Add a lag correction equation

Saeef · May 16, 2019, 11:49

It has been resolved

ghorrocks · May 16, 2019, 19:23

If you included some details of what you are modelling and how you modelled it we might be able to help you.

Saeef · May 16, 2019, 22:32

Quote:

Originally Posted by ghorrocks

If you included some details of what you are modelling and how you modelled it we might be able to help you.

It's a correlation for non equilibrium turbulent flows proposed by Olsen(2001).

Olsen, M., & Coakley, T. (2001). The lag model, a turbulence model for non equilibrium flows. In 15th AIAA Computational Fluid Dynamics Conference (p. 2564).

Gert-Jan · May 17, 2019, 05:17

Don't know anything about your model, application or whatsoever. So, it is difficult to help, as Glenn already mentioned.
However in your KVN equation, you are dividing by a variable which can become zero. This is a source of troubles. Therefore, please make sure that this cannot occur by using min, max, abs or other numerical operators.

Opaque · May 22, 2019, 11:58

A bit more information on your model will help you obtaining suggestions.

So far, you have shown the equation you intend to solve and that you have not been able to converge the solution; however, no details on how you set it up in ANSYS CFX.

Saeef · May 23, 2019, 03:47

Quote:

Originally Posted by Opaque

A bit more information on your model will help you obtaining suggestions.

So far, you have shown the equation you intend to solve and that you have not been able to converge the solution; however, no details on how you set it up in ANSYS CFX.

There's no difference with normal simulations, only a lag of eddy viscosity needs adding. The lag equation was added by the CFX additional variable method, which was illustrated in the PDF file.

May 16, 2019, 11:49	Add a lag correction equation	#1
Saeef New Member Zhiyuan Liu Join Date: Oct 2018 Location: China Posts: 26 Rep Power: 8	It has been resolved Last edited by Saeef; June 5, 2019 at 09:20. Reason: It has been resolved

May 16, 2019, 19:23		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,871 Rep Power: 144	If you included some details of what you are modelling and how you modelled it we might be able to help you. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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May 17, 2019, 05:17		#4
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,928 Rep Power: 28	Don't know anything about your model, application or whatsoever. So, it is difficult to help, as Glenn already mentioned. However in your KVN equation, you are dividing by a variable which can become zero. This is a source of troubles. Therefore, please make sure that this cannot occur by using min, max, abs or other numerical operators.

May 22, 2019, 11:58		#5
Opaque Senior Member Join Date: Jun 2009 Posts: 1,880 Rep Power: 33	A bit more information on your model will help you obtaining suggestions. So far, you have shown the equation you intend to solve and that you have not been able to converge the solution; however, no details on how you set it up in ANSYS CFX.