[Niru]

I am trying to model the rise of a cryogenic vapor bubble in its liquid. The vapor bubble is more than the saturated temperature. I give the inlet for bubbles as inlet BC or by defining a source point.
I get an overflow exception after 2 coefficient loops are over and If I use inlet BC, program runs, it stops after some time 100 iterations.
I am not able to figure out the mistake, help required to run the program.
----------------------------------------------------
CCL file -partial file
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 = 2 [s]
END
TIME STEPS:
Option = Timesteps
Timesteps = 0.0002 [s]
END
END
DOMAIN: Default Domain
Coord Frame = Coord 0
Domain Type = Fluid
Location = B16
BOUNDARY: Default Domain Default
Boundary Type = WALL
Location = F22.16
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Option = Adiabatic
END
MASS AND MOMENTUM:
Option = No Slip Wall
END
WALL CONTACT MODEL:
Option = Use Volume Fraction
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
END
BOUNDARY: Presoutlet
Boundary Type = OPENING
Location = Top
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Normal to Boundary Condition
END
FLOW REGIME:
Option = Subsonic
END
HEAT TRANSFER:
Opening Temperature = 80 [K]
Option = Opening Temperature
END
MASS AND MOMENTUM:
Option = Opening Pressure and Direction
Relative Pressure = 0 [Pa]
END
TURBULENCE:
Option = Medium Intensity and Eddy Viscosity Ratio
END
END
FLUID: LN2
BOUNDARY CONDITIONS:
VOLUME FRACTION:
Option = Value
Volume Fraction = 1
END
END
END
FLUID: Nitrogen vapor
BOUNDARY CONDITIONS:
VOLUME FRACTION:
Option = Value
Volume Fraction = 0
END
END
END
END
BOUNDARY: Symmetry
Boundary Type = SYMMETRY
Location = sides
END
BOUNDARY: Symmetry2
Boundary Type = SYMMETRY
Location = FrontBack
END
BOUNDARY: Wall
Boundary Type = WALL
Location = Wall
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Fixed Temperature = 300 [K]
Option = Fixed Temperature
END
MASS AND MOMENTUM:
Option = Fluid Dependent
END
WALL CONTACT MODEL:
Option = Use Volume Fraction
END
WALL ROUGHNESS:
Option = Rough Wall
Sand Grain Roughness Height = 0.001 [m]
END
END
FLUID: LN2
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
END
END
END
FLUID: Nitrogen vapor
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
END
END
END
END
DOMAIN MODELS:
BUOYANCY MODEL:
Buoyancy Reference Density = 808 [kg m^-3]
Gravity X Component = 0 [m s^-2]
Gravity Y Component = -9.81 [m s^-2]
Gravity Z Component = 0 [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: LN2
Material = LN2
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID DEFINITION: Nitrogen vapor
Material = N2 at STP
Option = Material Library
MORPHOLOGY:
Mean Diameter = 8.7 [mm]
Option = Dispersed Fluid
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
FLUID: LN2
FLUID BUOYANCY MODEL:
Option = Density Difference
END
TURBULENCE MODEL:
Option = k epsilon
BUOYANCY TURBULENCE:
Option = None
END
END
TURBULENT WALL FUNCTIONS:
Option = Scalable
END
END
FLUID: Nitrogen vapor
FLUID BUOYANCY MODEL:
Option = Density Difference
END
TURBULENCE MODEL:
Option = Dispersed Phase Zero Equation
END
END
HEAT TRANSFER MODEL:
Homogeneous Model = Off
Option = Thermal Energy
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Homogeneous Model = False
Option = Fluid Dependent
END
END
FLUID PAIR: LN2 | Nitrogen vapor
