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Incorrect mass equation, ansys is still converging?

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Old   January 7, 2014, 06:34
Default Incorrect mass equation, ansys is still converging?
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Hello all

atm im trying to simulate a water bath in which a specific mass flow enters through a injecting pipe (as you can see in the attached picture). While I was playing around with the boundary conditions, i realized that as far as I can estimate the conservation of mass in my bath is not given. As there are no openings and no outlets and the income mass flow is positive, I expected the solver to diverge. But still I got results.

Due to I am new to ansys and cfx, i am wondering if there are any mistakes in meshing or the setup.

Thanks in advance

Pete

Setup.jpg

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Old   January 8, 2014, 11:12
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I would be very thankful for any help
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Old   January 8, 2014, 17:09
Default pressure? temperature?
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Hello,
I'm also quite new to CFX but more or less experienced in all other ANSYS stuff which helps to understand what other simulation packages are like. So I'm sure that conservation of mass isn't the only target to watch. I have in mind the important equation: p*V = const * n*T (static, for ideal gases though; something similar for fluids in statics)
So if n is increasing (forced mass flow in and nothing out --> no mass conservation at all) and volume is constant (rigid walls, no fluid-structure-interaction) and no phase change and of course a scientific constant, there are 2 other dregrees of freedom. And don't forget: in many cases as long as there is no numerical problem, the solver solves the equations, whether physically reasonable or not, e.g. water pressure may heavily increase, in contrast what we "postulate" in general: it's some kind of incompressible.
Did you examine pressure and temperature?

An example from electromagnetics:
In ANSYS one may define a relative permeability of almost zero in some material, which gives an "magnetic insulator". ANSYS solves Maxwell's equations without any (convergence) problems, but no such material exists.

HLo

Last edited by HLo; January 9, 2014 at 03:14.
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Old   January 12, 2014, 07:24
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Hi muellmann,

Can you post your CCL? Thanks.
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