Hi Spencer.
Thanks for replying I wish you a great day, could you check this is my settings and I will be very grateful if Andera can send me his file at 3900 to check the settings. but also what about using a different time integration method "BDFImplicitOrder2" instead of using "IMEXOrder2" in "TimeIntegrationMethod" , I think the two of them are 2nd order but using Implicit instead of Implicit explicit will not crash, also I will keep CFL under 1 to be sure it is fine, I tried "SpectralVanishingViscosity" it is working but it is filtering my field when I checked the velocity spectrum it was filtered. Also another case , please check my attachment file it has the same settings even with lower Reynolds at 400 using velocity ratio is crashing, for outlet BC i am already using HOutflowa.
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<?xml version="1.0" encoding="UTF-8" ?>
<NEKTAR>
<EXPANSIONS>
<E COMPOSITE="C[1]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> <!-- 1 Domain inlet plate upper -->
<E COMPOSITE="C[2]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> <!-- 2 Domain inlet plate lower -->
<E COMPOSITE="C[3]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> <!-- ****3 Domain square faces up down front meshs**** -->
<E COMPOSITE="C[4]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> <!-- 4 Domain upper domain lower in up stream -->
<E COMPOSITE="C[5]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> <!-- 5 Domain upper lower downstream -->
<E COMPOSITE="C[6]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> <!-- ***6 Domain down stream back side square*** -->
<E COMPOSITE="C[7]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> <!-- 7 Domain down stream after square big one -->
<E COMPOSITE="C[8]" NUMMODES="3" FIELDS="u,v,w,p" TYPE="MODIFIED" /> <!-- 7 Domain down stream after square big one -->
</EXPANSIONS>
<CONDITIONS>
<SOLVERINFO>
<I PROPERTY="SOLVERTYPE" VALUE="VelocityCorrectionScheme"/>
<I PROPERTY="EQTYPE" VALUE="UnsteadyNavierStokes" />
<I PROPERTY="Projection" VALUE="Continuous" />
<I PROPERTY="EvolutionOperator" VALUE="Nonlinear" />
<I PROPERTY="TimeIntegrationMethod" VALUE="IMEXOrder2" />
<I PROPERTY="Driver" VALUE="Standard" />
<I PROPERTY="HOMOGENEOUS" VALUE="1D" />
<I PROPERTY="AdvectionForm" VALUE="SkewSymmetric" />
<I PROPERTY="Extrapolation" VALUE="Standard" />
<I PROPERTY="USEFFT" VALUE="FFTW" /> <!-- <I PROPERTY="DEALIASING" VALUE="ON" /> -->
<I PROPERTY="SPECTRALHPDEALIASING" VALUE="ON" /> <!-- <I PROPERTY="SpectralVanishingViscosity" VALUE="True" /> -->
</SOLVERINFO>
<PARAMETERS>
<P> TimeStep = 0.0003 </P>
<P> NumSteps = 550000 </P> <!-- 60sec -->
<P> IO_CheckSteps = 5000 </P> <!-- 120 check files--> 520
<P> IO_InfoSteps = 10 </P>
<P> Re = 2000 </P>
<P> Kinvis = 1./Re </P>
<P> IO_CFLSteps = 50 </P>
<P> LZ = 10 </P> <!-- 3. * Fastest spanwise -->
<P> HomModesZ = 16 </P> <!-- how many cells for Z direction -->
</PARAMETERS>
<VARIABLES>
<V ID="0"> u </V>
<V ID="1"> v </V>
<V ID="2"> w </V>
<V ID="3"> p </V>
</VARIABLES>
<BOUNDARYREGIONS>
<B ID="0"> C[9] </B> <!-- Inlet1_upper -->
<B ID="1"> C[10] </B> <!-- Inlet2_Lower -->
<B ID="2"> C[11] </B> <!-- Splitter plate -->
<B ID="3"> C[12] </B> <!-- Upper Boundary -->
<B ID="4"> C[13] </B> <!-- Lower_Boundary -->
<B ID="5"> C[14] </B> <!-- Outlet -->
<B ID="6"> C[15] </B> <!-- Wall_square -->
</BOUNDARYREGIONS>
<BOUNDARYCONDITIONS>
<REGION REF="0"> <!-- Inlet_upper -->
<D VAR="u" VALUE="1" />
<D VAR="v" VALUE="0" />
<D VAR="w" VALUE="0" />
<N VAR="p" USERDEFINEDTYPE="H" VALUE="0"/>
</REGION>
<REGION REF="1"> <!-- Inlet_lower -->
<D VAR="u" VALUE="1" />
<D VAR="v" VALUE="0" />
<D VAR="w" VALUE="0" />
<N VAR="p" USERDEFINEDTYPE="H" VALUE="0"/>
</REGION>
<REGION REF="2"> <!--Splitter plate -->
<D VAR="u" VALUE="0" />
<D VAR="v" VALUE="0" />
<D VAR="w" VALUE="0" />
<N VAR="p" USERDEFINEDTYPE="H" VALUE="0" />
</REGION>
<REGION REF="3"> <!-- Upper Boundary -->
<N VAR="u" USERDEFINEDTYPE="H" VALUE="0" />
<D VAR="v" VALUE="0" />
<N VAR="w" USERDEFINEDTYPE="H" VALUE="0" />
<N VAR="p" USERDEFINEDTYPE="H" VALUE="0" />
</REGION>
<REGION REF="4"> <!-- Lower_Boundary -->
<N VAR="u" USERDEFINEDTYPE="H" VALUE="0" />
<D VAR="v" VALUE="0" />
<N VAR="w" USERDEFINEDTYPE="H" VALUE="0" />
<N VAR="p" USERDEFINEDTYPE="H" VALUE="0" />
</REGION>
<REGION REF="5"> <!-- Outlet -->
<N VAR="u" USERDEFINEDTYPE="HOutflow" VALUE="0" />
<N VAR="v" USERDEFINEDTYPE="HOutflow" VALUE="0" />
<N VAR="w" USERDEFINEDTYPE="HOutflow" VALUE="0" />
<D VAR="p" USERDEFINEDTYPE="HOutflow" VALUE="0" /> </REGION>
<REGION REF="6"> <!-- WallA_square -->
<D VAR="u" VALUE="0" />
<D VAR="v" VALUE="0" />
<D VAR="w" VALUE="0" />
<N VAR="p" USERDEFINEDTYPE="H" VALUE="0" />
</REGION>
</BOUNDARYCONDITIONS>
<!-- We initialise from pre-computed flow for speed -->
<FUNCTION NAME="InitialConditions">
<E VAR="w" VALUE="awgn(1e-3)*cos(2*PI*z/LZ)" /> -->
<!-- <F VAR="u,v,w,p" FILE="Start.chk" /> -->
<!-- <E VAR="u,v,w,p" VALUE="0" /> -->
<F VAR="u,v,p" FILE="Start2D.chk" /> <!-- start from 2D results -->
</FUNCTION>
<FUNCTION NAME="ExactSolution">
<E VAR="u" VALUE="0" />
<E VAR="v" VALUE="0" />
<E VAR="w" VALUE="0" />
<E VAR="p" VALUE="0" />
</FUNCTION>
</CONDITIONS>
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Thanks,
Regards