[Martin Hegedus]

Continuation of http://www.cfd-online.com/Forums/ope...nvergence.html

I tried to converge the simpleFoam airfoild2D example to machine zero, or at least the tolerance (which I set to 1.0e-8 for all variables). I was successful until I got to zero degrees angle of attack. It failed for zero. Then I backed off a bit in regards to alpha (2.2036e-6 degrees) and was successful!!

Results Are:

Case 1, After 1000 iterations
U -> internalField uniform (26.000000 0.000001 0); = approx zero degrees,
smoothSolver: Solving for Ux, Initial residual = 1.00795e-08, Final residual = 5.50998e-11, No Iterations 2
smoothSolver: Solving for Uy, Initial residual = 8.04807e-09, Final residual = 8.04807e-09, No Iterations 0
GAMG: Solving for p, Initial residual = 1.03209e-07, Final residual = 1.00942e-08, No Iterations 1
time step continuity errors : sum local = 1.54372e-11, global = 7.48481e-19, cumulative = -1.77796e-14
smoothSolver: Solving for nuTilda, Initial residual = 9.11008e-09, Final residual = 9.11008e-09, No Iterations 0
ExecutionTime = 79.64 s ClockTime = 82 s

Case 2, After 1000 iterations
U -> internalField uniform (26.000000 0.000000 0); = 0 degrees, outlet = free stream
1000 iterations
smoothSolver: Solving for Ux, Initial residual = 5.60021e-05, Final residual = 3.20606e-06, No Iterations 2
smoothSolver: Solving for Uy, Initial residual = 3.15896e-05, Final residual = 1.81395e-06, No Iterations 4
GAMG: Solving for p, Initial residual = 0.000320099, Final residual = 3.03047e-05, No Iterations 7
time step continuity errors : sum local = 4.62797e-08, global = 1.18427e-17, cumulative = -3.77372e-15
smoothSolver: Solving for nuTilda, Initial residual = 2.10995e-06, Final residual = 4.48997e-08, No Iterations 2
ExecutionTime = 94.83 s ClockTime = 97 s

Anyone know what the story is? I gather there is a good chance it is some sort of a switch or bug. I can't believe I'm the first to experience this, so I guess it is a switch.

I'm using version 1.6 of OpenFOAM.