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gravity calculation in interDymFoam

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Old   September 13, 2013, 12:38
Default gravity calculation in interDymFoam
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Daniel Witte
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Hello,

I am using InterDymFoam for the Simulation of a stirred vessel. Looking at various threads in this forum, I am unsure about the implementation of gravity in this solver. The solver requires defining a static pressure p_rgh. Unless the interface is horizontal and does not move, the addtional pressure due to gravity is not contant, but depends on how the 2 fluids are distributed in the calculated area. So, the adder rho x g x h is not constant. If the interface is constant and horizontal, the correction would p_rgh = p + rho2 g h with h being the height difference to the interface for h < 0 and p_rgh = p + rho1 g h for h > 0. This is my understanding, correct me if I am wrong.

Since my mixer has a horizontal shaft, the interface has no defined position, but will depend on the forces that move it. Well, this is why I am using this solver. I wonder what InterDymFoam does to account for this because, I think, the definition of static pressure does not make much sense for a two phase system (as decribed in many books as a form of the Bernoulli equation.

To get it right, one would need to use the real pressure and add to all computed cells the gravity drag within the balance of forces. What would I need to correct the solver (if it is wrong) or is there an alternative solver that accounts for gravity correctly?

The correction would only add little complication to the solver since, unless for compressible fluids, the density of a cell does not depend on pressure, but on composition only.

Regards,

Daniel
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