any specific settings that I need to set or things I need to watch out for?

Sorry for the delay in reply.
The first thing to check is the surface deformation - open the surface_grid.dat file and check that the change in the airfoil shape is logical. If not, you may need to check options like DV_MARKER.

If that checks out, the deformation settings are the next place to go: for an evenly-spaced mesh CONSTANT_STIFFNESS often works well, but for a viscous mesh you may want to try the INVERSE_VOLUME or WALL_DISTANCE settings. Start with the default number of deformation iterations. (They will be used if you comment out those options)