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Supercritical flow in a duct_pressure blowup at initial time step

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Old   March 7, 2017, 12:49
Default Supercritical flow in a duct_pressure blowup at initial time step
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Mahdi Nabil
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Hi everyone,

I am trying to simulate supercritical CO2 turbulent flow and heat transfer in a duct using buoyantPimpleFOAM. So far, I have been using const fluid properties and it was working fine.
Currently, I am using a new EOS in which rho and psi (compressiblity) are both functions of pressure and temperature (since we are in a supercritical region. In other words,
rho=rho(p,T)
psi=drho/dp = psi(p,T)
And, I am sure about the psi formulation and implementation in the code which is the exact analytical differentiation of rho wrt p. However, when I use psi(p,T) it makes the pressure to be unstable at the very first time step and the code blows up. I've printed the output:



diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
PIMPLE: iteration 1
DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 5.15665e-08, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 1, Final residual = 4.17258e-07, No Iterations 3
DILUPBiCG: Solving for Uz, Initial residual = 1, Final residual = 3.51138e-07, No Iterations 3
DILUPBiCG: Solving for h, Initial residual = 0.999991, Final residual = 1.05686e-07, No Iterations 4
GAMG: Solving for p_rgh, Initial residual = 0.999569, Final residual = 4.66604e+56, No Iterations 1000
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 123.314, global = -15.475, cumulative = -15.475
************************************************** ********
**** Max Pressure = 1.50284e+61 **** Min Pressure = -8.4671e+60
**** Max Temperature = 313.004 **** Min Temperature = 312.996
************************************************** ********


I have attached my p, T, and U boundary conditions in the 0 folder. Does anyone have any idea if I am making any mistake in the boundary conditions? These boundary conditions work perfectly for a constant psi value, but blows up the pressure for psi(p,T).

Thanks a lot in advance.
Attached Files
File Type: zip 0_P_U_T.zip (2.2 KB, 0 views)
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blowing up, boundary condition, buoyantpimplefoam, pressure, turbulent flow

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