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An error has occurred in cfx5solve:Hi CFX users,
I am doing a transient simulation on stratified environment. I did lots of trial to fix my simulation but it was stopped in the middle of run and showed error. I understand it may be numerical unstability but i modified my mesh area, discretization scheme etc but I can't overcome the problem. First after 100 time step CFX solver was stopped then it was stoped after 500 time when I modified finally it was stopped after 2500 time step after my third modification in mesh and descritization scheme. Could any body help me to figure out the problem. I get the following message when CFX solver was stopped : An error has occurred in cfx5solve: | | | | The ANSYS CFX solver exited with return code 1. No results file | | has been created. End of solution stage. +--------------------------------------------------------------------+ | The following transient and backup files written by the ANSYS CFX | | solver have been saved in the directory | | G:/Re200Fr1-5_2740_Working/dp0/CFX-5/CFX/Work1/Fluid Flow CFX_002: | | | | 996.trn, 983.trn, 97.trn, 969.trn, 955.trn, 941.trn, 927.trn, | | 913.trn, 900.trn, 886.trn, 872.trn, 858.trn, 844.trn, 830.trn, | | 83.trn, 816.trn, 803.trn, 789.trn, 775.trn, 761.trn, 747.trn, | | 733.trn, 720.trn, 706.trn, 692.trn, 69.trn, 678.trn, 664.trn, | | 650.trn, 637.trn, 623.trn, 609.trn, 595.trn, 581.trn, 567.trn, | | 554.trn, 55.trn, 540.trn, 526.trn, 512.trn, 498.trn, 484.trn, | | 471.trn, 457.trn, 443.trn, 429.trn, 42.trn, 415.trn, 401.trn, | | 387.trn, 374.trn, 360.trn, 346.trn, 332.trn, 318.trn, 304.trn, | | 291.trn, 28.trn, 277.trn, 263.trn, 2560.trn, 2546.trn, 2533.trn, | | 2519.trn, 2505.trn, 2491.trn, 249.trn, 2477.trn, 2463.trn, | | 2450.trn, 2436.trn, 2422.trn, 2408.trn, 2394.trn, 2380.trn, | | 2367.trn, 2353.trn, 235.trn, 2339.trn, 2325.trn, 2311.trn, | | 2297.trn, 2283.trn, 2270.trn, 2256.trn, 2242.trn, 2228.trn, | | 2214.trn, 221.trn, 2200.trn, 2187.trn, 2173.trn, 2159.trn, | | 2145.trn, 2131.trn, 2117.trn, 2104.trn, 2090.trn, 208.trn, | | 2076.trn, 2062.trn, 2048.trn, 2034.trn, 2021.trn, 2007.trn, | | 1993.trn, 1979.trn, 1965.trn, 1951.trn, 194.trn, 1937.trn, | | 1924.trn, 1910.trn, 1896.trn, 1882.trn, 1868.trn, 1854.trn, | | 1841.trn, 1827.trn, 1813.trn, 180.trn, 1799.trn, 1785.trn, | | 1771.trn, 1758.trn, 1744.trn, 1730.trn, 1716.trn, 1702.trn, | | 1688.trn, 1675.trn, 1661.trn, 166.trn, 1647.trn, 1633.trn, | | 1619.trn, 1605.trn, 1591.trn, 1578.trn, 1564.trn, 1550.trn, | | 1536.trn, 1522.trn, 152.trn, 1508.trn, 1495.trn, 1481.trn, | | 1467.trn, 1453.trn, 1439.trn, 1425.trn, 1412.trn, 14.trn, | | 1398.trn, 1384.trn, 138.trn, 1370.trn, 1356.trn, 1342.trn, | | 1329.trn, 1315.trn, 1301.trn, 1287.trn, 1273.trn, 1259.trn, | | 125.trn, 1246.trn, 1232.trn, 1218.trn, 1204.trn, 1190.trn, | | 1176.trn, 1162.trn, 1149.trn, 1135.trn, 1121.trn, 111.trn, | | 1107.trn, 1093.trn, 1079.trn, 1066.trn, 1052.trn, 1038.trn, | | 1024.trn, 1010.trn, 0.trn | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | The following user files have been saved in the directory | | G:/Re200Fr1-5_2740_Working/dp0/CFX-5/CFX/Work1/Fluid Flow CFX_002: | | | | mon | +--------------------------------------------------------------------+ +--------------------------------------------------------------------+ | Warning! | | | | After waiting for 60 seconds, 1 solver manager process(es) appear | | not to have noticed that