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a question about icoFoam equations

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Old   July 2, 2013, 06:15
Default a question about icoFoam equations
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Yu CAO
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Hi
I found that the pressure term in the momentum equation in icoFoam does not divided by the denssity rho. Isn't it magnified the speed U by rho times in this way? Any one who could tell the reason? Thanks.
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Old   July 2, 2013, 14:16
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Mohsen KiaMansouri
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Dear Yu
If you open the p in icoFoam/cavity/0/p you can see that:
Code:
dimensions      [0 2 -2 0 0 0 0];
which is the dimension for p/rho. it means that for incompressible solvers the p equals to kinematic pressure p/rho.
but it differs for compressible solvers for example if you see the tutorials/compressible/rhoPimpleFoam/ras/cavity/0/p
you can see that:
Code:
dimensions      [1 -1 -2 0 0 0 0];
which is the correct dimension that you want!
So in conclusion,p differs in compressible & incompressible solvers.
Good Luck
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Old   July 2, 2013, 14:47
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Quote:
Originally Posted by cfdonline2mohsen View Post
Dear Yu
If you open the p in icoFoam/cavity/0/p you can see that:
Code:
dimensions      [0 2 -2 0 0 0 0];
which is the dimension for p/rho. it means that for incompressible solvers the p equals to kinematic pressure p/rho.
but it differs for compressible solvers for example if you see the tutorials/compressible/rhoPimpleFoam/ras/cavity/0/p
you can see that:
Code:
dimensions      [1 -1 -2 0 0 0 0];
which is the correct dimension that you want!
So in conclusion,p differs in compressible & incompressible solvers.
Good Luck
Thank you. I have noticed this. However, I am wondering if the result would be the same when I use these two ways. I mean, if in the p file, there are only two boundary conditions, fixedvalue zero and zerogradience. and the result of solving equation with rho and without the rho would be the same. In other words, would boundary conditions fixedvalue zero and zerogradience would stay unchanged in both p and p/rho files. the only change would only be the dimension in this way. Thank you.
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