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Hi Markus, hi Espressis,
I'm not aware of of the OIF tutorial, but you can not expect the
results to be equivalent. Simple reason: With the rhomboid you
define the velocity everywhere on the inlet. Across the channel
cross section, the velocity is constant. In the Poisseuille case,
the flux is not constant but parabolic. If you had a long channel,
far away from the inlet BC, you would obtain Poisseuille-type
behaviour, but towards the in- and outlet the flow field gets
closer and closer to the applied BC. You can known the maximum
velocity far away from the center by assuming an unknown pressure
gradient in the center and setting the total flux through the
center identical to the flux over the boundary. This equation you
can solve for v_max.
Attached, you'll find the flow field obtained by your simulation.
It clearly becomes more Poisseuille-ish at the center.
Cheers
Stefan
On 03/07/2014 01:48 PM, Wink, Markus wrote:
Dear
Espresso-community,
I
have got a question concerning the fluid flow between two
plates (again). On the one hand, I have simulated it
introducing a force density of 64000N/m^3. This should (in
my system) result in a maximum velocity of 0.02m/s. This is
what I get. Now I have tried setting up a rhomboid with a
certain velocity so that the momentum is transferred to the
fluid and the flow profile is achieved (the OIF-tutorial
says, that way, the simulation should be faster).
Surprisingly, this results in a max. velocity of the flow
profile of 0.026 m/s, even though the velocity of the
rhomboid is set to 0.02 m/s. Does anyone has a clue where
this discrepancy comes from?
Attached
you will find the simulation scripts and the relaxed
velocity profiles.
Greetings
Markus
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wink.pdf