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August 21, 2009, 19:55 |
Convergence criteria (II)
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#1 |
New Member
Daniel LLanes
Join Date: Aug 2009
Posts: 11
Rep Power: 16 |
Hi everybody:
Shall i consider a fluctuation between two constant (approximately) values as a convergence (in the semi-value of the fluctuation between peak and valley) without assuming a great mistake? Thx in advance!! |
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August 22, 2009, 05:09 |
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#2 |
New Member
Giuki Cael
Join Date: May 2009
Location: Belgium/The Netherlands
Posts: 13
Rep Power: 16 |
That depends on the convergence history and the amplitude of the convergence I would say. It depends which residual you are considering, maybe you could check the contours and see if somewhere an irregularity occurs, trying to adapt the mesh at those spots and see whether you still have fluctuations. Also you might check the skewness of your mesh...
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August 22, 2009, 06:27 |
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#3 |
New Member
Daniel LLanes
Join Date: Aug 2009
Posts: 11
Rep Power: 16 |
It´s fluctuating around its third-fourth significative number, whose order is 10x^-3. Enough for my Cl, Cd and Cm (i think...)
Ty m8!! |
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August 22, 2009, 06:32 |
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#4 |
New Member
Giuki Cael
Join Date: May 2009
Location: Belgium/The Netherlands
Posts: 13
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Is it the residual which is fluctuating or your Cl, Cd you are monitoring?
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August 22, 2009, 19:40 |
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#5 |
New Member
Daniel LLanes
Join Date: Aug 2009
Posts: 11
Rep Power: 16 |
Here is an example of the residuals. Almost constant, as you can see... Fluctuation of Cd, Cl and Cm is what expected (anything but weird ), peak-valley-peak-valley-peak-valley and so on...
Thank you m8!! |
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August 22, 2009, 21:41 |
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#6 |
Member
Join Date: Apr 2009
Posts: 78
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In my experience residuals on the order of 1e-5 are small enough to consider it converged. I would consider the case converged in your case, assuming the amplitude of the oscillations aren't too large.
That said, I've seen residuals less than 1e-5 for Cl for a circulation-control airfoil and yet the magnitude of oscillations for Cl were on the order of 1 (for an airfoil with an expected Cl of around 6.) In that case, the problem turned out to be three-fold: highly skewed cells in areas of high gradients, too large of cells in these areas, and large area changes. Have you tried grid adaption based on gradients? Another thing to check would be the under-relaxation factors and courant number. Try increasing all of those to see if it either causes divergence or convergence. |
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August 23, 2009, 06:13 |
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#7 |
New Member
Daniel LLanes
Join Date: Aug 2009
Posts: 11
Rep Power: 16 |
Ty m8s, this has been (is being) useful for me
Cheers!! |
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August 23, 2009, 20:28 |
Vibrational Analysis
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#8 |
New Member
Sri
Join Date: Aug 2009
Posts: 1
Rep Power: 0 |
Hello Everyone
Could any one please help me with vibrational Analysis. I am carrying Vibrational Analysis on a Fuel Rail, if i want to add mass of the fuel during Modal analysis, how can i do ?? Please help me out. Last edited by csri07; August 23, 2009 at 20:59. |
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