Hi Amitvikram, so, if in Gmsh have the following physical surfaces: 2: Airfoil 3: Inlet 4: Outlet 5: TandB The corresponding quantities that will be generated in the .xml file are called COMPOSITES and are identified by C[2], C[3], C[4] and C[5]. To appropriately prescribe the BCs you need to set you BOUNDARYREGIONS as you did - i.e.: <BOUNDARYREGIONS> <B ID="0"> C[2] </B> <B ID="1"> C[3] </B> <B ID="2"> C[4] </B> <B ID="3"> C[5] </B> </BOUNDARYREGIONS> And on each of these boundary regions you need to apply the boundary conditions you want - for instance, for the airfoil you will have: <BOUNDARYCONDITIONS> <REGION REF="0"> <D VAR="u" VALUE="0" /> <D VAR="v" VALUE="0" /> <N VAR="p" USERDEFINEDTYPE="H" VALUE="0" /> </REGION> Where you can now see the REGION REF="0", refers to the boundary region that identifies COMPOSITE C[2] that is your airfoil. Hope this helps. Best wishes, Gianmarco ________________________________ From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> on behalf of Amitvikram Dutta <amitvdutta23@gmail.com> Sent: 26 April 2016 02:02 To: nektar-users Subject: [Nektar-users] Correct Designation of Boundary Conditions Hi all, I'm having some confusion in applying appropriate boundary conditions to proper named surfaces in my mesh. I'm using v4.2.0 with the original mesh being constructed in gmsh. I subsequently use the MeshConvert utility to generate the partial xml file for the simulation. In my .msh file I have my surfaces set as $PhysicalNames 5 2 1 "Unspecified" 1 2 "Airfoil" 1 3 "Inlet" 1 4 "Outlet" 1 5 "Tandb" $EndPhysicalNames I want to apply no-slip condition to the airfoil, a velocity inlet , a constant pressure outlet and no slip wall to TandB as well. My relevant section of the xml case file is given below. I'd like to know if I'm implementing the boundary conditions correctly. <BOUNDARYREGIONS> <B ID="0"> C[2] </B> <B ID="1"> C[3] </B> <B ID="2"> C[4] </B> <B ID="3"> C[5] </B> </BOUNDARYREGIONS> <BOUNDARYCONDITIONS> <REGION REF="0"> <D VAR="u" VALUE="0" /> <D VAR="v" VALUE="0" /> <N VAR="p" USERDEFINEDTYPE="H" VALUE="0" /> </REGION> <REGION REF="1"> <D VAR="u" VALUE="1" /> <D VAR="v" VALUE="0" /> <N VAR="p" USERDEFINEDTYPE="H" VALUE="0" /> </REGION> <REGION REF="2"> <N VAR="u" VALUE="0" /> <N VAR="v" VALUE="0" /> <D VAR="p" VALUE="0" /> </REGION> <REGION REF="3"> <D VAR="u" VALUE="0" /> <D VAR="v" VALUE="0" /> <N VAR="p" USERDEFINEDTYPE="H" VALUE="0" /> </REGION> </BOUNDARYCONDITIONS> <FUNCTION NAME="InitialConditions"> <E VAR="u" VALUE="1" /> <E VAR="v" VALUE="0" /> <E VAR="p" VALUE="0" /> </FUNCTION> -- Amitvikram Dutta MASc Candidate Graduate Research Assistant Okanagan CFD Laboratory University of British Columbia | Okanagan Campus