i want to set two bubble in initial condition, someone gave me a suggestion, the combination of step function is used, however,the cfx is terminal because of error,just like this:

i do not know how to do? +--------------------------------------------------------------------+ | | | CFX Command Language for Run | | | +--------------------------------------------------------------------+

LIBRARY:

CEL:

EXPRESSIONS:

DenH = 1000 [kg m^-3]

DownH1 = 0.040 [m]

Pres1 = DenH*g*DownH1

Rbubble1 = 0.001 [m]

UpVFbubble1 = step(((0.0008 [m]^2-(x-0.0015 [m])^2-(z-0.0015 \

[m])^2))/1[m^2])+step(((0.0008 [m]^2-(x-0.0015 [m])^2-(z-0.0025 \

[m])^2))/1[m^2])

UpVFwater1 = 1-UpVFbubble1

dist1 = Rbubble1-sqrt((x-0.0025[m])^2+(z-0.002[m])^2)

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

Thermal Expansivity = 0.003356 [K^-1]

ABSORPTION COEFFICIENT:

Absorption Coefficient = 0.01 [m^-1]

Option = Value

END

DYNAMIC VISCOSITY:

Dynamic Viscosity = 1.831E-05 [kg m^-1 s^-1]

Option = Value

END

EQUATION OF STATE:

Density = 1.185 [kg m^-3]

Molar Mass = 28.96 [kg kmol^-1]

Option = Value

END

REFRACTIVE INDEX:

Option = Value

Refractive Index = 1.0 [m m^-1]

END

SCATTERING COEFFICIENT:

Option = Value

Scattering Coefficient = 0.0 [m^-1]

END

SPECIFIC HEAT CAPACITY:

Option = Value

Reference Pressure = 1 [atm]

Reference Specific Enthalpy = 0. [J/kg]

Reference Specific Entropy = 0. [J/kg/K]

Reference Temperature = 25 [C]

Specific Heat Capacity = 1.0044E+03 [J kg^-1 K^-1]

Specific Heat Type = Constant Pressure

END

THERMAL CONDUCTIVITY:

Option = Value

Thermal Conductivity = 2.61E-02 [W m^-1 K^-1]

END

END

END

MATERIAL: Water

Material Description = Water (liquid)

Material Group = Water Data, Constant Property Liquids

Option = Pure Substance

Thermodynamic State = Liquid

PROPERTIES:

Option = General Material

Thermal Expansivity = 2.57E-04 [K^-1]

ABSORPTION COEFFICIENT:

Absorption Coefficient = 1.0 [m^-1]

Option = Value

END

DYNAMIC VISCOSITY:

Dynamic Viscosity = 8.899E-4 [kg m^-1 s^-1]

Option = Value

END

EQUATION OF STATE:

Density = 997.0 [kg m^-3]

Molar Mass = 18.02 [kg kmol^-1]

Option = Value

END

REFRACTIVE INDEX:

Option = Value

Refractive Index = 1.0 [m m^-1]

END

SCATTERING COEFFICIENT:

Option = Value

Scattering Coefficient = 0.0 [m^-1]

END

SPECIFIC HEAT CAPACITY:

Option = Value

Reference Pressure = 1 [atm]

Reference Specific Enthalpy = 0.0 [J/kg]

Reference Specific Entropy = 0.0 [J/kg/K]

Reference Temperature = 25 [C]

Specific Heat Capacity = 4181.7 [J kg^-1 K^-1]

Specific Heat Type = Constant Pressure

END

THERMAL CONDUCTIVITY:

Option = Value

Thermal Conductivity = 0.6069 [W m^-1 K^-1]

END

END

END END EXECUTION CONTROL:

PARALLEL HOST LIBRARY:

HOST DEFINITION: b

Installation Root = C:\CFXb\CFX-%v

Host Architecture String = intel_pentium_winnt5.1

END

END

PARTITIONER STEP CONTROL:

Multidomain Option = Coupled Partitioning

Runtime Priority = Standard

MEMORY CONTROL:

Memory Allocation Factor = 1.0

END

PARTITIONING TYPE:

MeTiS Type = k-way

Option = MeTiS

Partition Size Rule = Automatic

END

END

RUN DEFINITION:

