# How Does Operating Conditions Effect?

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 March 23, 2016, 10:59 How Does Operating Conditions Effect? #1 New Member   Join Date: Oct 2015 Posts: 24 Rep Power: 7 Hello all. In any case how does operating boussiesq temperature and operating density effect solution? I mean, what does happen if only operating conditions different between same cases? regards.

 March 23, 2016, 15:53 #2 Senior Member   Lucky Tran Join Date: Apr 2011 Location: Orlando, FL USA Posts: 4,119 Rep Power: 50 The difference between two simulations run with different operating temperature (and operating density) is the density itself. With the boussinesq approximation, the density is assumed constant (the operating density). If you change the operating temperature you change this density, which may affect your flow field. In other words, if you imagine you are running a constant density simulation and then change the density, this is the same effect as you would have if you changed the operating density in a simulation using the boussinesq model. This doesn't change the nominal buoyancy force but you can have a different heat capacitance which can affect the temperature field also and that indirectly affects the buoyancy force. Essentially, you have a different Reynolds/Rayleigh and Grashof numbers because of the different density.

March 23, 2016, 16:13
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 Originally Posted by LuckyTran The difference between two simulations run with different operating temperature (and operating density) is the density itself. With the boussinesq approximation, the density is assumed constant (the operating density). If you change the operating temperature you change this density, which may affect your flow field. In other words, if you imagine you are running a constant density simulation and then change the density, this is the same effect as you would have if you changed the operating density in a simulation using the boussinesq model. This doesn't change the nominal buoyancy force but you can have a different heat capacitance which can affect the temperature field also and that indirectly affects the buoyancy force. Essentially, you have a different Reynolds/Rayleigh and Grashof numbers because of the different density.
Then, if I use ideal gas model or polynomial constants for my case, different operating conditions does not effect my solution? They behave like something starting point? Am I right?

Regards.