Reliability of 3d urans

anandsudhi · December 7, 2015, 05:22

Hi

How reliable is the accuracy of 3D URANS. Is it always better to go for LES or DES in 3D cases or is 3D URANS sufficient for calculation of mean quantities like Drag values.

robo · December 7, 2015, 08:38

What is the source of the unsteadiness, and what size are your time steps with respect to the larger turbulent fluctuations? URANS is not well formulated as you refine your timestep, and it's accuracy will strongly depend on the character of the unsteadiness you're trying to capture. Note that it also has all the short comings of regular steady-state RANS as well; so if your flow contains strong anisotropy then it would also not be that accurate for example...

December 7, 2015, 05:22	Reliability of 3d urans	#1
anandsudhi New Member anand sudhi Join Date: Sep 2015 Posts: 16 Rep Power: 10	Hi How reliable is the accuracy of 3D URANS. Is it always better to go for LES or DES in 3D cases or is 3D URANS sufficient for calculation of mean quantities like Drag values.

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December 7, 2015, 08:38		#2
robo Member robo Join Date: May 2013 Posts: 47 Rep Power: 12	What is the source of the unsteadiness, and what size are your time steps with respect to the larger turbulent fluctuations? URANS is not well formulated as you refine your timestep, and it's accuracy will strongly depend on the character of the unsteadiness you're trying to capture. Note that it also has all the short comings of regular steady-state RANS as well; so if your flow contains strong anisotropy then it would also not be that accurate for example...