# Incompressible Ideal gas law

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 February 19, 2009, 09:05 Incompressible Ideal gas law #1 Leverkin Guest   Posts: n/a Hello dear people, I would like to ask about the incompressible ideal gas law. As i have understood, and please correct me if I am mistaken, when you use the incompressible ideal gas law the fluid is incompressible due to the low mach number but depends from the temperature variations. What happens then to the density in the continuity equation? Is it still removed from the equation (because it is incompressible) and it is grad(V) = 0? or Fluent solves grad(ρV) = 0 and it is taking account of the density variations from the temperature? Thanks in advance marrianne likes this.

 February 20, 2009, 06:51 Re: Incompressible Ideal gas law #2 Suresh kumar Guest   Posts: n/a It solves grad(ρV) = 0 and it is taking account of the density variations from the temperature by calculating gas equation.In transient cases, time also plays role.

 February 20, 2009, 09:54 Re: Incompressible Ideal gas law #3 Leverkin Guest   Posts: n/a Thank you very much for your reply. So the name "incompressible" is not accurate since it's solving grad(ρV)=0. Again thank you for your reply. Best.

 February 23, 2009, 05:52 Re: Incompressible Ideal gas law #4 Ralf Schmidt Guest   Posts: n/a the fluid is incompressible, because it can not be compressed by pressure. So density depends only on temperature Ralf

 March 3, 2009, 10:57 Re: Incompressible Ideal gas law #5 Leverkin Guest   Posts: n/a Yes i agree with you. But the term incompressible is used only if we solve grad(u)=0. Since we don't solve grad(u)=0, and we solve grad(ρu)=0, then the fluid is compressible careless of what the density depends on, pressure or temperature. I am just trying to understand what Fluent solves for. Thank you for your reply.

 March 5, 2009, 17:41 Re: Incompressible Ideal gas law #6 Leverkin Guest   Posts: n/a I keep doing the same error. It is not grad(ρu)=0. It's div(ρu)=0. Sorry for this mistake but I don't use this notation at all!

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