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 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>
<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