Hi Abhishek,

Okay, that issue was pretty straightforward to solve -- advection was not being calculated for the scalar field. I have pushed that fix up to the repository, and I now get a positive eigenvalue of 2.1124 with your XML file, so pretty close to your reference value.

Thanks,

Dave

> On 7 Feb 2018, at 15:24, Abhishek Kumar <abhishek.kir@gmail.com> wrote:
>
> Dear David,
>
> Thanks for your response.
>
> I have attached the XML file for RBC stability. I am running for Ra=2000 with k=3.117. The critical value of Rayleigh number for this configuration is 1708.
>
> The growth rate for Ra=2000 of the most unstable mode should be 2.1464. However, I am getting -9.8699, a negative growth rate, which is not possible as Ra > Ra critical.
>
> With regards
> Abhishek
>
>
>
>
>
> On Wed, Feb 7, 2018 at 2:50 PM, David Moxey <D.Moxey@exeter.ac.uk> wrote:
> Hi Abhishek,
>
> Thanks for the update, glad to hear we are producing correct results on that front.
>
> Regarding the linear stability; can you share your XML file? It might just be that the base flow needs to be properly imposed in the appropriate scalar -- we probably haven't taken scalar fields into account yet in the setup.
>
> Thanks,
>
> Dave
>
> > On 6 Feb 2018, at 13:20, Abhishek Kumar <abhishek.kir@gmail.com> wrote:
> >
> > Dear David,
> >
> > Thanks for your answer. Now, I got it.
> >
> > You would be happy to know that the Rayleigh-Benard convection (RBC) solver is working properly with Nektar++. I have tested the solver and also did a benchmark with Clever & Busse JFM 1974 for the Nusselt number calculation. There is an excellent agreement.
> >
> > Now, I am trying to do the direct linear stability for RBC. But, I find there is a problem with the base flow addition for the buoyant scalar. I have reported this issue on the forum. Could you kindly also check this issue.
> >
> > Again, thanks for your response.
> >
> > With regards
> > Abhishek
> >
> >
> >
> > On Mon, Feb 5, 2018 at 5:15 PM, David Moxey <D.Moxey@exeter.ac.uk> wrote:
> > Hi Abhishek,
> >
> > These define the various choice of basis functions; the first is the modified C^0 basis that's defined in Karniadakis & Sherwin. The other two are Lagrange basis functions: the first is a choice with the number of quadrature points as one higher than the number of points; the other is where they are equal (i.e. the collocated basis with diagonal mass matrix).
> >
> > I believe all of those basis functions should work fine for 2D elements. For 3D, Lagrange only presently works for hex elements, whereas the C^0 has full support for hex/tet/prism/pyramid.
> >
> > Hope that helps,
> >
> > Dave
> >
> > > On 1 Feb 2018, at 17:42, Abhishek Kumar <abhishek.kir@gmail.com> wrote:
> > >
> > > Dear friends,
> > >
> > > I am new to NEKTAR++.
> > >
> > > Can someone tell me the difference between MODIFIED, GLL_LAGRANGE, GLL_LAGRANGE_SEM expansions type?
> > >
> > >
> > > With regards
> > > Abhishek Kumar
> > >
> > > ---------------------------------------------------------------------------------------
> > > Abhishek Kumar
> > > Post Doctoral Researcher
> > > Applied Mathematics Research Centre
> > > Coventry University, Coventry CV15FB
> > > The United Kingdom
> > >
> > > Email # ac7600@coventry.ac.uk, abhishek.kir@gmail.com
> > > ---------------------------------------------------------------------------------------
> > > _______________________________________________
> > > Nektar-users mailing list
> > > Nektar-users@imperial.ac.uk
> > > https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
> >
> >
> >
> >
> > --
> > With regards
> > Abhishek Kumar
> >
> > ---------------------------------------------------------------------------------------
> > Abhishek Kumar
> > Post Doctoral Researcher
> > Applied Mathematics Research Centre
> > Coventry University, Coventry CV15FB
> > The United Kingdom
> >
> > Email # ac7600@coventry.ac.uk, abhishek.kir@gmail.com
> > ---------------------------------------------------------------------------------------
> > _______________________________________________
> > Nektar-users mailing list
> > Nektar-users@imperial.ac.uk
> > https://mailman.ic.ac.uk/mailman/listinfo/nektar-users
>
>
>
>
> --
> With regards
> Abhishek Kumar
>
> ---------------------------------------------------------------------------------------
> Abhishek Kumar
> Post Doctoral Researcher
> Applied Mathematics Research Centre
> Coventry University, Coventry CV15FB
> The United Kingdom
>
> Email # ac7600@coventry.ac.uk, abhishek.kir@gmail.com
> ---------------------------------------------------------------------------------------

> <rbc_stability.xml>_______________________________________________

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