[Nek5000-users] Fwd: Variable density flows

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

I remember looking at variable density flow equations long time ago in the context of R. T. instability
and what I recall is that the governing equations are pretty much the same as the low Mach ones w/o source terms
see for example ( The mixing transition in Rayleigh–Taylor instability Journal of Fluid Mechanics / Volume 511 / July 2004,	 pp 333-362)
you will need to have two passive scalars in addition to the mass and momentum equations.

Ammar



On Oct 11, 2013, at 11:54 AM, nek5000-users at lists.mcs.anl.gov wrote:

> Hi Paul
> 
> For variable density case do I need to use the low mach number version or some other way ?
> 
> Thanks
> praveen
> 
> 
> On Fri, Oct 11, 2013 at 8:24 PM, <nek5000-users at lists.mcs.anl.gov> wrote:
> 
> In principle, this should work with the Pn-Pn-2 STRESS formulation, but
> I don't think it has been thoroughly tested.
> 
> Regarding large viscosity variations, work needs to be done on the
> preconditioners for the viscous terms.   This hasn't been a traditional
> focus for Nek5000, which has been aimed at high Reynolds number flows
> where the viscous solves are essentially trivial (compared to the
> pressure, say).
> 
> Certainly, there are things that could be done to be effective in
> this space.  I would start by running some test problems with the
> STRESS formulation to see if you get the accuracy you're after.  If
> so, then we can look into performance enhancement via better preconditioning
> strategies for the case at hand.
> 
> HTH,
> 
> Paul
> 
> ----- Original Message -----
> From: nek5000-users at lists.mcs.anl.gov
> To: "nek5000" <nek5000-users at lists.mcs.anl.gov>
> Sent: Friday, October 11, 2013 9:16:24 AM
> Subject: [Nek5000-users] Fwd: Variable density flows
> 
> 
> 
> Hello
> 
> 
> 
> 
> 
> Can we solve variable density incompressible flows with nek5000 ? For e.g. see the model given by eq. 2.1 here
> 
> 
> http://www.math.tamu.edu/~guermond/PUBLICATIONS/guermond_quartapelle_JCP_2000.pdf
> 
> 
> 
> Also, can nek handle variable viscosity with large variations ?
> 
> 
> Thanks
> praveen
> 
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