Hi Chunhui, thanks for the email. You can try to see how the boundary conditions are imposed in the attached test file of the CompressibleSolver. In this way you should be able to setup different pressure condition at the inlet and the outlet of your domain. Thanks Daniele

On 4 Jun 2018, at 22:49, Chunhui Liu <chunhui.liu@uwaterloo.ca> wrote:

Hi everyone, I am trying to use nektar++ for a simulation of convergence and divergence nozzle. https://www.grc.nasa.gov/www/wind/valid/cdv/cdv01/cdv01.html <https://www.grc.nasa.gov/www/wind/valid/cdv/cdv01/cdv01.html> subsonic inlet and outlet case. From test case, my outlet bc was set as pressure out flow, followed the user guide. However my simulation always diverged. I don't know the reason. Is there anyone familar with boundary condition in nektar for a nozzle simulation?

In addition, I noticed that in the source code CompressibleFlowSolver there are quite a lot boundary condition. However I don't know the syntax to write these boundary condition in .xml file. Thanks!

<CONDITIONS> <PARAMETERS> <P> TimeStep = 0.00001 </P> <P> NumSteps = 10 </P> <P> FinTime = TimeStep*NumSteps </P> <P> IO_CheckSteps = 1 </P> <P> IO_InfoSteps = 1 </P> <P> GasConstant = 287.058 </P> <P> Gamma = 1.4 </P> <P> pInf = 0.9617 </P> <P> rhoInf =0.000034471 </P> <P> uInf =46.77 </P> <P> vInf = 0.0 </P> </PARAMETERS>

<SOLVERINFO> <I PROPERTY="EQType" VALUE="EulerCFE" /> <I PROPERTY="Projection" VALUE="DisContinuous" /> <I PROPERTY="AdvectionType" VALUE="FRHU" /> <I PROPERTY="TimeIntegrationMethod" VALUE="ClassicalRungeKutta4"/> <I PROPERTY="UpwindType" VALUE="HLLC" /> <I PROPERTY="ProblemType" VALUE="General" /> </SOLVERINFO>

<BOUNDARYREGIONS> <B ID="0"> C[2] </B> <!-- inlet --> <B ID="1"> C[3] </B> <!-- outlet --> <B ID="2"> C[4] </B> <!-- wall --> </BOUNDARYREGIONS>

<BOUNDARYCONDITIONS> <REGION REF="0"> <!-- inlet --> <D VAR="rho" VALUE="rhoInf" /> <D VAR="rhou" VALUE="rhoInf * uInf" /> <D VAR="rhov" VALUE="rhoInf * vInf" /> <D VAR="E" VALUE="pInf / (Gamma - 1) + 0.5 * rhoInf * (uInf * uInf + vInf * vInf)"/> </REGION> <REGION REF="1"> <!--outlet--> <D VAR="rho" USERDEFINEDTYPE="PressureOutflow" VALUE="0" /> <D VAR="rhou" USERDEFINEDTYPE="PressureOutflow" VALUE="0" /> <D VAR="rhov" USERDEFINEDTYPE="PressureOutflow" VALUE="0" /> <D VAR="E" USERDEFINEDTYPE="PressureOutflow" VALUE="0" /> </REGION>

Chunhui Liu Mechanical and Mechatronics Engineering University of Waterloo _______________________________________________ Nektar-users mailing list Nektar-users@imperial.ac.uk <mailto:Nektar-users@imperial.ac.uk> https://mailman.ic.ac.uk/mailman/listinfo/nektar-users <https://mailman.ic.ac.uk/mailman/listinfo/nektar-users>