
[Sponsors] 
July 8, 2010, 12:03 
Constant velocity of the material

#1 
New Member
Join Date: May 2010
Posts: 21
Rep Power: 7 
Prompt what assign the border conditions for pipe of the constant section that velocity of the material moving inwardly pipes was constant (0.02 м/с) on the whole length.


July 8, 2010, 12:46 

#2 
Senior Member
Joshua Counsil
Join Date: Jul 2009
Location: Halifax, Nova Scotia, Canada
Posts: 366
Rep Power: 9 
...Come again?


July 9, 2010, 06:04 

#3 
New Member
Join Date: May 2010
Posts: 21
Rep Power: 7 
Again, probably bad interpreter conveyed meaning:
What boundary conditions are put on the input and output for the speed in the pipe was at a constant level (0,02 m / s) As the flow  water. 

July 9, 2010, 07:49 

#4 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 11,567
Rep Power: 90 
Sorry, I still don't understand what you are asking.
Are you asking what boundary conditions to put on a pipe flowing at 0.02m/s? If so then read the documentation, it describes the choice of boundary conditions. Usually you want a velocity inlet and a pressure outlet. 

July 9, 2010, 08:00 

#5 
New Member
Join Date: May 2010
Posts: 21
Rep Power: 7 
with these conditions do not get a flat rate with the peaks (drawing), it is necessary that the rate remained constant over the length.
http://imagepost.ru/?v=173/Chart.png 

July 9, 2010, 11:58 

#6 
Senior Member
Joshua Counsil
Join Date: Jul 2009
Location: Halifax, Nova Scotia, Canada
Posts: 366
Rep Power: 9 
Is "z" the centerline velocity? Could you give us some more information about the simulation? Maybe you could post a picture of the domain, mesh, etc.


July 10, 2010, 10:51 

#7  
New Member
Join Date: May 2010
Posts: 21
Rep Power: 7 
Quote:
http://depositfiles.com/files/risv79gx1 

July 10, 2010, 13:59 

#8 
Senior Member
Joshua Counsil
Join Date: Jul 2009
Location: Halifax, Nova Scotia, Canada
Posts: 366
Rep Power: 9 
Unfortunately, I'm away from the office until July 19 and don't have access to CFX. Sorry, Sas.


July 10, 2010, 22:29 

#9 
New Member
Join Date: May 2010
Posts: 21
Rep Power: 7 

July 11, 2010, 07:37 

#10 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 11,567
Rep Power: 90 
And I don't look at res files from the forum. Can you post the CCL of your simulation?
Your graph has the value varying between 0.02001 and 0.01998. If you are asking why isn't it 0.02 then a) you have not converged far enough, b) use double precision numerics and c) it will always have some variation due to a numerical solution being used. 

July 12, 2010, 07:44 

#11  
New Member
Join Date: May 2010
Posts: 21
Rep Power: 7 
Quote:
http://depositfiles.com/files/risv79gx1 or CCL http://depositfiles.com/files/s7xf62km1 

July 12, 2010, 07:59 

#12 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 11,567
Rep Power: 90 
It does not let me download it. Can you post the CCL on the forum?


