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Old   September 4, 2008, 07:41
Default Hallo, I'm trying to simula
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Chris
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Hallo,

I'm trying to simulate multiphase flow in t-junction.
Boundary conditions are:
inlet1 – water – freestream
inlet2 – other liquid (properties similar to water) – freestream
outlet – atmosphere
channel walls – wall

mesh contains about 125000 elements. I have used checkMesh and mesh is OK.
Could you please have a look on this piece of convergence history:

Starting time loop

Courant Number mean: 8.22783e-05 max: 0.023297
Time = 0.00507

MULES: Solving for gamma
Liquid phase volume fraction = 9.07245e-05 Min(gamma) = -2.57618e-82 Max(gamma) = 1
MULES: Solving for gamma
Liquid phase volume fraction = 9.11763e-05 Min(gamma) = -2.57553e-82 Max(gamma) = 1
DICPCG: Solving for pd, Initial residual = 0.00924923, Final residual = 0.00085711, No Iterations 1001
time step continuity errors : sum local = 1.49501e-09, global = 6.28848e-11, cumulative = -7.2917e-07
ExecutionTime = 7378.93 s ClockTime = 7413 s

Courant Number mean: 8.21685e-05 max: 0.0232836
Time = 0.00508

MULES: Solving for gamma
Liquid phase volume fraction = 9.16281e-05 Min(gamma) = -2.57488e-82 Max(gamma) = 1
MULES: Solving for gamma
Liquid phase volume fraction = 9.20799e-05 Min(gamma) = -2.57423e-82 Max(gamma) = 1
DICPCG: Solving for pd, Initial residual = 0.0062962, Final residual = 0.000132535, No Iterations 1001
time step continuity errors : sum local = 2.3038e-10, global = -3.58816e-12, cumulative = -7.29174e-07
ExecutionTime = 7395.18 s ClockTime = 7429 s

I can't understand why from the very beginning it makes 1000 iterations about pressure equation within each timestep.
Thought it's a matter of timestep so I've switched on adjustment. After that courrant number was oscillated about 0.5 but number of pressure iterations hasn't changed.
I've red on this forum that wrong boundary conditions might be a reason of such big number of iterations. I've checked different boundary settings and used GAMG solver but nothing has changed.

As long as I'm obtaining reasonable results it doesn't bother me very much but I would like to speed up my simulation. Now, after 24hours simulation has passed 0.8s of total time. total time is 30s so it looks that I need to wait about month until it's finished

Do you have any suggestions. thank you for help in advance!!!
Chris
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