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modeling flow over terrain with buoyancy

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Old   January 26, 2010, 14:27
Default modeling flow over terrain with buoyancy
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To all the wind modelers:

I have been having problems including buoyancy for atmospheric stability considerations into my flow model.

I have a model which works well with icoFoam and rhoPimpleFoam for generic wind modeling purposes over complex terrain. However I wish to use the unsteady buoyantPisoFoam to include stability effects. I am certain that my problems have to do with BCs so my question is:

How to implement the buoyantPressure bc correctly for a case with an inlet to the left, outlet to the right, atmosphere on the top and terrain on the bottom with symmetry planes on the sides?

Any help would be much appreciated!
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Old   January 27, 2010, 12:41
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Scott Haynes
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stevek
It sounds as if we are working on the same general problem. Microscale modeling and using buoyantPisoFoam. I have had luck when initializing from a mesoscale model or in areas with more or less level terrain. I typically face challenges in sloped areas or gap flows where I am formulating boundary conditions based on on-site meteorological instrumentation. The solution in these situations seems to be to try everything until something gives you a reasonable result. With this in mind I can tell you that I have tried so many things that it's difficult to answer your question becasue everywhere seems to be a little different.

To start with I typically use some matlab scripts to generate BC that conserve momentum, enthalpy and mass such that the wind blows in the direction I want it to. You could do this a number of different ways I'm sure but the scripts I have evolved over time are not trivial. If you have a semi-working model right now that's blowing up why don't you post your error and let others take a look.

scott
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Old   February 3, 2010, 03:11
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Jiang
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Quote:
Originally Posted by stevek View Post
To all the wind modelers:

I have been having problems including buoyancy for atmospheric stability considerations into my flow model.

I have a model which works well with icoFoam and rhoPimpleFoam for generic wind modeling purposes over complex terrain. However I wish to use the unsteady buoyantPisoFoam to include stability effects. I am certain that my problems have to do with BCs so my question is:

How to implement the buoyantPressure bc correctly for a case with an inlet to the left, outlet to the right, atmosphere on the top and terrain on the bottom with symmetry planes on the sides?

Any help would be much appreciated!
Yes, stevek, may be we have the same problem, you could see:
buoyantBoussinesqPisoFoam: A detailed explanation
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Old   February 11, 2010, 04:45
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Hi Scott,

Thank you for the reply. My problems were in fact due to the unphysical specification of boundary and initial conditions from homemade velocity and temperature profiles. Using realistic profiles (from meso data) has solved the problem.

Cheers
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