Which flow solver is solved in turbulence flows in starccm+ ?

kailashpp1990 · March 27, 2017, 05:27

I have some basic doubts regarding the solver in starccm+. I am using segregated flow solver with Realizable k_epsilon_turbulence (RANS is activated by default). Which governing equations are solved here ? Continuity equation and momentum balance according to segregated flow or RANS ?

me3840 · March 27, 2017, 09:33

I'm not sure I understand your question. I don't think the 'segregated flow' equations exist?

You are using a RANS turbulence model, so yes, you are solving the RANS equations. The segregated solver is just the algorithm used to solve those equations.

LuckyTran · April 1, 2017, 22:26

Yeah you're using two questions with the appearance of one. Flow solvers are solvers, they do the solving, they don't get solved.

The flow solver is a solver that solves equations.

RANS + turbulence models are equations that need to be solved.

juliom · April 2, 2017, 07:24

Deal Colleagues;
RANS equations are the same Navier stokes equations (mass, momentum and energy) but averaged. It means that you always solve the same equations, either you averaged them or you filter them. In DNS you do not do none f the previous.
The turbulence model is the model you used to MODEL or represent the turbulence stresses.
In principle you can avoid using the turbulence models (K-E, K-W etc) if you have information about the Reynolds stress tensor, which is not usually the case, therefore you need the turbulence model.

March 27, 2017, 05:27	Which flow solver is solved in turbulence flows in starccm+ ?	#1
kailashpp1990 New Member Kailash Join Date: Sep 2015 Posts: 8 Rep Power: 10	I have some basic doubts regarding the solver in starccm+. I am using segregated flow solver with Realizable k_epsilon_turbulence (RANS is activated by default). Which governing equations are solved here ? Continuity equation and momentum balance according to segregated flow or RANS ?

March 27, 2017, 09:33		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 24	I'm not sure I understand your question. I don't think the 'segregated flow' equations exist? You are using a RANS turbulence model, so yes, you are solving the RANS equations. The segregated solver is just the algorithm used to solve those equations. lcarasik likes this.

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April 1, 2017, 22:26		#3
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 65	Yeah you're using two questions with the appearance of one. Flow solvers are solvers, they do the solving, they don't get solved. The flow solver is a solver that solves equations. RANS + turbulence models are equations that need to be solved.

April 2, 2017, 07:24		#4
juliom Senior Member Julio Mendez Join Date: Apr 2009 Location: Fairburn, GA. USA Posts: 290 Rep Power: 18	Deal Colleagues; RANS equations are the same Navier stokes equations (mass, momentum and energy) but averaged. It means that you always solve the same equations, either you averaged them or you filter them. In DNS you do not do none f the previous. The turbulence model is the model you used to MODEL or represent the turbulence stresses. In principle you can avoid using the turbulence models (K-E, K-W etc) if you have information about the Reynolds stress tensor, which is not usually the case, therefore you need the turbulence model.