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Centrifugal fan-reverse flow in outlet lesds to a mass in flow field

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Old   March 29, 2017, 06:30
Default Centrifugal fan-reverse flow in outlet lesds to a mass in flow field
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Hi, i am try to simulate a centrifugal fan, and try to estimate the effiency (just only impeller, so i add a former extention and a latter one, just can see in the images).
inlet is massflow(rated flow),outlet is static pressure, the number of fans is 17.
question is :along the solving process,in the early iterations,the result seems just OK,and the RMS decrease. but with the iteratons increase,the solver manager show that a reverse flow in the outlet,and always exsisting,and the RMS tendency becomes unstable,the flow field of result is unsymmetric.
i have tried to change the outlet to opening, and change to a high quality mesh and so on,but the problem always existing.
i really want to know is this phenomenon is just normal exsisting or just the numerical problem(somewhere i am wrong).
thanks a lot!
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Old   March 29, 2017, 06:33
Default here my CEL
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LIBRARY:
CEL:
EXPRESSIONS:
NJ = torque_z()@R2 Blade+torque_z()@R2 Hub+torque_z()@R2 Shroud
desty = 4.003[g/mol]*Absolute Pressure /(R*Temperature )
dp = massFlowAve(Total Pressure in Stn Frame )@S2 \
Outlet-massFlowAve(Total Pressure in Stn Frame )@s1inlet
END
END
MATERIAL: he
Material Group = User
Option = Pure Substance
Thermodynamic State = Gas
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Molar Mass = 4.003 [kg kmol^-1]
Option = Ideal Gas
END
SPECIFIC HEAT CAPACITY:
Option = Value
Specific Heat Capacity = 5189.4 [J kg^-1 K^-1]
Specific Heat Type = Constant Pressure
END
REFERENCE STATE:
Option = Specified Point
Reference Pressure = 7 [MPa]
Reference Specific Enthalpy = 2744337.8 [J kg^-1]
Reference Specific Entropy = 22105.7 [J kg^-1 K^-1]
Reference Temperature = 250 [C]
END
DYNAMIC VISCOSITY:
Dynamic Viscosity = 0.00003 [Pa s]
Option = Value
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 0.2333 [W m^-1 K^-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: R2
Coord Frame = Coord 0
Domain Type = Fluid
Location = Entire Passage
BOUNDARY: R2 Blade
Boundary Type = WALL
Frame Type = Rotating
Location = Entire BLADE
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Option = Adiabatic
END
MASS AND MOMENTUM:
Option = No Slip Wall
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
END
BOUNDARY: R2 Hub
Boundary Type = WALL
Frame Type = Rotating
Location = Entire HUB
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Option = Adiabatic
END
MASS AND MOMENTUM:
Option = No Slip Wall
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
END
BOUNDARY: R2 Shroud
Boundary Type = WALL
Frame Type = Rotating
Location = Entire SHROUD
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Option = Adiabatic
END
MASS AND MOMENTUM:
Option = No Slip Wall
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
END
BOUNDARY: r2 to s2 Side 1
Boundary Type = INTERFACE
Location = Entire OUTFLOW
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Option = Conservative Interface Flux
END
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: s1 to r2 Side 1 1
Boundary Type = INTERFACE
Location = Entire INFLOW
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Option = Conservative Interface Flux
END
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
DOMAIN MODELS:
BUOYANCY MODEL:
Option = Non Buoyant