July 12, 2010, 10:14 

#13  
New Member
Join Date: May 2010
Posts: 21
Rep Power: 7 
Quote:
# State file created: 2010/07/12 19:41:56 # CFX12.0.1 build 2009.04.1423.02 LIBRARY: 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: CHT Solids Group Description = Pure solid substances that can be used for conjugate \ heat transfer. 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 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: Constant Property Liquids Group Description = Liquid substances with constant properties. END MATERIAL GROUP: Dry Peng Robinson Group Description = Materials with properties specified using the built \ in Peng Robinson equation of state. Suitable for dry real gas modelling. END MATERIAL GROUP: Dry 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: Dry Steam Group Description = Materials with properties specified using the IAPWS \ equation of state. Suitable for dry steam modelling. END MATERIAL GROUP: Gas Phase Combustion Group Description = Ideal gas materials which can be use for gas phase \ combustion. Ideal gas specific heat coefficients are specified using \ the NASA SP273 format. END MATERIAL GROUP: IAPWS IF97 Group Description = Liquid, vapour and binary mixture materials which use \ the IAPWS IF97 equation of state. Materials are suitable for \ compressible liquids, phase change calculations and dry steam flows. 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 GROUP: Liquid Phase Combustion Group Description = Liquid and homogenous binary mixture materials which \ can be included with Gas Phase Combustion materials if combustion \ modelling also requires phase change (eg: evaporation) for certain \ components. END MATERIAL GROUP: Particle Solids Group Description = Pure solid substances that can be used for particle \ tracking END MATERIAL GROUP: Peng Robinson Dry Hydrocarbons Group Description = Common hydrocarbons which use the Peng Robinson \ equation of state. Suitable for dry real gas models. END MATERIAL GROUP: Peng Robinson Dry Refrigerants Group Description = Common refrigerants which use the Peng Robinson \ equation of state. Suitable for dry real gas models. END MATERIAL GROUP: Peng Robinson Dry Steam Group Description = Water materials which use the Peng Robinson equation \ of state. Suitable for dry steam modelling. END MATERIAL GROUP: Peng Robinson Wet Hydrocarbons Group Description = Common hydrocarbons which use the Peng Robinson \ equation of state. Suitable for condensing real gas models. END MATERIAL GROUP: Peng Robinson Wet Refrigerants Group Description = Common refrigerants which use the Peng Robinson \ equation of state. Suitable for condensing real gas models. END MATERIAL GROUP: Peng Robinson Wet Steam Group Description = Water materials which use the Peng Robinson equation \ of state. Suitable for condensing steam modelling. END MATERIAL GROUP: Real Gas Combustion Group Description = Real gas materials which can be use for gas phase \ combustion. Ideal gas specific heat coefficients are specified using \ the NASA SP273 format. 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 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 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 Hydrocarbons Group Description = Common hydrocarbons which use the Redlich Kwong \ equation of state. Suitable for condensing 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 Wet Steam Group Description = Water materials which use the Redlich Kwong equation \ of state. Suitable for condensing steam modelling. 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: 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: Wet Peng Robinson Group Description = Materials with properties specified using the built \ in Peng Robinson equation of state. Suitable for wet 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 GROUP: Wet Steam Group Description = Materials with properties specified using the IAPWS \ equation of state. Suitable for wet steam modelling. 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 EQUATION OF STATE: Molar Mass = 28.96 [kg kmol^1] Option = Ideal Gas 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 = 1.831E05 [kg m^1 s^1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 2.61E2 [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 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 = 1.831E05 [kg m^1 s^1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 2.61E02 [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 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 Specific Heat Capacity = 9.03E+02 [J kg^1 K^1] END REFERENCE STATE: Option = Specified Point Reference Specific Enthalpy = 0 [J/kg] Reference Specific Entropy = 0 [J/kg/K] Reference Temperature = 25 [C] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 237 [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 Specific Heat Capacity = 3.85E+02 [J kg^1 K^1] END REFERENCE STATE: Option = Specified Point Reference Specific Enthalpy = 0 [J/kg] Reference Specific Entropy = 0 [J/kg/K] Reference Temperature = 25 [C] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 401.0 [W m^1 K^1] END END END MATERIAL: Soot Material Group = Soot Option = Pure Substance Thermodynamic State = Solid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 2000 [kg m^3] Molar Mass = 12 [kg kmol^1] Option = Value END REFERENCE STATE: Option = Automatic END ABSORPTION COEFFICIENT: Absorption Coefficient = 0 [m^1] Option = Value END END END MATERIAL: Spek Material Group = User Option = Pure Substance Thermodynamic State = Liquid PROPERTIES: Option = General Material EQUATION OF STATE: Density = 2600 [kg m^3] Molar Mass = 1.0 [kg kmol^1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 1110 [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^1] Reference Specific Entropy = 0 [J kg^1 K^1] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 0.01 [kg m^1 s^1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 0.34 [W m^1 K^1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 10 [m^1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 25 [m^1] END REFRACTIVE INDEX: Option = Value Refractive Index = 4 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 Specific Heat Capacity = 4.34E+02 [J kg^1 K^1] END REFERENCE STATE: Option = Specified Point Reference Specific Enthalpy = 0 [J/kg] Reference Specific Entropy = 0 [J/kg/K] Reference Temperature = 25 [C] END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 60.5 [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 EQUATION OF STATE: Density = 997.0 [kg m^3] Molar Mass = 18.02 [kg kmol^1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 4181.7 [J kg^1 K^1] Specific Heat Type = Constant Pressure END REFERENCE STATE: Option = Specified Point Reference Pressure = 1 [atm] Reference Specific Enthalpy = 0.0 [J/kg] Reference Specific Entropy = 0.0 [J/kg/K] Reference Temperature = 25 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 8.899E4 [kg m^1 s^1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 0.6069 [W m^1 K^1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [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 = 2.57E04 [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 EQUATION OF STATE: Molar Mass = 18.02 [kg kmol^1] Option = Ideal Gas END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 2080.1 [J kg^1 K^1] Specific Heat Type = Constant Pressure END REFERENCE STATE: Option = Specified Point Reference Pressure = 1.014 [bar] Reference Specific Enthalpy = 0. [J/kg] Reference Specific Entropy = 0. [J/kg/K] Reference Temperature = 100 [C] END DYNAMIC VISCOSITY: Dynamic Viscosity = 9.4E06 [kg m^1 s^1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 193E04 [W m^1 K^1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 1.0 [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 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 = Steady State EXTERNAL SOLVER COUPLING: Option = None END END DOMAIN: Default Domain Coord Frame = Coord 0 Domain Type = Fluid Location = B11 BOUNDARY: Boundary 1 Boundary Type = SYMMETRY Location = sym2 END BOUNDARY: Default Domain Default Boundary Type = WALL Location = F14.11,F40.11 BOUNDARY CONDITIONS: MASS AND MOMENTUM: Option = Free Slip Wall END END END BOUNDARY: in Boundary Type = INLET Location = in BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Normal Speed = 0.02 [m s^1] Option = Normal Speed END END END BOUNDARY: out Boundary Type = OUTLET Location = out BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Option = Average Static Pressure Pressure Profile Blend = 0.05 Relative Pressure = 0 [Pa] END PRESSURE AVERAGING: Option = Average Over Whole Outlet END END END DOMAIN MODELS: BUOYANCY MODEL: Option = Non Buoyant END DOMAIN MOTION: Option = Stationary END MESH DEFORMATION: Option = None END REFERENCE PRESSURE: Reference Pressure = 1 [atm] END END FLUID DEFINITION: Fluid 1 Material = Spek Option = Material Library MORPHOLOGY: Option = Continuous Fluid END END FLUID MODELS: COMBUSTION MODEL: Option = None END HEAT TRANSFER MODEL: Fluid Temperature = 25 [C] Option = Isothermal END THERMAL RADIATION MODEL: Option = None END TURBULENCE MODEL: Option = Laminar END END END OUTPUT CONTROL: RESULTS: File Compression Level = Default Option = Standard END END SOLVER CONTROL: ADVECTION SCHEME: Option = High Resolution END CONVERGENCE CONTROL: Length Scale Option = Conservative Maximum Number of Iterations = 1000 Minimum Number of Iterations = 1 Timescale Control = Auto Timescale Timescale Factor = 1.0 END CONVERGENCE CRITERIA: Residual Target = 1.E4 Residual Type = RMS END DYNAMIC MODEL CONTROL: Global Dynamic Model Control = On END END END COMMAND FILE: Version = 12.0.1 END 

July 12, 2010, 19:12 

#14 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 11,567
Rep Power: 90 
So it looks like you are doing a simple flow analysis with free slip walls and are wondering why the velocity is not 0.02m/s everywhere. Why did you not say this?
The answer is simple. Your convergence is very loose. Converge tighter. 

July 13, 2010, 08:00 

#15 
New Member
Join Date: May 2010
Posts: 21
Rep Power: 7 
that is, as I understand you must install Residual Target less than 1.E4 (1.E5 or 1.E6)?


July 13, 2010, 08:56 

#16 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 11,567
Rep Power: 90 
Converge as tight as you need to get the accuracy you want.


Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
how to compute relative velocity from absolute?  spk  Main CFD Forum  3  July 9, 2010 08:42 
sormon.f usage for fixing a constant velocity for defined cellset  Tilak  STARCD  0  November 1, 2009 08:06 
wall boundary condition with constant velocity  Rogerio Fernandes Brito  CFX  0  August 17, 2008 10:01 
About create new material  jasonchang  CFX  3  May 18, 2006 21:07 
Neumann pressure BC and velocity field  Antech  Main CFD Forum  0  April 25, 2006 02:15 