[Nek5000-users] Corner elements giving large values

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

Hi Swarandeep,

How large is your Rayleigh number and what is your resolution?
What are your thermal bcs?  What are your ICs?

There should be no particular issue with your configuration - but you do need to
control spatial and temporal resolution.


For RB, you often have to start at low Ra and/or small dt because the nonlinear
response can often drive the velocities to be quite high very rapidly before the
CFL constraint kicks in.   RB flows are one of the rare instances where I use
variable time step size (param 12 > 0), but even then you have to keep the target
CFL quite small until the flow is established.

hth,

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: Thursday, June 01, 2017 7:27 AM
To: nek5000-users at lists.mcs.anl.gov
Subject: [Nek5000-users] Corner elements giving large values

Dear Nek forum,

      I am simulating Rayleigh Benard flow in a 3D finite cylindrical annulus.
      I am getting spurious large values of velocity at the corner regions
      of the annulus i.e. the edges where the inner cylinder joins the
top and bottom
      planes. The boundary condition is no-slip and no penetration for velocity
      at these edges. Can someone point out a plausible reason.

Thank you
Swarandeep
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