[FLASH-USERS] Flow Reversal for Windtunnel with Gravity

[dongwook at flash.uchicago.edu]

Hi Nitesh,

I am not sure if anyone has replied to your email, but if not, I am sorry
that your email has not been anwered yet.

Just few questions to understand your issue:

(1) To what direction do you apply your constant gravity? Is this to the
negetive x-direction, and as a result, do you see flow reversal at the
xl-boundary?

The Windtunnel uses inflow boundary condition at the xl-boundary, and this
should not allow any matter to leave across the boundary. But if your
gravity is applied to the negative x-direction, it may as well be the case
that flow reversal would happen (depending on how strong your gravity is
relative to the inflow velocity), but the inflow boundary condition at the
xl-boundary doesn't seem to be a sensible thing to have.

(2) In case that your gravity is NOT to the negative x-direction but still
experiencing the flow reversal, it could be useful for you to understand
your problem by trying several things:

  (i) change gravity directions and identify which one has the flow reversal,
  (ii) change the magnetitude of gravity and identify the problems as a
function of its magnitude,
  (iii) use an alternative solver, for example, if you use the split PPM
then use the unsplit hydro solver, or vice versa.

(3) By the way, what FLASH do you use? Do you use the most recent release?

Hope this helps.

Best,
Dongwook
=========================================
Dongwook Lee, Ph.D., Research Scientist
The Flash Center for Computational Science
The University of Chicago
5747 S. Ellis Ave., Room 319
Chicago, IL 60637
(773) 834-6830

> Hello All,
> I intend to perform a Multi-species laminar buoyant Jet simulation.
> I began with the turning on Gravity in the Supplied Windtunnel test
> problem.
> The Windtunnel test problem when ran with constant Gravity results into
> complete flow reversal (towards xl-boundary). Even when the xl-boundary
> is made outflow flow reversal is observed.
> Is this a known issue? Could some one suggest how to overcome this?
> Thanks,
> Nitesh
>