Definition File = D:/xjj/2bubble1.def

Interpolate Initial Values = Off

Run Mode = Full

END

SOLVER STEP CONTROL:

Runtime Priority = Standard

EXECUTABLE SELECTION:

Double Precision = Off

END

MEMORY CONTROL:

Memory Allocation Factor = 1.0

END

PARALLEL ENVIRONMENT:

Number of Processes = 1

Start Method = Serial

END

END END FLOW:

DOMAIN: Domain 1

Coord Frame = Coord 0

Domain Type = Fluid

Fluids List = Air at 25 C,Water

Location = Assembly

BOUNDARY: out

Boundary Type = OPENING

Location = OUTLET

BOUNDARY CONDITIONS:

FLOW DIRECTION:

Option = Normal to Boundary Condition

END

FLOW REGIME:

Option = Subsonic

END

MASS AND MOMENTUM:

Option = Opening Pressure and Direction

Relative Pressure = 0 [Pa]

END

END

FLUID: Air at 25 C

BOUNDARY CONDITIONS:

VOLUME FRACTION:

Option = Value

Volume Fraction = 0

END

END

END

FLUID: Water

BOUNDARY CONDITIONS:

VOLUME FRACTION:

Option = Value

Volume Fraction = 1

END

END

END

END

BOUNDARY: sym1

Boundary Type = SYMMETRY

Location = FRONT

END

BOUNDARY: sym2

Boundary Type = SYMMETRY

Location = BACK

END

BOUNDARY: Domain 1 Default

Boundary Type = WALL

Location = INLET,SURFS A,SURFS B

BOUNDARY CONDITIONS:

WALL INFLUENCE ON FLOW:

Option = No Slip

END

END

FLUID PAIR: Air at 25 C | Water

BOUNDARY CONDITIONS:

WALL ADHESION:

Option = None

END

END

END

END

DOMAIN MODELS:

BUOYANCY MODEL:

Buoyancy Reference Density = 1.185 [kg m^-3]

Gravity X Component = 0 [m s^-2]

Gravity Y Component = 0 [m s^-2]

Gravity Z Component = -9.8 [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: Air at 25 C

FLUID MODELS:

FLUID BUOYANCY MODEL:

Option = Density Difference

END

MORPHOLOGY:

Option = Continuous Fluid

END

END

END

FLUID: Water

FLUID MODELS:

FLUID BUOYANCY MODEL:

Option = Density Difference

END

MORPHOLOGY:

Option = Continuous Fluid

END

END

END

FLUID MODELS:

COMBUSTION MODEL:

Option = None

END

HEAT TRANSFER MODEL:

Fluid Temperature = 25 [C]

Homogeneous Model = True

Option = Isothermal

END

THERMAL RADIATION MODEL:

Option = None

END

TURBULENCE MODEL:

Option = Laminar

END

END

FLUID PAIR: Air at 25 C | Water

Surface Tension Coefficient = 0.07256 [N m^-1]

INTERPHASE TRANSFER MODEL:

Option = Free Surface

END

MASS TRANSFER:

Option = None

END

SURFACE TENSION MODEL:

Curvature Under Relaxation Factor = 0.25

Option = Continuum Surface Force

Primary Fluid = Water

Volume Fraction Smoothing Type = Volume-Weighted

END

END

MULTIPHASE MODELS:

Homogeneous Model = On

FREE SURFACE MODEL:

Option = Standard

END

END

END

INITIALISATION:

Option = Automatic

FLUID: Air at 25 C

INITIAL CONDITIONS:

VOLUME FRACTION:

Option = Automatic with Value

Volume Fraction = UpVFbubble1

END

END

END

FLUID: Water

INITIAL CONDITIONS:

VOLUME FRACTION:

Option = Automatic with Value

Volume Fraction = UpVFwater1

END

END

END

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 = Pres1

END

END

END

OUTPUT CONTROL:

RESULTS:

File Compression Level = Default

Option = Standard

END

TRANSIENT RESULTS: Transient Results 1

File Compression Level = Default

Option = Standard

Time Interval = 0.002 [s]

END

END

SIMULATION TYPE:

