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May 1, 2016, 02:18 |
Lift Vs Drag?
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#1 |
New Member
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Hello everyone,
In ANSYS FLUENT: for flow over a object, Could anyone tell me why the coefficient of drag reaches a constant value whereas the Coefficient of lift oscillates over time? Thanks in advance for the reply. Last edited by Vamsi; May 1, 2016 at 14:03. |
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May 2, 2016, 04:28 |
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#2 |
Senior Member
david
Join Date: Oct 2012
Posts: 142
Rep Power: 13 |
it simply means your solution is not converged. This is of course if you are running a steady state case.
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May 2, 2016, 05:39 |
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#3 |
New Member
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May 3, 2016, 03:38 |
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#4 |
Senior Member
Hamid Zoka
Join Date: Nov 2009
Posts: 288
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Hi
If there is no separation around your object constant drag coefficient can be related to viscousity which acts as a damper and can suppress the falucctuations. While the lift comes from pressure distributions on the surfaces of the object and can be subject to change when you run a time dependet simulation. Wakes and other time dependent flow structures can simply affect pressure distributions as time passes. Regards |
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May 3, 2016, 22:12 |
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#5 | |
New Member
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Quote:
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May 4, 2016, 11:55 |
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#6 |
New Member
Join Date: Dec 2014
Posts: 3
Rep Power: 11 |
If you are doing a transient analysis with turbulence options checked, there is no reason to expect a constant C_l value. At each instant in time the separated flow leaves a chaotic turbulent wake (no matter how small).
I think in an unsteady situation like this, a steady C_l / C_d value doesn't mean much. |
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May 4, 2016, 11:57 |
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#7 |
Senior Member
Join Date: Dec 2011
Location: Madrid, Spain
Posts: 134
Rep Power: 15 |
Hello,
I am no expert in the subject but it could be that your simulation is capturing the right behaviour. You might want to check the Strouhal number of the vortex shedding from your simulations against experimental and numerical data from the literature. There are plenty of papers on the matter, just google "flow past a square cylinder". Cheers, Michujo. |
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May 8, 2016, 16:00 |
drag coef
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#8 |
New Member
lazzouni rima
Join Date: Apr 2016
Posts: 3
Rep Power: 10 |
how to have the drag coef in fluent thanks
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