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drew July 11, 2007 12:33

wall velocity not zero
 
Hello,

I am using an axial symmetric 2d mesh in ANSYS 10. The wall is no-slip. The working fluid is Air at 25 C. The velocity at the wall is not zero at the inlet and outlet. I tried using the hybrid option in Post but it still was not zero. Any ideas? Thanks.

Drew

drew July 19, 2007 14:08

Re: wall velocity not zero
 
I don't know if this will help but here is the command, the mesh, and the velocity profile at the opening. You can see that the velocity is not zero at the wall. The same problem happens at the inlet.

LIBRARY:

CEL:

EXPRESSIONS:

velocity = 2.65258[m*s^-1]*(1-(x^2+y^2)/(400E-6[m])^2)

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 = 1.831E-05 [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

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

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

Specific Heat Capacity = 1.0044E+03 [J kg^-1 K^-1]

Specific Heat Type = Constant Pressure

END

THERMAL CONDUCTIVITY:

Option = Value

Thermal Conductivity = 2.61E-02 [W m^-1 K^-1]

END

END

END END FLOW:

SOLUTION UNITS:

Angle Units = [rad]

Length Units = [m]

Mass Units = [kg]

Solid Angle Units = [sr]

Temperature Units = [K]

Time Units = [s]

END

SIMULATION TYPE:

Option = Steady State

EXTERNAL SOLVER COUPLING:

Option = None

END

END

DOMAIN: Domain 1

Coord Frame = Coord 0

Domain Type = Fluid

Fluids List = Air at 25 C

Location = B13

BOUNDARY: inlet

Boundary Type = INLET

Location = inlet

BOUNDARY CONDITIONS:

FLOW REGIME:

Option = Subsonic

END

MASS AND MOMENTUM:

Normal Speed = velocity

Option = Normal Speed

END

END

END

BOUNDARY: opening

Boundary Type = OPENING

Location = opening

BOUNDARY CONDITIONS:

FLOW REGIME:

Option = Subsonic

END

MASS AND MOMENTUM:

Option = Static Pressure for Entrainment

Relative Pressure = 0 [Pa]

END

END

END

BOUNDARY: sym1

Boundary Type = SYMMETRY

Location = sym1

END

BOUNDARY: sym2

Boundary Type = SYMMETRY

Location = sym2

END

BOUNDARY: wall

Boundary Type = WALL

Location = wall

BOUNDARY CONDITIONS:

WALL INFLUENCE ON FLOW:

Option = No Slip

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 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 = 400

Timescale Control = Auto Timescale

Timescale Factor = 1.0

END

CONVERGENCE CRITERIA:

Residual Target = 0.000001

Residual Type = RMS

END

DYNAMIC MODEL CONTROL:

Global Dynamic Model Control = On

END

END END COMMAND FILE:

Version = 11.0

Results Version = 11.0 END EXECUTION CONTROL:

INTERPOLATOR STEP CONTROL:

Runtime Priority = Standard

EXECUTABLE SELECTION:

Double Precision = Off

END

MEMORY CONTROL:

Memory Allocation Factor = 1.0

END

END

PARALLEL HOST LIBRARY:

HOST DEFINITION: dolve20103

Host Architecture String = intel_xeon64.sse2_winnt5.1

Installation Root = C:\Program Files\ANSYS Inc\v%v\CFX

END

END

PARTITIONER STEP CONTROL:

Multidomain Option = Independent Partitioning

Runtime Priority = Standard

EXECUTABLE SELECTION:

Use Large Problem Partitioner = Off

END

MEMORY CONTROL:

Memory Allocation Factor = 1.0

END

PARTITIONING TYPE:

MeTiS Type = k-way

Option = MeTiS

Partition Size Rule = Automatic

END

END

RUN DEFINITION:

Definition File = C:/Temp/nozzle/nozzle400.def

Interpolate Initial Values = Off

Run Mode = Full

END

SOLVER STEP CONTROL:

Runtime Priority = Standard

EXECUTABLE SELECTION:

Double Precision = Off

END

LICENSE CONTROL:

Preferred License = 178

Shared License Port = 1958

END

MEMORY CONTROL:

Memory Allocation Factor = 1.0

END

PARALLEL ENVIRONMENT:

Number of Processes = 1

Start Method = Serial

END

END END

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drew July 20, 2007 15:24

Re: wall velocity not zero
 
This is a zoomed in view of the velocity profile at the outlet after using the hybrid option. Is there something I can change at the boundary condition to correct this?

http://img490.imageshack.us/img490/9...tledmk8.th.jpgwww.ImageShack.us" /></a>

Drew


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