Option = Transient

INITIAL TIME:

Option = Automatic with Value

Time = 0 [s]

END

TIME DURATION:

Option = Total Time

Total Time = 1 [s]

END

TIME STEPS:

Option = Timesteps

Timesteps = 0.0001 [s]

END

END

SOLUTION UNITS:

Angle Units = [rad]

Length Units = [m]

Mass Units = [kg]

Solid Angle Units = [sr]

Temperature Units = [K]

Time Units = [s]

END

SOLVER CONTROL:

ADVECTION SCHEME:

Option = High Resolution

END

CONVERGENCE CONTROL:

Maximum Number of Coefficient Loops = 15

Timescale Control = Coefficient Loops

END

CONVERGENCE CRITERIA:

Residual Target = 0.00001

Residual Type = RMS

END

TRANSIENT SCHEME:

Option = Second Order Backward Euler

END

END END COMMAND FILE:

Version = 10.0

Results Version = 10.0 END

+--------------------------------------------------------------------+ | | | Solver | | | +--------------------------------------------------------------------+

+--------------------------------------------------------------------+ | | | ANSYS CFX Solver 10.0 | | | | Version 2005.07.11-10.24 Mon Jul 11 10:26:04 GMTDT 2005 | | | | Executable Attributes | | | | single-32bit-optimised-supfort-noprof-nospag-lcomp | | | | Copyright 1996-2005 ANSYS Europe Ltd. | +--------------------------------------------------------------------+

+--------------------------------------------------------------------+ | Job Information | +--------------------------------------------------------------------+

Run mode: serial run

Host computer: B Job started: Mon Jan 14 14:29:22 2008

+--------------------------------------------------------------------+ | Memory Allocated for Run (Actual usage may be less) | +--------------------------------------------------------------------+

Data Type Kwords Words/Node Words/Elem Kbytes Bytes/Node

Real 34615.5 432.69 884.15 135216.9 1730.78 Integer 6051.7 75.65 154.57 23639.5 302.59 Character 2442.3 30.53 62.38 2385.0 30.53 Logical 40.0 0.50 1.02 156.2 2.00 Double 477.8 5.97 12.20 3732.9 47.78

+--------------------------------------------------------------------+ | Total Number of Nodes, Elements, and Faces | +--------------------------------------------------------------------+

Domain Name : Domain 1

Total Number of Nodes = 80000

Total Number of Elements = 39151

Total Number of Hexahedrons = 39151

Total Number of Faces = 79998

+--------------------------------------------------------------------+ | Buoyancy Reference Information | +--------------------------------------------------------------------+

Domain Group: Domain 1

Buoyancy has been activated. The absolute pressure will include

hydrostatic pressure contribution, using the following reference

coordinates: ( 1.50000E-03, 5.00000E-05, 4.50000E-02). ---------------------------------- Error in subroutine GET_SPECVAR : Specified values for Water.Conservative Volume Fraction are out of bounds on Domain 1 GETVAR originally called by subroutine CAL_GVar

+--------------------------------------------------------------------+ | Writing crash recovery file | +--------------------------------------------------------------------+

+--------------------------------------------------------------------+ | An error has occurred in cfx5solve: | | | | The CFX-5 solver could not be started, or exited with return code | | 255: . No results file has been created. | +--------------------------------------------------------------------+

End of solution stage.

+--------------------------------------------------------------------+ | Warning! | | | | The CFX-5 Solver has written a crash recovery file. This file has | | been saved as D:\xjj\jingzhi\2bubble1_006.res.err and may be an | | aid to diagnosing the problem or restarting the run. More details | | should be available in the solver output section of the output | | file. Note that a lock file was left for the crash file when the | | solver exited, and so it is probably incomplete. | +--------------------------------------------------------------------+

+--------------------------------------------------------------------+ | The following user files have been saved in the directory | | D:\xjj\jingzhi\2bubble1_006: | | | | mon | +--------------------------------------------------------------------+

This run of the CFX-5 Solver has finished.

Hi,

The error message is saying your function is returning values which are out of bounds, that is smaller than 0 or greater than 1. Check the function to calculate the volume fraction.

Glenn Horrocks