# thermo settings for natural and forced convection

 Register Blogs Members List Search Today's Posts Mark Forums Read

 April 24, 2011, 14:07 thermo settings for natural and forced convection #1 Senior Member   Fabian Braennstroem Join Date: Mar 2009 Posts: 407 Rep Power: 10 Hi, I am still having a bit trouble understanding the thermoPhysicalProperties settings. I mainly have two different challenges, a natural convection, for which I am using buoyantSimpleFoam and a forced convection at Ma-number around 0.4, for which I plan to use rhoSimpleFoam (or buoyantSimpleFoam as well?). For the solvers hRhoThermo and hPsiThermo are used; as far as I know this means, that: - hPsiThermo (buoyantSimpleFoam), calculation based on enthalpy 'h' and compressibility 'psi' - hRhoThermo (rhoSimpleFoam), calculation based on enthalpy or sensible enthalpy What is the reason (maybe numerically!?) to have different thermo models for these kind of problems? Even more confusing for me is that the buoyantPimpleFoam solver is based hRhoThermo... why should it be different to buoyantSimpleFoam!? Thanks in advance! Fabian

 April 26, 2011, 03:54 #2 Senior Member   Christian Lucas Join Date: Aug 2009 Location: Braunschweig, Germany Posts: 198 Rep Power: 8 Hi Fabian, both hPsiThermo and hRhoThermo more or less do the same. In hPsiThermo, the density is calculate by rho=psi*p with psi=1/(RT). In hRhoThermo, the density is calculated (assuming you use a perfect gas) rho=p/(RT). The main advantage of hPsiThermo is that the pressure correction of the density (see solver) is very simple because psi is a constant (for perfect gases). The main disadvantage is that the equation already assumes perfect gas behavior. So, the reason (as I understand it) of hRhoThermo is to avoid this disadvantage and to make it possible to use other equation of state like the polynomial by introducing an internal rho field in the thermo library. Regards, Christian

 April 27, 2011, 14:55 #3 Senior Member   Fabian Braennstroem Join Date: Mar 2009 Posts: 407 Rep Power: 10 Hi Christian, thanks for your help! This would mean, that if I expect a perfect gas the hPsi approach would be more stable from the numerics point of view!? Regards! Fabian

 May 1, 2011, 12:33 #4 Senior Member   Christian Lucas Join Date: Aug 2009 Location: Braunschweig, Germany Posts: 198 Rep Power: 8 Hi, no, it wouldn't be more stable (if you code it correctly), but it would be faster ( assuming you code to correctly). Regards, Christian

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Alex CD-adapco 5 December 12, 2007 05:58 lucia FLUENT 3 September 7, 2007 16:59 Daniele Main CFD Forum 0 December 20, 2005 09:09 Jan Main CFD Forum 4 November 30, 2005 23:44 Venu Gopal FLUENT 0 August 29, 2004 10:59

All times are GMT -4. The time now is 05:01.