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November 13, 2013, 15:07 
Multiphase simulation of bubble rising

#1 
Member
niru
Join Date: Apr 2012
Posts: 55
Rep Power: 14 
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 

November 13, 2013, 16:43 

#2 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,830
Rep Power: 144 
This FAQ discusses this: http://www.cfdonline.com/Wiki/Ansys...do_about_it.3F


January 9, 2014, 07:13 
Same problem with me

#3 
New Member
Bitte56
Join Date: Mar 2013
Location: India
Posts: 15
Rep Power: 13 
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 

January 12, 2014, 05:53 

#4 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,830
Rep Power: 144 
The FAQ discusses a lot more than just changing time step size. What about all the other things to look at?


January 12, 2014, 23:59 
thank you

#5 
New Member
Bitte56
Join Date: Mar 2013
Location: India
Posts: 15
Rep Power: 13 
yes sir. i tried few other things and its converging now.


November 25, 2014, 13:57 

#6 
Member
azna
Join Date: Nov 2012
Posts: 30
Rep Power: 13 
are the equations for k epsilon model different if we use dispersed eulerian multiphase model or VOF model?


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bubble, multiphase, overflow, particle model 
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