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Detached-Eddy Simulation (DES) models in OpenFOAM

Posted October 23, 2016 at 10:03 by fumiya

Detached-Eddy Simulation (DES) is a hybrid Reynolds Averaged Navier-Stokes (RANS)/Large-Eddy Simulation (LES) model.
The DES model was first proposed in 1997 by Spalart et al. [1] based on the Spalart-Allmaras RANS model and
it is commonly referred to as DES97.

I've summarized DES models available in OpenFOAM in the following post:
http://caefn.com/openfoam_turbulence_model_hybrid/

[1] P. R. Spalart, W.-H. Jou, M. Strelets and S. R. Allmaras,...
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A generalized thermal/dynamic wall function: Part 3

Posted October 17, 2016 at 11:25 by sbaffini (NuTBox)
Updated December 21, 2016 at 10:06 by sbaffini

In this post i summarize the initial problem and the procedure to determine the wall function value (i.e., the solution) for given y^+,F_T^+,Pr and Pr_t.

We looked for a solution T^+\left(y^+,F_T^+,Pr,Pr_t\right) to the problem:

\frac{dT^+}{dy^+}=\frac{Pr\left(1+F_T^+y^+\right)}{\left[1+\left(\frac{Pr}{Pr_t}\right)\left(\frac{\mu_t}{\mu}\right)\right]}

with:

\frac{\mu_t}{\mu}=\frac{\left(ky^+\right)^3}{\left(ky^+\right)^2+\left(ka_0\right)^3-\left(ka_0\right)^2}...
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File Type: txt wallfn.txt (2.2 KB, 76 views)
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A generalized thermal/dynamic wall function: Part 2

Posted October 17, 2016 at 08:24 by sbaffini (NuTBox)
Updated December 21, 2016 at 10:07 by sbaffini

In the first part of this post we left with the problem of computing the following integral:

f^+\left(y^+,\frac{Pr}{Pr_t}\right)=\int_0^{y+}{\frac{1}{\left[1+\left(\frac{Pr}{Pr_t}\right)\left(\frac{\mu_t}{\mu}\right)\right]}dz^+}

with:

\frac{\mu_t}{\mu}\left(y^+,a,k\right)=\frac{\left(ky^+\right)^3}{\left(ky^+\right)^2+\left(ka\right)^3-\left(ka\right)^2}

I added all the explicit functional dependencies here because we know f^+\left(y^+,1\right)...
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A generalized thermal/dynamic wall function: Part 1

Posted October 14, 2016 at 12:27 by sbaffini (NuTBox)
Updated December 21, 2016 at 10:07 by sbaffini

In a previous post i wrote about an extension of the Reichardt law of the wall to pressure gradient effects. That was derived by assuming the Reichardt profile as a solution for the case without pressure gradient and using integration by parts. In particular, given the the Reichardt function (k is the Von Karman constant):

f^+\left(y^+\right) = \frac{1}{k}\log\left(1+ky^+\right) +A\left(1-e^{-\frac{y^+}{B}}-\frac{y^+}{B}e^{-\frac{y^+}{C}}\right)

with:
...
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pimpleFoam vs simpleFoam vs pisoFoam vs icoFoam?

Posted October 14, 2016 at 11:27 by kindle
Updated October 24, 2016 at 11:37 by kindle

Quite confusing sometime !

But, why is that a problem needs boundary condition for U and p and all the other possible variables?

pisoFoam has relaxation coef while icoFoam does not have this.
Quote:
UEqn.relax();

Quote:
Originally Posted by ata View Post
Hi
icoFoam is transient solver for incompressible, laminar flow of Newtonian fluids.

pimpleFoam is large time-step transient solver for incompressible, flow using the PIMPLE(merged PISO-SIMPLE) algorithm.
...
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