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Old   January 16, 2012, 12:27
Default Presure results squareBend
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Pierre Castellani
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Hi,
I've run the squareBend tutorial with several added calculations. I get the following results:
Time = 500

GAMG: Solving for Ux, Initial residual = 0.00114342, Final residual = 0.000104067, No Iterations 4
GAMG: Solving for Uy, Initial residual = 0.000728807, Final residual = 6.92936e-05, No Iterations 3
GAMG: Solving for Uz, Initial residual = 0.0426736, Final residual = 0.00411956, No Iterations 3
GAMG: Solving for p, Initial residual = 0.00292189, Final residual = 0.000205264, No Iterations 3
time step continuity errors : sum local = 1.16781, global = -0.115124, cumulative = -125.995
rho max/min : 0.507862 0.233955
GAMG: Solving for h, Initial residual = 0.00161684, Final residual = 0.000140944, No Iterations 4
ExecutionTime = 179.84 s ClockTime = 181 s

Averages of T : inlet = 1000 outlet = 970.329
Averages of p : inlet = 122930 outlet = 110000
Averages of U : inlet = (468.057 0 0) outlet = (-445.63 0.441477 0.762627)
MassFlows: inlet = -0.439657 outlet = 0.439453

Going back to basics I ve tried to apply some simple formula p=r*rho*T then mass=rho*U*Area (don't be affraid it is just to get an idea ;-) ).
Applying this to outlet gives us rho=0.395 and mout=0.4399 which is very close to the one calculated by openFoam. Doing the same for the inlet is a bit strange rho=0.428 and min=0.501, which is quite far from the calculated one.

I will be very glad to understand my mystake, if you could help me thanks a lot.
Pierre.
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Old   January 17, 2012, 12:08
Default Please help
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Pierre Castellani
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So, going a bit further (which are quite cool by the way) I get the following results:
Time = 500

GAMG: Solving for Ux, Initial residual = 7.85017e-09, Final residual = 7.85017e-09, No Iterations 0
GAMG: Solving for Uy, Initial residual = 6.48846e-09, Final residual = 6.48846e-09, No Iterations 0
GAMG: Solving for Uz, Initial residual = 1.30316e-08, Final residual = 5.26334e-09, No Iterations 1
GAMG: Solving for p, Initial residual = 1.64444e-08, Final residual = 2.91877e-09, No Iterations 1
time step continuity errors : sum local = 1.43382e-05, global = 9.50578e-08, cumulative = -375.781
rho max/min : 0.535971 0.305706
GAMG: Solving for h, Initial residual = 8.82731e-09, Final residual = 8.82731e-09, No Iterations 0
GAMG: Solving for epsilon, Initial residual = 1.00608e-08, Final residual = 2.54175e-09, No Iterations 1
GAMG: Solving for k, Initial residual = 1.66265e-08, Final residual = 3.90612e-09, No Iterations 1
ExecutionTime = 188.73 s ClockTime = 189 s

Averages of T : inlet = 1000 outlet = 952.305
Averages of p : inlet = 129606 outlet = 110000
Averages of rho : inlet = 0.450494 outlet = 0.401513
Averages of k : inlet = 739.142 outlet = 1171.94
Averages of epsilon : inlet = 660407 outlet = 4.58901e+06
Averages of U : inlet = (443.962 0 0) outlet = (-432.941 0.798248 -3.89557e-08)
Integrals of U : inlet = (1.10991 0 0) outlet = (-1.08235 0.00199562 -9.73893e-11)
MassFlows: inlet = -0.434892 outlet = 0.434892
End

The rho calculation is equal du mine ==> looks good.
The integral of U which is just Ui*Ai gives the same results than mine==> good.
So finally I don't understand the calculation of MassFlows inlet!! Of course it is wired to have the inlet mass greater than the outlet mass where is the missing mass? Which calculation is wrong?
The last assumption is that using:
inlet
{
type flowRateInletVelocity;
flowRate 0.5; //0.75;
value uniform (0 0 0);
}
the normal vector is not always on the same direction, but in this case the inlet face is very simple!
Help will be very appreciate.
Thanks,
pierre.
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