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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.

Code:

``` 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```
http://img374.imageshack.us/my.php?i...400meshns2.jpg

http://img383.imageshack.us/my.php?i...yprofilin2.jpg

 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/my.php?i...ntitledmk8.jpg

Drew

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