Surface Tension Coefficient = 0.00885 [N m^-1]
INTERPHASE HEAT TRANSFER:
Option = Hughmark
END
INTERPHASE TRANSFER MODEL:
Option = Particle Model
END
MASS TRANSFER:
Option = None
END
MOMENTUM TRANSFER:
DRAG FORCE:
Option = Ishii Zuber
END
LIFT FORCE:
Option = None
END
TURBULENT DISPERSION FORCE:
Option = Favre Averaged Drag Force
Turbulent Dispersion Coefficient = 1.0
END
VIRTUAL MASS FORCE:
Option = None
END
WALL LUBRICATION FORCE:
Option = None
END
END
SURFACE TENSION MODEL:
Option = None
END
TURBULENCE TRANSFER:
ENHANCED TURBULENCE PRODUCTION MODEL:
Option = Sato Enhanced Eddy Viscosity
END
END
END
MULTIPHASE MODELS:
Homogeneous Model = Off
FREE SURFACE MODEL:
Option = Standard
END
END
SOURCE POINT: Source Point 1
Cartesian Coordinates = 0.015 [m], 0 [m], 0 [m]
Option = Cartesian Coordinates
FLUID: Nitrogen vapor
SOURCES:
EQUATION SOURCE: continuity
Option = Total Fluid Mass Source
Total Source = 0.008 [kg s^-1]
VARIABLE: T
Option = Value
Value = 77 [K]
END
VARIABLE: vel
Option = Cartesian Vector Components
xValue = 0 [m s^-1]
yValue = 0.16 [m s^-1]
zValue = 0 [m s^-1]
END
END
END
END
END
END
INITIALISATION:
Option = Automatic
FLUID: LN2
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
TEMPERATURE:
Option = Automatic with Value
Temperature = 77 [K]
END
TURBULENCE INITIAL CONDITIONS:
Option = Medium Intensity and Eddy Viscosity Ratio
END
VOLUME FRACTION:
Option = Automatic with Value
Volume Fraction = 1
END
END
END
FLUID: Nitrogen vapor
INITIAL CONDITIONS:
Velocity Type = Cartesian
CARTESIAN VELOCITY COMPONENTS:
Option = Automatic with Value
U = 0 [m s^-1]
V = 0.16 [m s^-1]
W = 0 [m s^-1]
END
TEMPERATURE:
Option = Automatic with Value
Temperature = 90 [K]
END
VOLUME FRACTION:
Option = Automatic with Value
Volume Fraction = 0
END
END
END
INITIAL CONDITIONS:
STATIC PRESSURE:
Option = Automatic with Value
Relative Pressure = 0 [Pa]
END
END
END
OUTPUT CONTROL:
RESULTS:
File Compression Level = Default
Option = Standard
END
TRANSIENT RESULTS: Transient Results 1
File Compression Level = Default
Option = Standard
OUTPUT FREQUENCY:
Option = Timestep Interval
Timestep Interval = 100
END
END
END
SOLVER CONTROL:
Turbulence Numerics = First Order
ADVECTION SCHEME:
Option = High Resolution
END
CONVERGENCE CONTROL:
Maximum Number of Coefficient Loops = 10
Minimum Number of Coefficient Loops = 1
Timescale Control = Coefficient Loops
END
CONVERGENCE CRITERIA:
Residual Target = 0.00001
Residual Type = MAX
END
MULTIPHASE CONTROL:
Volume Fraction Coupling = Coupled
END
TRANSIENT SCHEME:
Option = Second Order Backward Euler
TIMESTEP INITIALISATION:
Option = Automatic
END
END
END
END
COMMAND FILE:
END

[ghorrocks]

This FAQ discusses this: http://www.cfd-online.com/Wiki/Ansys...do_about_it.3F

[ARohit]

Hey brother,


I am also having the same prob. hav u found soln.?

please tell me . I tried by reducing auto time scale and making it 0.1 times and 0.01 times . respec. but only minor improvement i saw. solver stuck at around 100 iters.


Thanks in advance

[ghorrocks]

The FAQ discusses a lot more than just changing time step size. What about all the other things to look at?

[ARohit]

yes sir. i tried few other things and its converging now.

[azna]

are the equations for k- epsilon model different if we use dispersed eulerian multiphase model or VOF model?