this run has ended. You may get errors | | removing some files if they are still open in the solver manager. | +--------------------------------------------------------------------+ This run of the ANSYS CFX Solver has finished. I am using following CCL This run of the CFX-13.0 Solver started at 18:51:18 on 30 Jan 2012 by user jc218370 on 332Z5Q1 (intel_xeon64.sse2_winnt) using the command: "C:\Program Files\ANSYS Inc\v130\CFX\bin\perllib\cfx5solve.pl" -batch -ccl runInput.ccl -fullname "Fluid Flow CFX_002" Setting up CFX Solver run ... +--------------------------------------------------------------------+ | | | CFX Command Language for Run | | | +--------------------------------------------------------------------+ LIBRARY: CEL: EXPRESSIONS: S = 0.31856 [K m^-1] To = 300 [K] Tst = To +S *Z Coordinate END END MATERIAL: Air at 25 C Material Description = Air at 25 C and 1 atm (dry) Material Group = Air Data, Constant Property Gases Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material EQUATION OF STATE: Density = 1.185 [kg m^-3] Molar Mass = 28.96 [kg kmol^-1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 1.0044E+03 [J kg^-1 K^-1] Specific Heat Type = Constant Pressure END REFERENCE STATE: Option = Specified Point Reference Pressure = 1 [atm] Reference Specific Enthalpy = 0. [J/kg] Reference Specific Entropy = 0. [J/kg/K] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 1.831E-05 [kg m^-1 s^-1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 2.61E-02 [W m^-1 K^-1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 0.01 [m^-1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^-1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^-1] END THERMAL EXPANSIVITY: Option = Value Thermal Expansivity = 0.003356 [K^-1] END END END END FLOW: Flow Analysis 1 SOLUTION UNITS: Angle Units = [rad] Length Units = [m] Mass Units = [kg] Solid Angle Units = [sr] Temperature Units = [K] Time Units = [s] END ANALYSIS TYPE: Option = Transient EXTERNAL SOLVER COUPLING: Option = None END INITIAL TIME: Option = Automatic with Value Time = 0 [s] END TIME DURATION: Option = Total Time Total Time = 28900 [s] END TIME STEPS: Option = Timesteps Timesteps = 7.226 [s] END END DOMAIN: Twin Fountain Stratified Coord Frame = Coord 0 Domain Type = Fluid Location = B20 BOUNDARY: Atm Boundary Type = OUTLET Location = F22.20 BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Normal Speed = 0 [m s^-1] Option = Normal Speed END END END BOUNDARY: Vent 1 Boundary Type = INLET Location = F19.20 BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END HEAT TRANSFER: Option = Static Temperature Static Temperature = 299.9575251 [K] END MASS AND MOMENTUM: Normal Speed = 0.00429 [m s^-1] Option = Normal Speed END END END BOUNDARY: Vent2 Boundary Type = INLET Location = F18.20 BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END HEAT TRANSFER: Option = Static Temperature Static Temperature = 299.9575251 [K] END MASS AND MOMENTUM: Normal Speed = 0.00429 [m s^-1] Option = Normal Speed END END END BOUNDARY: Wall Boundary Type = WALL Location = F21.20,F23.20,F24.20,F25.20,F26.20 BOUNDARY CONDITIONS: HEAT TRANSFER: Option = Adiabatic END MASS AND MOMENTUM: Option = No Slip Wall END END END DOMAIN MODELS: BUOYANCY MODEL: Buoyancy Reference Temperature = 300 [K] Gravity X Component = 0 [m s^-2] Gravity Y Component = 0 [m s^-2] Gravity Z Component = 9.81 [m s^-2] Option = Buoyant BUOYANCY REFERENCE LOCATION: Option = Automatic END 