Courant number in steady, coupled solver

sunilpatil · April 3, 2016, 23:06

Hello everyone,
I am running a steady case with coupled solver. For low values of courant number solution converges is it my final solution should be independent of courant number or can I accept low courant number converged results without further increasing the courant number.

LuckyTran · April 6, 2016, 09:09

The Courant number is like an under-relaxation factor. If you increase it you can amplify numerical oscillations that cause your solution to diverge, increasing urf's also does the same.

The low Courant number solution should be okay as long as you didn't put a ridiculously small number for the Courant number. I think the default is now 50 (it used to be 200 in some versions). It's hard to tell if your solution is converged or not with small urf's and Courant numbers. Sometimes people put 1e-6 for their urf's and think they have a converged solution...

April 3, 2016, 23:06	Courant number in steady, coupled solver	#1
sunilpatil Senior Member sunil Join Date: Jul 2012 Location: Bangalore Posts: 179 Rep Power: 13	Hello everyone, I am running a steady case with coupled solver. For low values of courant number solution converges is it my final solution should be independent of courant number or can I accept low courant number converged results without further increasing the courant number. __________________ Regards, Sunil

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April 6, 2016, 09:09		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,668 Rep Power: 65	The Courant number is like an under-relaxation factor. If you increase it you can amplify numerical oscillations that cause your solution to diverge, increasing urf's also does the same. The low Courant number solution should be okay as long as you didn't put a ridiculously small number for the Courant number. I think the default is now 50 (it used to be 200 in some versions). It's hard to tell if your solution is converged or not with small urf's and Courant numbers. Sometimes people put 1e-6 for their urf's and think they have a converged solution...