Make modifications on the Lagrangian stochasticDispersionRAS model

marialhm · August 10, 2018, 06:40

Dear all,

I'm using the Lagrangian stochasticDispersionRAS model to simulate the dispersion of particles suspended in turbulence. But the stochasticDispersionRAS model in OpenFOAM just describes homogeneous flows. In inhomogeneous flows, it needs to add a drift correction. The total equation describing the stochastic dispersion model is shown in the figure in the attachment.

But now I have problems with programming because, in the Lagrangian codes, all the parameters we got are scalars or vectors, but the last term in the equation needs velocity of volVectorField. I don't know how to solve this now.

Anyone has the idea of the programming?

Thanks in advance.

Maria

marialhm · August 10, 2018, 06:42

The equation is in the attachment, sorry for forgetting it.

Scram_1 · February 15, 2020, 20:26

Hi marialhm!
I believe you are trying to incorporate the Langevin equations in your turbulent dispersion model.
Did you succeed in getting it to work with OpenFOAM? If yes, then can you share how you went about coding the drift correction term?

Thanks
Scram_1

zhangyan · February 16, 2020, 10:54

I found a reference,
On this webpage:
http://www.tfd.chalmers.se/~hani/kurser/OS_CFD/
search:
Modification of Stochastic Model in Lagrangian Tracking Method

Scram_1 · February 16, 2020, 11:02

Thanks for your reply zhangyan!
I have seen that reference before. But I believe that is just a modification of the current isotropic dispersion model in OF to account for anisotropy. That does not solve for the Langevin equations.

joshwilliams · November 23, 2022, 09:36

My GitHub repository has implemented the Langevin equation in OpenFOAM for LES. We have given a test case of decaying homogeneous isotropic turbulence. It would be simple to adapt it for RAS turbulence if necessary.

Importantly, the closures we use in this repository for drift and diffusion are inferred from machine learning models. But, it is also simple to adapt for theoretical closures for drift and diffusion (e.g. Pope's simplified Langevin model)

August 10, 2018, 06:40	Make modifications on the Lagrangian stochasticDispersionRAS model	#1
marialhm Member Maria Join Date: Jul 2013 Posts: 84 Rep Power: 12	Dear all, I'm using the Lagrangian stochasticDispersionRAS model to simulate the dispersion of particles suspended in turbulence. But the stochasticDispersionRAS model in OpenFOAM just describes homogeneous flows. In inhomogeneous flows, it needs to add a drift correction. The total equation describing the stochastic dispersion model is shown in the figure in the attachment. But now I have problems with programming because, in the Lagrangian codes, all the parameters we got are scalars or vectors, but the last term in the equation needs velocity of volVectorField. I don't know how to solve this now. Anyone has the idea of the programming? Thanks in advance. Maria

February 16, 2020, 10:54		#4
zhangyan Senior Member Yan Zhang Join Date: May 2014 Posts: 120 Rep Power: 11	I found a reference, On this webpage: http://www.tfd.chalmers.se/~hani/kurser/OS_CFD/ search: Modification of Stochastic Model in Lagrangian Tracking Method __________________ https://openfoam.top

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February 15, 2020, 20:26		#3
Scram_1 Member Join Date: Oct 2015 Posts: 63 Rep Power: 10	Hi marialhm! I believe you are trying to incorporate the Langevin equations in your turbulent dispersion model. Did you succeed in getting it to work with OpenFOAM? If yes, then can you share how you went about coding the drift correction term? Thanks Scram_1

February 16, 2020, 11:02		#5
Scram_1 Member Join Date: Oct 2015 Posts: 63 Rep Power: 10	Thanks for your reply zhangyan! I have seen that reference before. But I believe that is just a modification of the current isotropic dispersion model in OF to account for anisotropy. That does not solve for the Langevin equations.

November 23, 2022, 09:36		#6
joshwilliams Senior Member Josh Williams Join Date: Feb 2021 Location: Scotland Posts: 112 Rep Power: 5	My GitHub repository has implemented the Langevin equation in OpenFOAM for LES. We have given a test case of decaying homogeneous isotropic turbulence. It would be simple to adapt it for RAS turbulence if necessary. Importantly, the closures we use in this repository for drift and diffusion are inferred from machine learning models. But, it is also simple to adapt for theoretical closures for drift and diffusion (e.g. Pope's simplified Langevin model)