# Pressure Inlet yields wrong velocities

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 November 21, 2004, 02:47 Pressure Inlet yields wrong velocities #1 Ben Guest   Posts: n/a Sponsored Links Hello, I am using Fluent 6 to simulate the supersonic air flow in a 2d tube. I am using a pressure inlet and pressure outlet. I know what the static pressure and total pressure is at the inlet, along with total temperature. ptot = 80 psi pstatic = 12 psi Ttot = 600 K Therefore I have a pressure ratio of .15 using Isentropic tables this gives me a Mach number of M =1.9 and a velocity of 779 m/s For the Pressure inlet BC: I set the Total gauge pressure equal to the ptot-p_operating I set the supersonic/inital gauge pressure = to pstatic-poperating For the Pressure Outlet BC: I set the gauge pressure to the gauge pressure of the of the inlet. But this shouldn't matter since it is all supersonic flow The problem is that fluent computes a velocity at the inlet that is at least too large by a factor of 2! Any ideas what could be going wrong here? I am using an "operating pressure" of 0.1 psi, because if I set it to zero I get a "floating point error." I am using the segregated solver, but even if I use the coupled solver I get similar results. Thanks for your help in advance, Ben

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