# Constant velocity of the material

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 July 8, 2010, 12:03 Constant velocity of the material #1 New Member   Join Date: May 2010 Posts: 21 Rep Power: 8 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: 10 ...Come again?

 July 9, 2010, 06:04 #3 New Member   Join Date: May 2010 Posts: 21 Rep Power: 8 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: 12,707 Rep Power: 98 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
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Quote:
 Originally Posted by ghorrocks Usually you want a velocity inlet and a pressure outlet.
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: 10 Is "z" the center-line 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
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Quote:
 Originally Posted by Josh Is "z" the center-line velocity? Could you give us some more information about the simulation? Maybe you could post a picture of the domain, mesh, etc.
here is a file .res
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: 10 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
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Quote:
 Originally Posted by Josh Unfortunately, I'm away from the office until July 19 and don't have access to CFX. Sorry, Sas.
well I'll wait

 July 11, 2010, 07:37 #10 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,707 Rep Power: 98 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
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Quote:
 Originally Posted by ghorrocks 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.
.res file
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: 12,707 Rep Power: 98 It does not let me download it. Can you post the CCL on the forum?

July 12, 2010, 10:14
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Quote:
 Originally Posted by ghorrocks It does not let me download it. Can you post the CCL on the forum?
Сan be load on rapidshare?

# State file created: 2010/07/12 19:41:56
# CFX-12.0.1 build 2009.04.14-23.02

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 SP-273 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 SP-273 format.
END
MATERIAL GROUP: IAPWS IF97
Group Description = Liquid, vapour and binary mixture materials which use \
the IAPWS IF-97 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 SP-273 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 SP-273 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 = 1.831E-05 [kg m^-1 s^-1]
Option = Value
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 2.61E-2 [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 = 1.831E-05 [kg m^-1 s^-1]
Option = Value
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 2.61E-02 [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 = 8.899E-4 [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 = 2.57E-04 [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 = 9.4E-06 [kg m^-1 s^-1]
Option = Value
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 193E-04 [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.E-4
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: 12,707 Rep Power: 98 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
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Join Date: May 2010
Posts: 21
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Quote:
 Originally Posted by ghorrocks 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.
that is, as I understand you must install Residual Target less than 1.E-4 (1.E-5 or 1.E-6)?

 July 13, 2010, 08:56 #16 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 12,707 Rep Power: 98 Converge as tight as you need to get the accuracy you want.

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