[Nek5000-users] Infinite Prandtlnumber with Nek5000

[nek5000-users at lists.mcs.anl.gov]

Hi Jan,

I just saw this and the follow-on posts.  (Apologies - have been on the road for
several weeks.)

I've not tried this, but it appears to me that you simply will set IFNAV = F in the .rea 
file and can set param(1) [ rho ] to be a very small number.  Param(2) is the dynamic
viscosity, so you can set that independently of param(1).   This will have the affect
of forcing the velocity to relax very quickly (its inertia is negligible compared to the
other terms in the momentum equation).  So, you could conceivably set param(1)
to be 1.e-30, say.

Note that, on the same line where IFNAV is set, you would set IFADV to be "T" for
the second field.  It should look something like:

F T F F F F F F F F F IFNAV & IFADVC (convection in P.S. fields)

Also, you might find it of value in this scenario to try the Pn-Pn-2 formulation with
plan1 ...  In this case, you would indeed want to edit the source --- specifically:

change the call to plan3() to call plan1()  in drive2.f ...    As I say, I've not experimented
with this flow regime so am only making suggestions to try, rather than firm
recommendations based on experience.

Paul

________________________________________
From: nek5000-users-bounces at lists.mcs.anl.gov [nek5000-users-bounces at lists.mcs.anl.gov] on behalf of nek5000-users at lists.mcs.anl.gov [nek5000-users at lists.mcs.anl.gov]
Sent: Wednesday, August 05, 2015 5:15 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] Infinite Prandtlnumber with Nek5000

Hi all,
I was wondering if it is possible to use Nek5000 for simulations in the
infinite Prandtlnumber regime (e.g. planetary mantles). This would
require to solve the NS Stokes equation without the time derivative and
advection term and the heat equation for T:

1) Solve visc * laplace u - grad p + buoyancy = 0 and div u = 0, where
bouyancy depends on a given T field and a Rayleigh number
2) Update T by solving dT/dt + u grad T = diff * laplace T (+ other sources)
3) go back to 1 with the new T field, repeat

More realistic models would then use a varying viscosity.
I looked at the steady state example (kov_st_state), but this is missing
the time depencence via the Temperature. Any hints on the possibility
would be much appreciated.

Thanks,
Jan

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