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 icemaniac178 March 28, 2011 21:20

convergence issues on steady state solver

i`m new to cfx. i have a converged solution on my course mesh (0.9M elements). however i am having a problem to get a convergence to my steady state solver in a finer mesh (1.2M elements) . i have already go through all the manual and help file that provide in this forum but i still cannot meet the loose convergence criteria (RMS < 1x10-4). i have started by fine tuning the mesh, use increase and decrease of auto timescale, physical time scale and local time scale factor but the residual remains above the 1x10-4 even my iteration have reached about 1500. however i have put lift and drag coefficient as my monitor point and it shows almost constant value after 300-400 iteration. so i suspected, it maybe because of my BC. i would appreciate if somebody can give me some comments and suggestions on my BC as stated below. A part from of RMS residual variable what other value should i monitor in solver manager as guide towards convergence?

DOMAIN: Fluid
Coord Frame = Coord 0
Domain Type = Fluid
Location = B82
BOUNDARY: Airfoil
Boundary Type = WALL
Location = Airfoil
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
END
BOUNDARY: Fluid Default
Boundary Type = WALL
Location = F83.82,F85.82,F86.82
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Free Slip Wall
END
END
END
BOUNDARY: Inlet
Boundary Type = INLET
Location = Inlet
BOUNDARY CONDITIONS:
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Option = Cartesian Velocity Components
U = Ux
V = Uy
W = 0 [m s^-1]
END
TURBULENCE:
Fractional Intensity = 0.01
Option = Intensity and Auto Compute Length
END
END
END
BOUNDARY: Outlet
Boundary Type = OUTLET
Location = Outlet
BOUNDARY CONDITIONS:
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Option = Static Pressure
Relative Pressure = 0 [Pa]
END
END
END
BOUNDARY: Symmetry
Boundary Type = SYMMETRY
Location = Symmetry
END
DOMAIN MODELS:
BUOYANCY MODEL:
Option = Non Buoyant
END
DOMAIN MOTION:
Option = Stationary
END
MESH DEFORMATION:
Option = None
END
REFERENCE PRESSURE:
Reference Pressure = 1 [atm]
END
END
FLUID DEFINITION: Fluid 1
Material = Air at 25 C
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
HEAT TRANSFER MODEL:
Fluid Temperature = 25 [C]
Option = Isothermal
END
Option = None
END
TURBULENCE MODEL:
Option = SST
END
TURBULENT WALL FUNCTIONS:
Option = Automatic
END
END
END
OUTPUT CONTROL:
MONITOR OBJECTS:
MONITOR BALANCES:
Option = Full
END
MONITOR FORCES:
Option = Full
END
MONITOR PARTICLES:
Option = Full
END
MONITOR POINT: CD
Expression Value = cD
Option = Expression
END
MONITOR POINT: CL
Expression Value = cL
Option = Expression
END
MONITOR RESIDUALS:
Option = Full
END
MONITOR TOTALS:
Option = Full
END
END
RESULTS:
File Compression Level = Default
Option = Standard
END
END
SOLVER CONTROL:
Turbulence Numerics = First Order
Option = High Resolution
END
CONVERGENCE CONTROL:
Local Timescale Factor = 0.01
Maximum Number of Iterations = 1000
Minimum Number of Iterations = 1
Timescale Control = Local Timescale Factor
END
CONVERGENCE CRITERIA:
Residual Target = 1e-04
Residual Type = RMS

 ghorrocks March 30, 2011 19:11

http://www.cfd-online.com/Wiki/Ansys...gence_criteria

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