Excellent. With regards Abhishek On Mon, 21 Nov 2022 at 4:58 pm, <nandan.sarkar@iitkgp.ac.in> wrote:

Dear Sir,

Thanks for the correction. The code is working now.

Regards

Nandan Sarkar

*From:* Abhishek Kumar <abhishek.kir@gmail.com> *Sent:* Monday, November 21, 2022 1:16 AM *To:* nandan.sarkar@iitkgp.ac.in *Cc:* nektar-users@imperial.ac.uk *Subject:* Re: [Nektar-users] Floquet stability analysis

Dear Nandan,

I can see that there is an issue with your expansion definition. You are missing the field "w". The correct expansion is as follows:

*<EXPANSIONS>*

*<E *COMPOSITE*=*"C[0]" NUMMODES*=*"7" TYPE*=*"GLL_LAGRANGE_SEM" FIELDS*=*"u,v,w,p"* />*

*</EXPANSIONS>*

Also, remember to put "period" in the parameters. I have attached the XML file, which I used to reproduce Barkley and Henderson, JFM, 1996.

With regards

Abhishek

---------------------------------------------------------------------------------------

Abhishek Kumar

Assistant Professor (Research)

Centre for Fluid and Complex Systems

Coventry University, Coventry CV15FB

Web: https://sites.google.com/view/abhishekkir

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On Fri, Nov 18, 2022 at 9:55 AM <nandan.sarkar@iitkgp.ac.in> wrote:

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Dear all,

I am trying to perform a Floquet stability analysis using Nektar++ but facing some errors. I have generated a two-dimensional periodic base flow of flow past a cylinder, at slices, and using the same in an XML file for stability analysis. Below are the output and some relevant sections of the XML file. It would be of great help to fix the issue or point to some already set-up example cases for the Floquet stability analysis.

#IncNavierStokesSolver Cylinder_Floquet.xml

read base flow file Cylinder-Base_0.chk

read base flow file Cylinder-Base_1.chk

read base flow file Cylinder-Base_2.chk

read base flow file Cylinder-Base_3.chk

read base flow file Cylinder-Base_4.chk

read base flow file Cylinder-Base_5.chk

read base flow file Cylinder-Base_6.chk

read base flow file Cylinder-Base_7.chk

read base flow file Cylinder-Base_8.chk

read base flow file Cylinder-Base_9.chk

baseflow info : interpolation order 0, period 0.00111111, periodicity yes

baseflow info : files from 0 to 9 (skip 1) with 10 time intervals

Fatal : Level 0 assertion violation

Expect to have three velocity fields with homogenous expansion

XML file snippet:

<SOLVERINFO>

<I PROPERTY="SOLVERTYPE" VALUE="VelocityCorrectionScheme"/>

<I PROPERTY="EQTYPE" VALUE="UnsteadyNavierStokes" />

<I PROPERTY="EvolutionOperator" VALUE="Direct" />

<I PROPERTY="Projection" VALUE="Galerkin" />

<I PROPERTY="TimeIntegrationMethod" VALUE="IMEXOrder2" />

<I PROPERTY="ModeType" VALUE="HalfMode" />

<I PROPERTY="Driver" VALUE="ModifiedArnoldi" />

<I PROPERTY="Homogeneous" VALUE="1D" />

</SOLVERINFO>

<PARAMETERS>

<P> TimeStep = 0.001 </P>

<P> NumSteps = 1000 </P>

<P> IO_CheckSteps = 100 </P>

<P> IO_InfoSteps = 100 </P>

<P> Re = 188 </P>

<P> Kinvis = 1./Re </P>

<P> kdim = 4 </P>

<P> nvec = 2 </P>

<P> evtol = 1e-6 </P>

<P> N_slices = 10 </P>

<P> LZ = 2.4166 </P>

</PARAMETERS>

<EXPANSIONS>

<E COMPOSITE="C[0]" NUMMODES="7" FIELDS="u,v,p" TYPE="GLL_LAGRANGE" />

</EXPANSIONS>

Thank you in advance.

Regards,

Nandan Sarkar

PhD candidate

Dept. of Mechanical Engineering

Indian Institute of Technology Kharagpur

India 721302

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