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August 30, 2006, 11:42 
TwoPhase Buoyant Flow Issue

#1 
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Hi all
I am using CFX 10.0 in order to simulate air bubble behavior rising in a vertical pipe filled with stagnant water. I have chosen the follow sets: simulation type: transient, freesurface model, buoyant flow, gravity vector: (0;0;9.81), reference density: rho.air, Surface tension: 0.0718 N/m. I started from a spherical bubble which is located in pipe bottom. However, bubble does not rise. what is wrong? Thanks for your help 

August 31, 2006, 10:04 
Re: TwoPhase Buoyant Flow Issue

#2 
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Post your command file


August 31, 2006, 10:48 
Re: TwoPhase Buoyant Flow Issue

#3 
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Joe, thanks a lot for your reply. This is my ccl file, If you need any file please give me your email and I send to you.
# State file created: 2006/08/28 11:44:23 # CFX10.0 build 2005.10.2623.10 FLOW: COORD FRAME:Coord 1 Axis 3 Point = 0 [m], 0 [m], 1 [m] Coord Frame Type = Cartesian Option = Axis Points Origin Point = 0 [m], 0 [m], 0 [m] Plane 13 Point = 1 [m], 0 [m], 0 [m] Reference Coord Frame = Coord 0 END DOMAIN:conducto Coord Frame = Coord 1 Domain Type = Fluid Fluids List = Air Ideal Gas,Water Location = Assembly BOUNDARYared Boundary Type = WALL Coord Frame = Coord 1 Location = F16.17,F18.17,F19.17,F20.17,F21.17,F22.17 FLUID:Air Ideal Gas BOUNDARY CONDITIONS: WALL INFLUENCE ON FLOW: Option = Free Slip END END END FLUID:Water BOUNDARY CONDITIONS: WALL INFLUENCE ON FLOW: Option = No Slip WALL VELOCITY: Option = Cartesian Components Wall U = 0 [m s^1] Wall V = 0 [m s^1] Wall W = 0 [mm s^1] END END END END WALL CONTACT MODEL: Option = Use Volume Fraction END END DOMAIN MODELS: BUOYANCY MODEL: Buoyancy Reference Density = 1.164 [kg m^3] 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: Cartesian Coordinates = 0 [m], 0 [m], 0.03 [m] Option = Cartesian Coordinates END END DOMAIN MOTION: Option = Stationary END MESH DEFORMATION: Option = None END REFERENCE PRESSURE: Reference Pressure = 1 [atm] END END FLUID:Air Ideal Gas FLUID MODELS: FLUID BUOYANCY MODEL: Option = Density Difference END MORPHOLOGY: Minimum Volume Fraction = 10e12 Option = Continuous Fluid END END END FLUID:Water FLUID MODELS: FLUID BUOYANCY MODEL: Option = Density Difference END MORPHOLOGY: Minimum Volume Fraction = 10e12 Option = Continuous Fluid END END END FLUID MODELS: COMBUSTION MODEL: Option = None END HEAT TRANSFER MODEL: Fluid Temperature = 30 [C] Homogeneous Model = False Option = Isothermal END THERMAL RADIATION MODEL: Option = None END TURBULENCE MODEL: Homogeneous Model = False Option = Laminar END END FLUID PAIR:Air Ideal Gas  Water Surface Tension Coefficient = 0.0718 [N m^1] INTERPHASE TRANSFER MODEL: Maximum Length Scale for Area Density = 0.1 [mm] Option = Free Surface END MASS TRANSFER: Option = None END MOMENTUM TRANSFER: DRAG FORCE: Drag Coefficient = 0.44 Option = Drag Coefficient END END SURFACE TENSION MODEL: Curvature Under Relaxation Factor = 0.25 Option = None Volume Fraction Smoothing Type = VolumeWeighted END END INITIALISATION: Coord Frame = Coord 1 Option = Automatic FLUID:Air Ideal Gas INITIAL CONDITIONS: Velocity Type = Cartesian CARTESIAN VELOCITY COMPONENTS: Option = Automatic with Value U = 0 [m s^1] V = 0 [m s^1] W = 0 [mm s^1] END VOLUME FRACTION: Option = Automatic with Value Volume Fraction = FVG END END END FLUID:Water 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 VOLUME FRACTION: Option = Automatic with Value Volume Fraction = FVL END END END INITIAL CONDITIONS: STATIC PRESSURE: Option = Automatic with Value Relative Pressure = PI END END END MULTIPHASE MODELS: Homogeneous Model = False FREE SURFACE MODEL: Interface Compression Level = 1 Option = Standard 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 = Absolute Pressure,Air Ideal Gas.Smoothed Volume Fraction,Air Ideal Gas.Velocity u,Air Ideal Gas.Velocity v,Air Ideal Gas.Velocity w,Air Ideal Gas.Volume Fraction,Total Pressure,Water.Smoothed Volume Fraction,Water.Velocity,Water.Volume