# convergence issues on steady state solver

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 March 28, 2011, 21:20 convergence issues on steady state solver #1 Member   iswadi Join Date: Feb 2010 Posts: 44 Rep Power: 16 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 THERMAL RADIATION MODEL: 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 ADVECTION SCHEME: 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

 March 30, 2011, 19:11 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,748 Rep Power: 143

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