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Old   April 4, 2005, 03:18
Default About divergence for help!
  #1
xhliu1
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Posts: n/a
Hello,everyone!

Now I have a problem about divergence.

When I do caculation of one case,it will divergence when I do it as tuebulent flow,while when I do it as laminar flow,it will not divergence.

The printfile on screen it as follows: *** GEOMETRICAL CALCULATIONS STARTED *** GEOMETRICAL CALCULATIONS COMPLETED

|----------------------------------------|

| STAR VERSION 3.150 |

| THERMOFLUIDS ANALYSIS CODE |

| Run on hardware: Linux |

| Stardate: 4-APR-2005 Time is 10:41:44 |

|----------------------------------------|

|-----------------------------------------------------------|

| STAR Copyright (C) 1988-2001, Computational Dynamics Ltd. |

| Proprietary data --- Unauthorized use, distribution, |

| or duplication is prohibited. All rights reserved. |

|-----------------------------------------------------------|

|-------------------------------------------------------------------------------------------|

| ---------------------------- PROBLEM SPECIFICATION SUMMARY ---------------------------- |

|-------------------------------------------------------------------------------------------|

| CASE TITLE .................. => |

| NUMBER OF CELLS ............. => 242512 |

| NUMBER OF BOUNDARY FACES .... => 39301 |

| MESH DIMENSIONS XMIN XMAX YMIN YMAX ZMIN ZMAX |

| (IN METRES) ............ => 0.0E+00 1.3E+00 0.0E+00 8.9E-01 0.0E+00 2.1E+00 |

| RESTART DATA ................ => WILL BE SAVED ON FILE.pst |

| SURFACE DATA ................ => WILL NOT BE SAVED |

| BOUNDARY DATA ............... => WILL NOT BE PRINTED |

| CONVERGENCE DATA ............ => WILL NOT BE PRINTED |

| FIELD DATA .................. => WILL NOT BE PRINTED |

| STEADY FLOW ................. => START FROM ITERATION = 0 |

| INITIALISATION .............. => WILL BE EMPLOYED |

| DATA DUMP (FILE.pst)......... => EVERY 10 ITERATIONS |

| SOLUTION PROCEDURE .......... => SIMPLE |

| RESIDUAL TOLERANCE .......... => 1.00E-03 |

| MAX. NO. OF ITERATIONS ...... => 100 |

| NO. OF FLUID MATERIALS ...... => 1 |

|-------------------------------------------------------------------------------------------|

|-> FLUID 1 -------------------------------------------------------------------|

|-------------------------------------------------------------------------------------------|

| SOLVE ....................... => U, V, W, P, TE, ED,VIS, |

| FLUID FLOW .................. => TURBULENT INCOMPRESSIBLE HIGH RE K-EPS MODEL |

| CHARACTERISTIC LENGTH ....... => 1.000E+00 m |

| MONITORING LOCATION ......... => 146468 |

| REFERENCE PRESSURE .......... => PREF = 1.000E+05 Pa |

| MOLECULAR VISCOSITY ......... => CONSTANT - MU = 1.810E-05 Pas |

| DENSITY ..................... => CONSTANT - RHO = 1.205E+00 kg/m3 |

| FIXED FLOW BOUNDARY FLUXES... => FVIN = 0.000E+00 kg/s FVOUT = 1.929E-01 kg/s |

| => FLOUT = 0.000E+00 kg/s |

|-------------------------------------------------------------------------------------------|

|-> BOUNDARY TYPES USED -------------------------------------------------------------------|

|-------------------------------------------------------------------------------------------|

| INLET, WALL, PRESSURE, |

| Turbulence intensity and Mixing length specified at inlets |

| Turbulence intensity and Mixing length specified at pressure boundaries |

|-------------------------------------------------------------------------------------------|

|-> SOLUTION PARAMETERS -------------------------------------------------------------------|

|-------------------------------------------------------------------------------------------|

| VARIABLE | U V W P TE ED |

|-------------------------------------------------------------------------------------------|

| RELA. FAC. | 7.000E-01 7.000E-01 7.000E-01 3.000E-01 7.000E-01 7.000E-01 |

| DIFF. SCH. | UD UD UD - UD UD |

| DSCH. FAC. | 0.000E+00 0.000E+00 0.000E+00 - 0.000E+00 0.000E+00 |

| SOLV. TOL. | 1.000E-01 1.000E-01 1.000E-01 5.000E-02 1.000E-01 1.000E-01 |

| SWEEP LIM. | 100 100 100 1000 100 100 |

|-------------------------------------------------------------------------------------------|

| VARIABLE | T DENS TVIS MVIS CP COND |

|-------------------------------------------------------------------------------------------|

| RELA. FAC. | 9.500E-01 1.000E+00 1.000E+00 1.000E+00 1.000E+00 1.000E+00 |

| DIFF. SCH. | UD CD - |

| DSCH. FAC. | 0.000E+00 1.000E-02 - - - - |

| SOLV. TOL. | 1.000E-01 - - - - - |

| SWEEP LIM. | 100 - - - - - |

|-------------------------------------------------------------------------------------------|

| * RESIDUAL NORMALISATION PRACTICE REPRESENTATIVE OF VARIABLE FLUX USED |

| * NORMALISATION FACTORS WILL BE DYNAMICALLY UPDATED AS THE FLOW DEVELOPS |

|-------------------------------------------------------------------------------------------|

|------------------------------------| I---------------------------------------------| CALCULATION MONITORING INFORMATION |---------------------------------------------I

|------------------------------------|

ITER I---------------- GLOBAL ABSOLUTE RESIDUAL ----------------I I----------- FIELD VALUES AT MONITORING LOCATION -------I

NO UMOM VMOM WMOM MASS T EN DISS ENTH U V W P TE ED T

1 3.83E-02 3.05E-02 1.04E-02 1.00E+00 9.45E-02 NaN 0.00E+00 -8.49E-02 1.22E-01-4.91E-03-1.33E-01 7.40E-04 2.10E-07 2.00E+01 &&&& -------------------------------------------------------------- --------------------------------------------------------------

*** SOLUTION DIVERGES/UNSTABLE.

*** CALCULATIONS TERMINATED; NEW FILE.div WRITTEN

STAR-CD Version 3.150 Computational Dynamics, Ltd. END OF EXECUTION - STAR CPU TIME IS 47.77 ELAPSED TIME IS 147.71

__________________________________________________ _____

I am waiting for hopes!! Thank you very much!
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Old   April 6, 2005, 07:14
Default Re: About divergence for help!
  #2
allan
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Hi appears to be diverging on epsilon. Reduce you turbulence intensity an length scale by an order of magnitude and see if it runs. If so you've probably specified unrealistic turbulence parameters.

allan
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Old   April 7, 2005, 03:53
Default Re: About divergence for help!
  #3
xhliu1
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Allan,Thank you for your reply! I have checked the model again,and found that I have set the turbulence model error,that is I have set the parameter of Cmu as User,acturaly,it should be as valuabe 0.09.

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