Low Reynolds Airfoil Modeling In Fluent

morteza08 · October 23, 2011, 09:49

Hi. I am modeling anderson Spica airfoil in fluent.
the maximum velocity is 40m/s.
the Grid is CH
what is the best boundary condition for inlet outlet and upper and lower boundary.
which solver can predict the cl and cd more accurate.
what about under-relaxation factors? discretization methods and pressure velocity coupling?
I did not get good result by my own settings.
the residuals remain in high value. and cl and cd oscillate.

giuli@ · October 24, 2011, 06:03

I would put Pressure Far Field for all the boundaries.
kw-SST usually is the most accurate; but for airfoil you can use Spalart-Allmaras, is computationally cheaper than kw-SST and was developed especially for this application.
Under-relax factors: keep the default; if you have problem with convergence it can help if you lower them. But usually, if it does not converge, there must be a problem either in the formulation of the problem (BC) or in the mesh, or in the geometry..

Hope this help

cheers

morteza08 · October 31, 2011, 12:46

Thank you so much dear Guili

aerospaceman · November 23, 2011, 04:40

You have to watch out for transition, as none of the RANS models accurately captures it. Therefore your Cd maybe higher than results obtained in the literature. XFOIL should also help.

October 23, 2011, 09:49	Low Reynolds Airfoil Modeling In Fluent	#1
morteza08 Senior Member Morteza Join Date: May 2010 Location: Iran,Islamic Republic of Posts: 161 Rep Power: 15	Hi. I am modeling anderson Spica airfoil in fluent. the maximum velocity is 40m/s. the Grid is CH what is the best boundary condition for inlet outlet and upper and lower boundary. which solver can predict the cl and cd more accurate. what about under-relaxation factors? discretization methods and pressure velocity coupling? I did not get good result by my own settings. the residuals remain in high value. and cl and cd oscillate.

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October 24, 2011, 06:03		#2
giuli@ New Member FlowLy Join Date: Aug 2010 Location: Germany Posts: 18 Rep Power: 15	I would put Pressure Far Field for all the boundaries. kw-SST usually is the most accurate; but for airfoil you can use Spalart-Allmaras, is computationally cheaper than kw-SST and was developed especially for this application. Under-relax factors: keep the default; if you have problem with convergence it can help if you lower them. But usually, if it does not converge, there must be a problem either in the formulation of the problem (BC) or in the mesh, or in the geometry.. Hope this help cheers

October 31, 2011, 12:46		#3
morteza08 Senior Member Morteza Join Date: May 2010 Location: Iran,Islamic Republic of Posts: 161 Rep Power: 15	Thank you so much dear Guili

November 23, 2011, 04:40		#4
aerospaceman Member Join Date: Nov 2009 Posts: 43 Rep Power: 16	You have to watch out for transition, as none of the RANS models accurately captures it. Therefore your Cd maybe higher than results obtained in the literature. XFOIL should also help.