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Old   May 20, 2009, 16:08
Default Density as function of pressure
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Santiago Orrego
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Hello Guys.
Im making a steady simulation of a oil film. I need to establish the Density as function of pressure.

rho=rho_initial*( (c1 + c2 * Pressure ) / ( c1 + Pressure ) )

Can anybody can please help me to establish that to the solver?


Thanks a lot.
Santiago.
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Old   May 20, 2009, 16:42
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Rui Igreja
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So far, what have you tried to set the density as that function of the pressure?
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Old   May 20, 2009, 19:04
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Santiago Orrego
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Hello. Thanks for reading.

I try to create an expression called rho (and specify that expression in the Material propieties)

rho= ((3e9+1.34*p)/(3e9+p)) * 860 [kg m^-3]

But the solver said that the dimension are wrong. I tried several combinations of the dimensions and not succeded.

Any ideas??

Thanks.
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Old   May 20, 2009, 19:35
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Jules Bell
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3e9 has no dimension, but 1.34*p has [Pa], that's why it doesn't work.
-> try: ((3e9 [Pa] + 1.34*p)/3e9 [Pa] + p)) * 860 [kg m^-3]

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Old   May 21, 2009, 11:34
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Santiago Orrego
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Thanks Jules.

It worked. I tryied that once, but the my mistake was that I was putting [pa] and not [Pa].

So. it finally worked using:

((5.9e8 [Pa] + 1.34*p) / (5.9e8 [Pa] + p) ) * 860 [kg m^-3]

Bye! and thanks.

Santiago
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