Reynolds stress calculation in Starccmplus

jahed1775 · July 8, 2012, 15:28

Hey guys, can anyone help how to get reynolds shear stress in starccmplus from k-epsilon or v2f model. Will really appreciate.

Jahed

flotus1 · July 8, 2012, 17:02

The components of the Reynolds stress tensor are not available with a k-epsilon model.
The turbulent kinetic energy k only represents the values on the diagonal of the reynolds stress tensor -> k=1/2*(uu+vv+ww)

The individual components are only accessible with a Reynolds-stress turbulence model, a LES or a DNS.

Far · July 9, 2012, 04:57

Can we find them through velocity gradients and eddy viscosity?

flotus1 · July 9, 2012, 07:48

Unfortunately, we can't.
That is one of the disadvantages of two-equation turbulence models.
We only have two equations for turbulence quantities. The Reynolds stress tensor contains 6 independent variables.

Unless we use a turbulence model with 6 additional equations (like a reynolds stress model) or we obtain the reynolds stresses explicitly wit a LES or DNS, we don't have enough information about the flow to give an estimate for the individual components of the Reynolds stresses.

July 8, 2012, 15:28	Reynolds stress calculation in Starccmplus	#1
jahed1775 New Member Jahed Join Date: Jul 2012 Posts: 3 Rep Power: 13	Hey guys, can anyone help how to get reynolds shear stress in starccmplus from k-epsilon or v2f model. Will really appreciate. Jahed

July 8, 2012, 17:02		#2
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,399 Rep Power: 46	The components of the Reynolds stress tensor are not available with a k-epsilon model. The turbulent kinetic energy k only represents the values on the diagonal of the reynolds stress tensor -> k=1/2*(uu+vv+ww) The individual components are only accessible with a Reynolds-stress turbulence model, a LES or a DNS. jzc likes this.

July 9, 2012, 07:48		#4
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,399 Rep Power: 46	Unfortunately, we can't. That is one of the disadvantages of two-equation turbulence models. We only have two equations for turbulence quantities. The Reynolds stress tensor contains 6 independent variables. Unless we use a turbulence model with 6 additional equations (like a reynolds stress model) or we obtain the reynolds stresses explicitly wit a LES or DNS, we don't have enough information about the flow to give an estimate for the individual components of the Reynolds stresses. jzc likes this.

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July 9, 2012, 04:57		#3
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	Can we find them through velocity gradients and eddy viscosity?