From: nektar-users-bounces@imperial.ac.ukOn Behalf OfStanisław Gepner

Sent: January 29, 2019 2:38:37 PM (UTC-05:00) Eastern Time (US & Canada)
To: nektar-users@imperial.ac.uk
Subject: Re: [Nektar-users] FW: Restarting a 3D1D case with a 2D converged case

Hi Amitvikram,

Here is an example of initializing with a mix of conditions.

      <FUNCTION NAME="InitialConditions">
        <E VAR="u" VALUE="0" />
        <E VAR="v" VALUE="0" />
        <F VAR="w" FILE="geom_2D.fld" />
        <E VAR="p" VALUE="0" />
      </FUNCTION>

Best,

Stan Gepner

On 1/29/19 8:21 PM, Stanisław Gepner wrote:

Hi Amitvikram,

Not in the chk file but in the XML session definition file. You should have the initial conditions node. Inside you initialize u, v, p from the file and, in a separate statement w, to whatever you want, value or function.

Pozdrawiam,
Stanisław Gepner

29 sty 2019 20:12 Amitvikram Dutta <amitvdutta23@gmail.com> napisał(a):

Hi Stanislaw,

How do you initialise 'w' in the 2D restart .chk file?

Sincerely,

On Tue, Jan 29, 2019 at 1:41 PM Amitvikram Dutta <amitvikram.dutta@uwaterloo.ca> wrote:

 

---

From: nektar-users-bounces@imperial.ac.ukOn Behalf OfStanisław Gepner
Sent: January 29, 2019 1:40:52 PM (UTC-05:00) Eastern Time (US & Canada)
To: Amitvikram Dutta
Cc: nektar-users
Subject: Re: [Nektar-users] Restarting a 3D1D case with a 2D converged case

Hi,

I do it all the time, so there should not be any fundamental problems with using a 2d solution to start the homogeneous expansion case.

Just make sure you initialize all variables, some with the chk file and some manually.

Pozdrawiam,
Stanisław Gepner

29 sty 2019 19:10 Amitvikram Dutta <amitvdutta23@gmail.com> napisał(a):

Hi all,

I'm studying 3D devlopement of jets and am using a 3D1D setup with Fourier coefficients in the spanwise directions. Instead of starting a 3D1D case from scratch (the mesh contains 32 million DOF in 3D) I was thinking of trying out a few strategies in order to speed up convergence.

I have tried out the steady-state module but it seems to take a rather long time to converge as well.

I was thinking therefore, whether it would be possible to start the case in 2D, and once it reaches convergence, to switch over to a 3D 1D mode using a 2D .chk file as a restart point.

I have tried out a few cases with the procedure described above, but cases always seem to blow up after restarting in the 3D 1D mode. I could explore the parameter space by reducing the time-step or number of expansion modes etc, but I'd like to know if there is a fundamental block to this kind of approach, or indeed if there are better approaches to speeding up convergence.

Sincerely,

--

Amitvikram Dutta

Graduate Research Assistant

Fluid Mechanics Research Lab

Multi-Physics Interaction Lab

University of Waterloo

29 sty 2019 19:10 Amitvikram Dutta <amitvdutta23@gmail.com> napisał(a):

Hi all,

I'm studying 3D devlopement of jets and am using a 3D1D setup with Fourier coefficients in the spanwise directions. Instead of starting a 3D1D case from scratch (the mesh contains 32 million DOF in 3D) I was thinking of trying out a few strategies in order to speed up convergence.

I have tried out the steady-state module but it seems to take a rather long time to converge as well.

I was thinking therefore, whether it would be possible to start the case in 2D, and once it reaches convergence, to switch over to a 3D 1D mode using a 2D .chk file as a restart point.

I have tried out a few cases with the procedure described above, but cases always seem to blow up after restarting in the 3D 1D mode. I could explore the parameter space by reducing the time-step or number of expansion modes etc, but I'd like to know if there is a fundamental block to this kind of approach, or indeed if there are better approaches to speeding up convergence.

Sincerely,

--

Amitvikram Dutta

Graduate Research Assistant

Fluid Mechanics Research Lab

Multi-Physics Interaction Lab

University of Waterloo

--

Amitvikram Dutta

Graduate Research Assistant

Fluid Mechanics Research Lab

Multi-Physics Interaction Lab

University of Waterloo

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