Fraction Time Interval = 0.1 [s] END END SIMULATION TYPE: Option = Transient INITIAL TIME: Option = Automatic with Value Time = 0 [s] END TIME DURATION: Option = Total Time Total Time = 5 [s] END TIME STEPS: Option = Timesteps Timesteps = 0.1 [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 = 10 Timescale Control = Coefficient Loops END CONVERGENCE CRITERIA: Residual Target = 1.E4 Residual Type = RMS END TRANSIENT SCHEME: Option = Second Order Backward Euler END END END LIBRARY: CEL: EXPRESSIONS: FVG = 1FVL FVL = step(esferoide) PI = g*997[kg m^3]*(0.03[m]z) esferoide = x^2/(0.4*1[mm^1])^2+y^2/(0.4*1[mm^1])^2+(z4[mm^1])^2/(3*1[mm^1])^21 END END MATERIAL:Air Ideal Gas Material Description = Air Ideal Gas (constant Cp) Material Group = Air Data, Calorically Perfect Ideal Gases Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material ABSORPTION COEFFICIENT: Absorption Coefficient = 0.01 [m^1] Option = Value END DYNAMIC VISCOSITY: Dynamic Viscosity = 1.831E05 [kg m^1 s^1] Option = Value END EQUATION OF STATE: Molar Mass = 28.96 [kg kmol^1] Option = Ideal Gas 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 = 2.61E2 [W m^1 K^1] END 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 = 1.831E05 [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 = 2.61E02 [W m^1 K^1] END END END MATERIAL:Water Ideal Gas Material Description = Water Vapour Ideal Gas (100 C and 1 atm) Material Group = Calorically Perfect Ideal Gases, Water Data Option = Pure Substance Thermodynamic State = Gas PROPERTIES: Option = General Material ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^1] Option = Value END DYNAMIC VISCOSITY: Dynamic Viscosity = 9.4E06 [kg m^1 s^1] Option = Value END EQUATION OF STATE: Molar Mass = 18.02 [kg kmol^1] Option = Ideal Gas 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 = 1.014 [bar] Reference Specific Enthalpy = 0.0 [J/kg] Reference Specific Entropy = 0.0 [J/kg/K] Reference Temperature = 100 [C] Specific Heat Capacity = 2080.1 [J kg^1 K^1] Specific Heat Type = Constant Pressure END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 193E04 [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 = 2.57E04 [K^1] ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [m^1] Option = Value END DYNAMIC VISCOSITY: Dynamic Viscosity = 8.899E4 [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 MATERIAL:Aluminium Material Group = CHT Solids, Particle Solids Option = Pure Substance Thermodynamic State = Solid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 2702 [kg m^3] Molar Mass = 26.98 [kg kmol^1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Reference Specific Enthalpy = 0 [J/kg] Reference Specific Entropy = 0 [J/kg/K] Reference Temperature = 25 [C] Specific Heat Capacity = 9.03E+02 [J kg^1 K^1] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 237 [W m^1 K^1] END END END MATERIAL:Steel Material Group = CHT Solids, Particle Solids Option = Pure Substance Thermodynamic State = Solid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 7854 [kg m^3] Molar Mass = 55.85 [kg kmol^1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Reference Specific Enthalpy = 0 [J/kg] Reference Specific Entropy = 0 [J/kg/K] Reference Temperature = 25 [C] Specific Heat Capacity = 4.34E+02 [J kg^1 K^1] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 60.5 [W m^1 K^1] END END END MATERIAL:Copper Material Group = CHT Solids, Particle Solids Option = Pure Substance Thermodynamic State = Solid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 8933 [kg m^3] Molar Mass = 63.55 [kg kmol^1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Reference Specific Enthalpy = 0 [J/kg] Reference Specific Entropy = 0 [J/kg/K] Reference Temperature = 25 [C] Specific Heat Capacity = 3.85E+02 [J kg^1 K^1] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 401.0 [W m^1 K^1] END END END MATERIAL GROUP:Air Data Group Description = Ideal gas and constant property air. Constant properties are for dry air at STP (0 C, 1 atm) and 25 C, 1 atm. END MATERIAL GROUP:Water Data Group Description = Liquid and vapour water materials with constant properties. Can be combined with NASA SP273 materials for combustion