Density as function of pressure

sorrego · May 20, 2009, 16:08

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.

Rui · May 20, 2009, 16:42

So far, what have you tried to set the density as that function of the pressure?

sorrego · May 20, 2009, 19:04

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.
Santiago

Jules · May 20, 2009, 19:35

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]

Regards,
Jules

sorrego · May 21, 2009, 11:34

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

May 20, 2009, 16:08	Density as function of pressure	#1
sorrego New Member Santiago Orrego Join Date: Mar 2009 Posts: 9 Rep Power: 17	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.

May 20, 2009, 16:42		#2
Rui Member Rui Igreja Join Date: Mar 2009 Location: Aveiro Posts: 68 Blog Entries: 1 Rep Power: 17	So far, what have you tried to set the density as that function of the pressure? __________________ Rui

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May 20, 2009, 19:04		#3
sorrego New Member Santiago Orrego Join Date: Mar 2009 Posts: 9 Rep Power: 17	Hello. Thanks for reading. I try to create an expression called rho (and specify that expression in the Material propieties) rho= ((3e9+1.34p)/(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. Santiago

May 20, 2009, 19:35		#4
Jules Member Jules Bell Join Date: May 2009 Posts: 32 Rep Power: 17	3e9 has no dimension, but 1.34p has [Pa], that's why it doesn't work. -> try: ((3e9 [Pa] + 1.34p)/3e9 [Pa] + p)) * 860 [kg m^-3] Regards, Jules

May 21, 2009, 11:34		#5
sorrego New Member Santiago Orrego Join Date: Mar 2009 Posts: 9 Rep Power: 17	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] + 1.34p) / (5.9e8 [Pa] + p) ) 860 [kg m^-3] Bye! and thanks. Santiago