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: Option = Thermal Energy END THERMAL RADIATION MODEL: Option = None END TURBULENCE MODEL: Option = Laminar END END END INITIALISATION: Option = Automatic INITIAL CONDITIONS: Velocity Type = Cartesian CARTESIAN VELOCITY COMPONENTS: Option = Automatic with Value U = 0 [m s^-1] V = 0 [m s^-1] W = 0 [m s^-1] END STATIC PRESSURE: Option = Automatic with Value Relative Pressure = 1 [atm] END TEMPERATURE: Option = Automatic with Value Temperature = Tst END END END OUTPUT CONTROL: RESULTS: File Compression Level = Default Option = Standard END TRANSIENT RESULTS: Transient Results 1 File Compression Level = Default Include Mesh = No Option = Selected Variables Output Variables List = Temperature,Velocity OUTPUT FREQUENCY: Option = Time Interval Time Interval = 100 [s] END END END SOLVER CONTROL: ADVECTION SCHEME: Option = High Resolution END BODY FORCES: Body Force Averaging Type = Volume-Weighted END CONVERGENCE CONTROL: Maximum Number of Coefficient Loops = 5 Minimum Number of Coefficient Loops = 1 Timescale Control = Coefficient Loops END CONVERGENCE CRITERIA: Residual Target = 1.E-4 Residual Type = RMS END TRANSIENT SCHEME: Option = Second Order Backward Euler TIMESTEP INITIALISATION: Option = Automatic END END END END COMMAND FILE: Version = 13.0 Results Version = 13.0 END SIMULATION CONTROL: EXECUTION CONTROL: EXECUTABLE SELECTION: Double Precision = Off END INTERPOLATOR STEP CONTROL: Runtime Priority = Standard MEMORY CONTROL: Memory Allocation Factor = 1.0 END END PARALLEL HOST LIBRARY: HOST DEFINITION: host332z5q1 Remote Host Name = 332Z5Q1 Host Architecture String = winnt-amd64 Installation Root = C:\Program Files\ANSYS Inc\v%v\CFX END END PARTITIONER STEP CONTROL: Multidomain Option = Independent Partitioning Runtime Priority = Standard EXECUTABLE SELECTION: Use Large Problem Partitioner = Off END MEMORY CONTROL: Memory Allocation Factor = 1.0 END PARTITIONING TYPE: MeTiS Type = k-way Option = MeTiS Partition Size Rule = Automatic END END RUN DEFINITION: Run Mode = Full Solver Input File = Fluid Flow CFX.def END SOLVER STEP CONTROL: Runtime Priority = Standard MEMORY CONTROL: Memory Allocation Factor = 1.0 END PARALLEL ENVIRONMENT: Number of Processes = 1 Start Method = Serial END END END END Regards HMR |

Why do you say it could be numerical instability? You do not report a floating point error and have not included the residuals.
You have also forgotten the first thing to try when it does not converge - use a smaller time step. Also you have limited it to 5 coeff loops per time step. This should be more like 10 or 20. |

Hi Glenn,
Thanks for your reply. In this stratified simulation case I considered 0.0001 residual. I understand what you mean for figure out this problem but I am not familiar about the floating point error. |

What makes you think your simulation has a numerical instability?
Also, have you tried smaller time steps? |

Hi Gleen,
As I tried to carry on my simulation by changing modification in descretization and mesh but I am unable to find out the solution that's why I think may be problem in numerical instability. As departmnetal CFX license expires day before yesterday I am unable to do any simulation right now. I will modified this case according to your advice and let you know Cheers HMR |

Glen,
My simulation is working good now. thanks for your response and advice. Cheers HMR |

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