Curvature Effects using the Standard K Epsilon Model

syler3321 · October 19, 2010, 02:00

Hi,
I am simulating a flow over 2d hills. Curvature pretty much comes into the equation here. There will be an extra strain rate dv/dx. I am using the k epsilon model to run my simulation and playing with the curvature correction term does not exactly give accurate results. The maximum value allowed is 1.25. I am thinking about incorporating the richardson number into the k epsilon model. but since the richardson number is a function of dv/dx and du/dy, i would need to have a Cmu that is not invariant. I understand that CFX does not have the realizable k epsilon model in its list of models so this is a bugger. i have tried inputting a CCL function into Cmu but it returns an error message saying that i cannot input variables when defining Cmu. Any suggestions how i can tackle the effects of curvature?

Cheers
Ralph

ghorrocks · October 19, 2010, 17:51

The SST model has some curvature correction stuff available. Have you tried that?

syler3321 · October 19, 2010, 20:53

Hi Glenn,
i am trying to work with the k epsilon model only because it is pretty much the bread and butter of turbulence modelling. Also, my project is based on the k epsilon model. Is there a way I can edit the existing turbulence models in Ansys CFX. And by that i do not mean just changing the constants. i want to include the richardson number / curvature to the kinetic energy and dissipation equations. It would be awesome if i can just add on the terms to the preexisting models in CFX. Please advise.

Cheers
Ralph

October 19, 2010, 02:00	Curvature Effects using the Standard K Epsilon Model	#1
syler3321 Member ralph Join Date: Jun 2010 Location: Calgary Alberta Posts: 38 Rep Power: 15	Hi, I am simulating a flow over 2d hills. Curvature pretty much comes into the equation here. There will be an extra strain rate dv/dx. I am using the k epsilon model to run my simulation and playing with the curvature correction term does not exactly give accurate results. The maximum value allowed is 1.25. I am thinking about incorporating the richardson number into the k epsilon model. but since the richardson number is a function of dv/dx and du/dy, i would need to have a Cmu that is not invariant. I understand that CFX does not have the realizable k epsilon model in its list of models so this is a bugger. i have tried inputting a CCL function into Cmu but it returns an error message saying that i cannot input variables when defining Cmu. Any suggestions how i can tackle the effects of curvature? Cheers Ralph

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October 19, 2010, 17:51		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,701 Rep Power: 143	The SST model has some curvature correction stuff available. Have you tried that?

October 19, 2010, 20:53		#3
syler3321 Member ralph Join Date: Jun 2010 Location: Calgary Alberta Posts: 38 Rep Power: 15	Hi Glenn, i am trying to work with the k epsilon model only because it is pretty much the bread and butter of turbulence modelling. Also, my project is based on the k epsilon model. Is there a way I can edit the existing turbulence models in Ansys CFX. And by that i do not mean just changing the constants. i want to include the richardson number / curvature to the kinetic energy and dissipation equations. It would be awesome if i can just add on the terms to the preexisting models in CFX. Please advise. Cheers Ralph