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Pressure referencing in the rhoPimpleFoam solver?

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Old   September 23, 2019, 21:51
Default Pressure referencing in the rhoPimpleFoam solver?
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Ruiyan Chen
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Foamers,

As far as I understand, the rhoPimpleFoam solver solves the equation for absolute pressure, and it is considered to be a general compressible solver (or it can deal with variable density flows in a general way).

However, it adopts the conventional pressure-velocity coupling approach. That is, formulating a pressure equation from the continuity constraint instead of solving for the density directly. Why does it solve the absolute pressure instead of the dynamic pressure? I remember from my numerical class that it is a standard way of dealing with pressures to use a reference pressure and a dynamic one. The solver only solves for the dynamic pressure, which is very small compared to the reference pressure. I ask this question because if one wants to simulate a jet flow, e.g., a hot gas enters into a large cold ambient (so there's density variations), by using rhoPimpleFoam one needs to provide an absolute pressure (like 1atm) at the outlet. Problem is, in jet flow configurations, the pressure variation is normally like several hundred Pa, which is very small compared to 1atm. Most commercial solvers will ask you to specify a reference pressure (in this case, 1atm), and they solve only the dynamic pressure. By doing this the pressure gradients can be very accurate and this results in a better velocity prediction.

Am I missing some obvious things about this solver? Is it possible to let rhoPimpleFoam to solve only the dynamic pressure?

Thanks in advance,
Ruiyan
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