Implementing a new turbulent diffusion coefficient

MR7 · August 1, 2020, 15:58

Dear Foamers,

The buoyantBousinessqPimpleFoam solver uses the following equation for turbulent diffusion coefficient based on Standard Gradient Diffusion Hypothesis (SGDH):

$alpha_t = \nu_t / Pr_t$

I'm going to modify this equation based on Generalized Gradient Diffusion Hypothesis (GGDH) as follows:

$alpha_t =-\frac{3}{2}\frac{C_\mu}{Pr_t}\overline{u'u'}$

The problem is that I don't know how i can access to $\overline{u'u'}$ . I tried

Code:

turbulence->R()

but it didn't work. It would be appreciated if someone help me to solve this problem.

mAlletto · August 3, 2020, 15:40

If you want the first component of the symmetric tensor R you can try

Code:

turbulence->R().xx()

August 1, 2020, 15:58	Implementing a new turbulent diffusion coefficient	#1
MR7 New Member Mohammadmehdi Join Date: Feb 2019 Posts: 4 Rep Power: 7	Dear Foamers, The buoyantBousinessqPimpleFoam solver uses the following equation for turbulent diffusion coefficient based on Standard Gradient Diffusion Hypothesis (SGDH): $alpha_t = \nu_t / Pr_t$ I'm going to modify this equation based on Generalized Gradient Diffusion Hypothesis (GGDH) as follows: $alpha_t =-\frac{3}{2}\frac{C_\mu}{Pr_t}\overline{u'u'}$ The problem is that I don't know how i can access to $\overline{u'u'}$ . I tried Code: turbulence->R() but it didn't work. It would be appreciated if someone help me to solve this problem.

August 3, 2020, 15:40		#2
mAlletto Senior Member Michael Alletto Join Date: Jun 2018 Location: Bremen Posts: 615 Rep Power: 15	If you want the first component of the symmetric tensor R you can try Code: turbulence->R().xx()

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