1.1 Mesh generation

The first step is to generate a mesh that is readable by Nektar++ . The files necessary in this section can be found in $/NEKTUTORIAL/Channel/Geometry/. To achieve this task we use Gmsh in conjunction with the Nektar++ pre-processing utility called $NEK/MeshConvert. Specifically, we first generate the mesh in figure 1 using Gmsh and successively we convert it into a suitable Nektar++ format using $NEK/MeshConvert.

Task 1.1 Convert the Gmsh geometry provided into the XML Nektar++ format and with two periodic boundaries

Examine the Channel.xml and Channel-al.xml files you have just created. Only the mesh and default expansions are defined at present and the only difference between the two files is the ordering of the edges in the section composite ID=3 which has been re-ordered in order to apply periodic boundary conditions correctly.

Warning: There is currently an issue when using the coupled solver and periodic edges which is being investigated. For achieving the correct channel flow stability results when using the Coupled Linearised Navier-Stokes algorithm (see section 1.3.2), please use the files provided in the folder $NEKTUTORIAL/Channel/Stability/Coupled.