# reference pressure in Numeca

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 July 26, 2021, 06:58 reference pressure in Numeca #1 New Member   wwcs Join Date: May 2021 Posts: 4 Rep Power: 3 Hey, guys. I'm learning Numeca recently. I have a question about the reference pressure in Numeca. What is the meaning of it? If the reference pressure is 1atm, and the inlet total pressure is 2atm. Should I set the inlet total pressure to be 1atm (2atm-1atm) or 2atm?

 July 28, 2021, 13:48 #2 Senior Member   Hamid Zoka Join Date: Nov 2009 Posts: 277 Rep Power: 17 Hi; In NUMECA Boundary values for pressure are absolute values and do not need to be expressed with respect to reference pressure. The function of the mentioned reference pressure,together with reference temperature, is to calculate entropy and its value does not affect the results. As it is known, entropy is always measured with respect to a reference value and in thermodynamic processes its delta is important. So, These reference parameters can take any value. Regards

July 29, 2021, 08:51
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wwcs
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 Originally Posted by Hamidzoka Hi; In NUMECA Boundary values for pressure are absolute values and do not need to be expressed with respect to reference pressure. The function of the mentioned reference pressure,together with reference temperature, is to calculate entropy and its value does not affect the results. As it is known, entropy is always measured with respect to a reference value and in thermodynamic processes its delta is important. So, These reference parameters can take any value. Regards
Thank you!

 August 2, 2021, 04:06 #4 Senior Member   Colinda Join Date: May 2012 Location: Brussels Posts: 144 Rep Power: 12 I would like to add that apart from the entropy, the reference pressure is used at other places as well. This may be different for each solver. For example for the Fine™/Turbo solver this may be: in the Boussinesq approximation for incompressible fluid, in the outlet boundary condition for which the mass flow is imposed with pressure adaptation when the expert parameter MASPAO < 2, in the definition of the heat transfer coefficient when the expert parameter HTCDEF is set to 2. It is also used as a default gauge pressure for the preconditioning in case of low speed or incompressible flows. Hamidzoka likes this.