
[Sponsors] 
Constant properties water with variable density as a function of temperature 

LinkBack  Thread Tools  Search this Thread  Display Modes 
October 30, 2014, 17:10 
Constant properties water with variable density as a function of temperature

#1 
Senior Member
Mr CFD
Join Date: Jun 2012
Location: Britain
Posts: 361
Rep Power: 15 
Hi,
In the material properties for water is it possible to use constant properties for everything except density? I want density to be a function of temperature and pressure. I've read that the Redlich Kwong real gas model may be able to do this. However if I turn it on, is it as difficult to converge with as full IAPWS (where every property is a function of pressure and temperature)? Thank you 

October 30, 2014, 19:30 

#2 
New Member
Ali Madayen
Join Date: Apr 2014
Posts: 22
Rep Power: 12 
Hi. Sorry but I can't get the problem right.
Isn't it possible by a simple expression? or there is something that makes it more complicated? 

October 31, 2014, 04:16 

#3 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,786
Rep Power: 143 
Yes, you can use constant properties except for density. What density equation of state do you want to apply?


October 31, 2014, 04:47 

#4 
Senior Member
Mr CFD
Join Date: Jun 2012
Location: Britain
Posts: 361
Rep Power: 15 
I have an EulerianEulerian free surface setup. I am modelling water liquid and water vapour, separated by a free surface.
I would like to apply variable density for the water liquid equation of state. So far I am modelling variable density in the water vapour phase as an ideal gas assumption. I've just stumbled across a fourth order polynomial expression of density as a function of temperature for the water liquid phase, which I may implement. This is the equation: Density [kg/m^3] = (2.98043*10^8*T^4)+(4.93093*10^5*T^3)+(3.25853*10^2*T^2)+(9.18937*T)+82.2757 Obviously to use the above expression you would need to call upon a dimensionless temperature (just divided T by 1 [K]) to give the correct units of density [kg/m^3]. Bar this approach, are there any others which would give me variable density for water liquid, but constant properties for everything else? 

November 1, 2014, 04:43 

#5 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,786
Rep Power: 143 
Rather than generate a dimensionless temperature use the correct units in your function. For instance:
Density = (2.98043*10^8 [kg m^3 K^4]*T^4)+(4.93093*10^5[kg m^3 K^3]*T^3)+(3.25853*10^2[kg m^3 K^2]*T^2)+(9.18937[kg m^3 K]*T)+82.2757 [kg/m^3] If you wanted variable density but constant everything else and you know this equation is the density versus temperature function then I would just use this, rather than trying to use the more sophisticated models. 

Thread Tools  Search this Thread 
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
[swak4Foam] installation problem with version 0.2.3  Claudio87  OpenFOAM Community Contributions  9  May 8, 2013 10:20 
Compile problem  ivanyao  OpenFOAM Running, Solving & CFD  1  October 12, 2012 09:31 
[blockMesh] error message with modeling a cube with a hold at the center  hsingtzu  OpenFOAM Meshing & Mesh Conversion  2  March 14, 2012 09:56 
[blockMesh] BlockMesh FOAM warning  gaottino  OpenFOAM Meshing & Mesh Conversion  7  July 19, 2010 14:11 
Warning 097  AB  Siemens  6  November 15, 2004 04:41 