******************* This email from josuelkr@gmail.com originated outside Imperial. ******************* Dear Nektar users, I am doing some tests using IncNavierStokes solver + steady driver (with default parameters) + periodic boundary conditions. I wonder if someone has to take some extra care if one of the boundaries is similar to a sawtooth wave, as an example. Specifically, I took initially a 2D-Couette flow. After that, I substituted one of the flat walls to a tilted small square step. Results seems to be nonphysical. I played with different meshes and time integration methods but could not draw any conclusion. My .xml file solver info is: <SOLVERINFO> <I PROPERTY="SolverType" VALUE="VelocityCorrectionScheme"/> <I PROPERTY="TimeIntegrationMethod" VALUE="IMEXOrder2"/> <I PROPERTY="EQTYPE" VALUE="UnsteadyNavierStokes"/> <I PROPERTY="AdvectionForm" VALUE="Convective"/> <I PROPERTY="Projection" VALUE="Galerkin"/> <I PROPERTY="Driver" VALUE="SteadyState"/> </SOLVERINFO> <EXPANSIONS> <E COMPOSITE="C[0]" NUMMODES="12" TYPE="MODIFIED" FIELDS="u,v,p" /> </EXPANSIONS> Any help would be appreciated. Thank you in advance, J PS: I can provide .xml and .geo files I am working with if necessary.