modelling. END MATERIAL GROUP:Gas Phase Combustion Group Description = Materials which can be use for gas phase combustion. Properties are specified using the NASA SP273 format. END MATERIAL GROUP:Constant Property Gases Group Description = Gaseous substances with constant properties. Properties are calculated at STP (0C and 1 atm). Can be combined with NASA SP273 materials for combustion modelling. END MATERIAL GROUP:Calorically Perfect Ideal Gases Group Description = Ideal gases with constant specific heat capacity. Specific heat is evaluated at STP. END MATERIAL GROUP:Constant Property Liquids Group Description = Liquid substances with constant properties. END MATERIAL GROUP:CHT Solids Group Description = Pure solid substances that can be used for conjugate heat transfer. END MATERIAL GROUP:Particle Solids Group Description = Pure solid substances that can be used for particle tracking END MATERIAL GROUP:Soot Group Description = Solid substances that can be used when performing soot modelling END MATERIAL GROUP:User Group Description = Materials that are defined by the user END MATERIAL GROUP:Interphase Mass Transfer Group Description = Materials with reference properties suitable for performing either Eulerian or Lagrangian multiphase mass transfer problems.Examples include cavitation, evaporation or condensation. END MATERIAL GROUPry Redlich Kwong Group Description = Materials with properties specified using the built in Redlich Kwong Equation of State. Suitable for dry real gas modelling. END MATERIAL GROUP:Wet Redlich Kwong Group Description = Materials with properties specified using the built in Redlich Kwong Equation of State. Suitable for wet real gas modelling. END MATERIAL GROUPry Redlich Kwong RGP Group Description = Materials with properties specified in TASCflow RGP files using the Redlich Kwong Equation of State. Suitable for dry real gas modelling. END MATERIAL GROUP:Wet Redlich Kwong RGP Group Description = Materials with properties specified in TASCflow RGP files using the Redlich Kwong Equation of State. Suitable for wet real gas modelling. END MATERIAL GROUPry Steam Group Description = Materials with properties specified in TASCflow RGP files using the Vukalovich virial equation of state. Suitable for dry steam modelling. END MATERIAL GROUP:Wet Steam Group Description = Materials with properties specified in TASCflow RGP files using the Vukalovich virial equation of state. Suitable for wet steam modelling. END MATERIAL GROUP:Redlich Kwong Dry Steam Group Description = Water materials which use the Redlich Kwong equation of state. Suitable for dry steam modelling. END MATERIAL GROUP:Redlich Kwong Wet Steam Group Description = Water materials which use the Redlich Kwong equation of state. Suitable for condensing steam modelling. END MATERIAL GROUP:Redlich Kwong Dry Refrigerants Group Description = Common refrigerants which use the Redlich Kwong equation of state. Suitable for dry real gas models. END MATERIAL GROUP:Redlich Kwong Wet Refrigerants Group Description = Common refrigerants which use the Redlich Kwong equation of state. Suitable for condensing real gas models. END MATERIAL GROUP:Redlich Kwong Dry Hydrocarbons Group Description = Common hydrocarbons which use the Redlich Kwong equation of state. Suitable for dry real gas models. END MATERIAL GROUP:Redlich Kwong Wet Hydrocarbons Group Description = Common hydrocarbons which use the Redlich Kwong equation of state. Suitable for condensing real gas models. END END COMMAND FILE: Version = 10.0 END 

August 31, 2006, 11:40 
Re: TwoPhase Buoyant Flow Issue

#4 
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Why is BUOYANCY REFERENCE LOCATION: located at that particular position?
The air isnt feeling the gravity body force ... 

August 31, 2006, 12:02 
Re: TwoPhase Buoyant Flow Issue

#5 
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Since ptotal=p+pref+rho.ref*(zzref)*g, I choose zref on top of chanel in order to add hidrostatyc contribution due water. This is true if rho.ref=rho.water, but it isnt, right? rho.ref=rho.air.It`s my mistake. Where can I set zref?


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