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Old   August 22, 2006, 23:45
Default Hi all, I have been working
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Shaun Cooper
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Hi all,

I have been working with openFOAM for a little while now but I am still having trouble creating the model I would like. I am able to create the mesh and the initial fields but I am not able to get the model to solve. Essentially I have two fluids; one that occupies the entire domain (a 3D rectangular Prism) whilst the other flows through the domain, with the shape of a tube. There are 3 equations that I would like to include: the continuity equation, a momentum equation and a temperature equation. I would like to solve for density (or pressure), Velocity and Temperature.

The momentum equation has the following terms:

Lagragian Derivative of U - gravity - viscosity (laplacian of U) + iondrag (difference of the two fluid velocities) = pressure gradient.

The temperature equation has the following:

Lagrangian Derivative of T + conductive heating term (Laplacian of T) + work term (T times divergence of U) = time rate of change of kinetic energy (time derivative of kinetic energy equation (.5mv^2)).

Is it possible to model such a problem with openFOAM. If so, which tutorial solver is the closest maatch for this model, ie which solver should I begin with and 'hack' into the solver I require.

If someone is able to help but needs more information on the problem let me know and I can email the details.

Thanks in advance,

Shaun
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Old   August 23, 2006, 05:56
Default That depends on how the 2 flui
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Eugene de Villiers
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That depends on how the 2 fluids are coupled.
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Old   August 23, 2006, 18:48
Default Thanks for the response Eugene
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Shaun Cooper
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Thanks for the response Eugene,

There is simply a one-way coupling. The fluid that occupies the entire domain is affected by the fluid that flow in a 'tube'. The fluid that flows in the 'tube' is not effected by anything.

Do you think this sort of problem could be model in openFOAM?

I started working with sonicTurbFoam but the turbulence part of the model is not important to us. Also, with this solver, adjusted a little to suit the equations I need, give solution singularities for pressure, which of course leads to all other fields having either solution singularities or NANs.

Thanks

Shaun
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Old   August 24, 2006, 04:37
Default Unless your flow is hypersonic
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Eugene de Villiers
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Unless your flow is hypersonic, I would use rhoTurbFoam as a starting point, not a sonic code.

How do you accomplish the coupling at present?
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Old   August 24, 2006, 04:42
Default Sorry, I meant to say "transon
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Sorry, I meant to say "transonic"
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Old   August 24, 2006, 22:57
Default Hi Eugene The flows will al
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Shaun Cooper
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Hi Eugene

The flows will all be subsonic. Also, we are not interested in the turbulence associated with the flows. Does it make the model more stable to include the k-epsilon turbulence model? At the moment the coupling between the two fluids in the momentum equation is achieved from a term that consists of the difference between the to velocity fields (multiplied by a collisional frequency co-efficient). In the energy equation the coupling is of the same form expect the velocity difference is squared here.

Thanks for your interest and assistance,

Shaun
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Old   August 27, 2006, 21:11
Default I meant to say that the energy
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I meant to say that the energy equation is coupled in the same way as the momentum equation EXCEPT the velocity difference is squared.

Shaun
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