Literature on Calculating the resolved and unresolved TKE

Falu · March 14, 2021, 04:42

Hey Guys,

I found in this forum a link to the Ansys CFX Support Forum, in which a definition for the resolved and unresolved Turbulent Kinetic Energy is found:

https://forum.ansys.com/discussion/2...kinetic-energy

Im interested in this calculation, but i cant find any literature to support this definition of the TKE. Does someone know a good source?

ghorrocks · March 15, 2021, 03:21

The reference I use for most turbulence calculations is "Turbulence Modelling for CFD" by Wilcox.

Falu · March 16, 2021, 04:57

I have taken a look, but there i only find the resolved TKE formulation, like i most of the time do when im searching for this topic. LES ist listed in this book under "New Horizons", I think its to old to have information of the energy of the unresolved part? Do you know another literature regarding this topic?

ghorrocks · March 16, 2021, 06:07

If you don't like my reference then you can find your own. Doing a literature study is an important skill for a researcher, so it is time to get some practise.

Falu · March 17, 2021, 06:34

I really dont have anything against your literature, in fact im referencing myself often this literature. I just think it doenst provide any answer to the above mentioned question, or am getting something wrong here? This might be the case!

Im really having trouble to understand the formulation in the forum post. I think its just a modification of the eddy viscosity in the smagorinsky model: v_t=(C_s*(dxdydz)^(1/3))^2*|bar(S)|. But I really dont find any literature, giving a context between |bar(S)| and (1/3)*ShearStrainRate ?

Opaque · March 17, 2021, 07:33

Would you mind sharing how you would compute the turbulent kinetic energy for the Smagorinsky LES model regardless of CFD software being used?

Falu · March 19, 2021, 15:59

I found two sources which helped me to figure it out.

In "Nonequilibrium energy spectrum in the subgrid-scale one-equation model in large-eddy simulation" by Horiuti and "Sub-grid Scale Modeling in Large Eddy Simulation with Variable Eddy-Viscosity Coefficient" are in my opionen two very good derivations. But I still dont get the 1/0.3 pre-factor in the equation from the official ansys forum

March 14, 2021, 04:42	Literature on Calculating the resolved and unresolved TKE	#1
Falu New Member Fab Join Date: Nov 2020 Posts: 25 Rep Power: 5	Hey Guys, I found in this forum a link to the Ansys CFX Support Forum, in which a definition for the resolved and unresolved Turbulent Kinetic Energy is found: https://forum.ansys.com/discussion/2...kinetic-energy Im interested in this calculation, but i cant find any literature to support this definition of the TKE. Does someone know a good source?

March 15, 2021, 03:21		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	The reference I use for most turbulence calculations is "Turbulence Modelling for CFD" by Wilcox. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

March 16, 2021, 06:07		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	If you don't like my reference then you can find your own. Doing a literature study is an important skill for a researcher, so it is time to get some practise. Opaque and aero_head like this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

March 17, 2021, 07:33		#6
Opaque Senior Member Join Date: Jun 2009 Posts: 1,804 Rep Power: 32	Would you mind sharing how you would compute the turbulent kinetic energy for the Smagorinsky LES model regardless of CFD software being used? aero_head likes this. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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March 16, 2021, 04:57		#3
Falu New Member Fab Join Date: Nov 2020 Posts: 25 Rep Power: 5	I have taken a look, but there i only find the resolved TKE formulation, like i most of the time do when im searching for this topic. LES ist listed in this book under "New Horizons", I think its to old to have information of the energy of the unresolved part? Do you know another literature regarding this topic?

March 17, 2021, 06:34		#5
Falu New Member Fab Join Date: Nov 2020 Posts: 25 Rep Power: 5	I really dont have anything against your literature, in fact im referencing myself often this literature. I just think it doenst provide any answer to the above mentioned question, or am getting something wrong here? This might be the case! Im really having trouble to understand the formulation in the forum post. I think its just a modification of the eddy viscosity in the smagorinsky model: v_t=(C_s(dxdydz)^(1/3))^2\|bar(S)\|. But I really dont find any literature, giving a context between \|bar(S)\| and (1/3)*ShearStrainRate ?

March 19, 2021, 15:59		#7
Falu New Member Fab Join Date: Nov 2020 Posts: 25 Rep Power: 5	I found two sources which helped me to figure it out. In "Nonequilibrium energy spectrum in the subgrid-scale one-equation model in large-eddy simulation" by Horiuti and "Sub-grid Scale Modeling in Large Eddy Simulation with Variable Eddy-Viscosity Coefficient" are in my opionen two very good derivations. But I still dont get the 1/0.3 pre-factor in the equation from the official ansys forum