[Nektar-users] boundary condintion file for CompressibleFlowSolver in neakar

4 Jun 2018

      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>
    <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