CFD Online Discussion Forums - Choosing Exact boundary Conditions

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Choosing Exact boundary Conditions

Hi Foamers,

I am trying to reproduce a simple result by buoyantBoussinesqSimpleFoam solver (OpenFoam 3.1.1 version). I have already set the simulation but not sure whether the set up is 100% correct or not. The description of the problem is attached here. This is basically a laminar case. I took geometry according to this paper. I think the difficulty is in choosing boundary conditions. I have chosen my boundary conditions according to the attached problem is as follows,

Quote:

Velocity:
Hot wall – fixedValue, uniform (0 0 0)
Top and Bottom wall - fixedValue, uniform (0 0 0)
Open boundary – zeroGradient
Default faces-empty

Temperature:
Hot wall – fixedValue, uniform 333
Top and Bottom wall - zeroGradient
Open boundary – inletOutlet, Inletvalue - uniform 289, value- 289
Default faces-empty

P_rgh:
Hot wall – fixedFluxPressure, rho-rhok, uniform 0
Top and Bottom wall- fixedFluxPressure, rho-rhok, uniform 0
Open boundary – fixedValue, uniform 0
Default faces-empty

P:
Hot wall – Calculated (0)
Top and Bottom wall - Calculated (0)
Open boundary – Calculated (0)
Default faces-empty

I have got some result but it is not similar to that related problem.

Can anyone tell what is the mistake that I choose in my boundary conditions based on the OpenFOAM solvers?

Any suggestion please?

Hi!

Can you share the paper and/or your case?
Your BCs seems to be fine, but maybe they did some fancy stuff in the paper.

Your constants in the boussinesq approximation are correct?
Your mesh is good enough? (I think you made a pure hex mesh with blockMesh so i think it's okay)
The mesh resolution is fine enough at the wall?
Your g is correct?
You reached convergence?

Sorry for these basic questions but sometimes a typo ruins everything.

Quote:

Originally Posted by simrego (Post 718290)

Hi Simrego,

Sorry for my late reply as I was away from my desk for the weekend. However, Thank you for your valuable response. Here I attached my case file. Now I am trying by buoyantBoussinesqPimpleFoam that is quite similar to buoyantBoussinesqSimpleFoam. Because of the size, I could not attach the paper here. But I am giving you the Google drive link. Just copy and paste it.

Quote:

https://drive.google.com/file/d/1W7C...ew?usp=sharing

And let know please what is the mistake that I am doing each time. Thank you in advance. Looking for your response.

Hi Simrego,

Did you check that yet?

Boundary Conditions

Quote:

Originally Posted by Mondal131211 (Post 718551)

Can anyone correct me whether my boundary condition set up is ok or not according to the attached paper in this thread? OpenFoam 3.0.1. Any comment can be useful for me. Thanks in advance.

Hi!

I checked it and your BCs are seems to be valid, and i tried to reconstruct the case, but I was unable to find the proper outlet conditions (always got some noisy phenomena at the top of the outlet). I think they did something tricky at the outlet.
What about your results? It is totally different?

Quote:

Originally Posted by simrego (Post 719440)

Hi Simrego,

You are right. I am also finding some noise at the outlet. My results not much different from their result but it should be same. The flow configuration looks similar but when I go for streamline it looks different. I am not in my office. I will send you a picture of streamline when I am at my office. Anyways, Thank you very much for your response.

Cheers,
Razon