END
DOMAIN MOTION:
Alternate Rotation Model = true
Angular Velocity = 4000 [rev min^-1]
Option = Rotating
AXIS DEFINITION:
Option = Coordinate Axis
Rotation Axis = Coord 0.3
END
END
MESH DEFORMATION:
Option = None
END
REFERENCE PRESSURE:
Reference Pressure = 1 [atm]
END
END
FLUID DEFINITION: He Ideal Gas
Material = he
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
HEAT TRANSFER MODEL:
Include Viscous Work Term = True
Option = Total Energy
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Option = k epsilon
END
TURBULENT WALL FUNCTIONS:
High Speed Model = Off
Option = Scalable
END
END
END
DOMAIN: S2
Coord Frame = Coord 0
Domain Type = Fluid
Location = HFLUID
BOUNDARY: S2 Outlet
Boundary Type = OPENING
Location = HOUTLET
BOUNDARY CONDITIONS:
FLOW REGIME:
Option = Subsonic
END
HEAT TRANSFER:
Option = Static Temperature
Static Temperature = 530 [K]
END
MASS AND MOMENTUM:
Option = Entrainment
Relative Pressure = 7.2 [MPa]
PRESSURE OPTION:
Option = Static Pressure
END
END
TURBULENCE:
Option = Zero Gradient
END
END
END
BOUNDARY: r2 to s2 Side 2
Boundary Type = INTERFACE
Location = HINLET
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Option = Conservative Interface Flux
END
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: s2updown
Boundary Type = WALL
Location = HDOWNFACE,HUPFACE
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Option = Adiabatic
END
MASS AND MOMENTUM:
Option = Free Slip Wall
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: He Ideal Gas
Material = he
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
HEAT TRANSFER MODEL:
Include Viscous Work Term = True
Option = Total Energy
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Option = k epsilon
END
TURBULENT WALL FUNCTIONS:
High Speed Model = Off
Option = Scalable
END
END
END
DOMAIN: s1
Coord Frame = Coord 0
Domain Type = Fluid
Location = FFLUID
BOUNDARY: s1 to r2 Side 2 1
Boundary Type = INTERFACE
Location = FOUTLET
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Option = Conservative Interface Flux
END
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: s1cemian
Boundary Type = WALL
Location = FCEMAIN
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Option = Adiabatic
END
MASS AND MOMENTUM:
Option = Free Slip Wall
END
END
END
BOUNDARY: s1inlet
Boundary Type = INLET
Location = FINLET
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Normal to Boundary Condition
END
FLOW REGIME:
Option = Subsonic
END
HEAT TRANSFER:
Option = Static Temperature
Static Temperature = 250 [C]
END
MASS AND MOMENTUM:
Mass Flow Rate = 96 [kg s^-1]
Mass Flow Rate Area = As Specified
Option = Mass Flow Rate
END
TURBULENCE:
Option = Zero Gradient
END
END
END
BOUNDARY: s1solid
Boundary Type = WALL
Location = FSOLID
BOUNDARY CONDITIONS:
HEAT TRANSFER:
Option = Adiabatic
END
MASS AND MOMENTUM:
Option = No Slip Wall
WALL VELOCITY:
Angular Velocity = 4000 [rev min^-1]
Option = Rotating Wall
AXIS DEFINITION:
Option = Coordinate Axis
Rotation Axis = Coord 0.3
END
END
END
WALL ROUGHNESS:
Option = Smooth Wall
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: He Ideal Gas
Material = he
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
HEAT TRANSFER MODEL:
Include Viscous Work Term = True
Option = Total Energy
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Option = k epsilon
END
TURBULENT WALL FUNCTIONS:
High Speed Model = Off
Option = Scalable
END
END
END
DOMAIN INTERFACE: r2 to s2
Boundary List1 = r2 to s2 Side 1
Boundary List2 = r2 to s2 Side 2
Interface Type = Fluid Fluid
INTERFACE MODELS:
Option = General Connection
FRAME CHANGE:
Option = Frozen Rotor
END
MASS AND MOMENTUM:
Option = Conservative Interface Flux
MOMENTUM INTERFACE MODEL:
Option = None
END
END
PITCH CHANGE:
Option = Specified Pitch Angles
Pitch Angle Side1 = 360 [degree]
Pitch Angle Side2 = 360 [degree]
END
END
MESH CONNECTION:
Option = GGI
END
END
DOMAIN INTERFACE: s1 to r2
Boundary List1 = s1 to r2 Side 1 1
Boundary List2 = s1 to r2 Side 2 1
Interface Type = Fluid Fluid
INTERFACE MODELS:
Option = General Connection
FRAME CHANGE:
Option = Frozen Rotor
END
MASS AND MOMENTUM:
Option = Conservative Interface Flux
MOMENTUM INTERFACE MODEL:
Option = None
END
END
PITCH CHANGE:
Option = Specified Pitch Angles
Pitch Angle Side1 = 360 [degree]
Pitch Angle Side2 = 360 [degree]
END
END
MESH CONNECTION:
Option = GGI
END
END
OUTPUT CONTROL:
BACKUP RESULTS: Backup Results 1
Extra Output Variables List = Absolute Pressure
File Compression Level = Default
Option = Standard
Output Equation Residuals = All
OUTPUT FREQUENCY:
Iteration Interval = 100
Option = Iteration Interval
END
END
MONITOR OBJECTS:
MONITOR BALANCES:
Option = Full
END
MONITOR FORCES:
Option = Full
END
MONITOR PARTICLES:
Option = Full
END
MONITOR POINT: niuju
Coord Frame = Coord 0
Expression Value = NJ
Option = Expression
END
MONITOR POINT: ych
Coord Frame = Coord 0
Expression Value = dp
Option = Expression
END
MONITOR RESIDUALS:
Option = Full
END
MONITOR TOTALS:
Option = Full
END
END
RESULTS:
File Compression Level = Default
Option = Standard
END
END
SOLVER CONTROL:
Turbulence Numerics = High Resolution
ADVECTION SCHEME:
Option = High Resolution
END
CONVERGENCE CONTROL:
Length Scale Option = Conservative
Maximum Number of Iterations = 1000000
Minimum Number of Iterations = 1
Timescale Control = Auto Timescale
Timescale Factor = 1
END
CONVERGENCE CRITERIA:
Residual Target = 0.00001
Residual Type = RMS
END
DYNAMIC MODEL CONTROL:
Global Dynamic Model Control = On
END
END
END
COMMAND FILE:
Version = 16.0
Results Version = 16.0
END
SIMULATION CONTROL:
EXECUTION CONTROL:
EXECUTABLE SELECTION:
Double Precision = Yes
END
INTERPOLATOR STEP CONTROL:
Runtime Priority = Standard
MEMORY CONTROL:
Memory Allocation Factor = 1.2
END
END
PARALLEL HOST LIBRARY:
HOST DEFINITION: dellpc
Remote Host Name = DELL-PC
Installation Root = D:\ANSYS16.0\ANSYS Inc\v%v\CFX
Host Architecture String = winnt-amd64
END
END
PARTITIONER STEP CONTROL:
Multidomain Option = Automatic
Runtime Priority = Standard
EXECUTABLE SELECTION:
Use Large Problem Partitioner = Off
END
MEMORY CONTROL:
Memory Allocation Factor = 1.2
END
PARTITION SMOOTHING:
Maximum Partition Smoothing Sweeps = 100
Option = Smooth
END
PARTITIONING TYPE:
MeTiS Type = k-way
Option = MeTiS
Partition Size Rule = Automatic
Partition Weight Factors = 0.10000, 0.10000, 0.10000, 0.10000, \
0.10000, 0.10000, 0.10000, 0.10000, 0.10000, 0.10000
END
END
RUN DEFINITION:
Solver Input File = E:\2017-3-27\wu-yplu-try\66\66_002.res
Run Mode = Full
Solver Results File = E:\2017-3-27\wu-yplu-try\66\66_003.res
END
SOLVER STEP CONTROL:
Runtime Priority = Standard
MEMORY CONTROL:
Memory Allocation Factor = 1.2
END
PARALLEL ENVIRONMENT:
Number of Processes = 10
Start Method = Platform MPI Local Parallel
Parallel Host List = dellpc*10
END
END
END
END
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Old   March 29, 2017, 10:49
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Instead of using those BC, I would use total pressure at the inlet and mass flow rate at the outlet. It is usually recommended when you have rotating domains.
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Old   March 29, 2017, 11:00
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very appreciate for your advice,but i don't know the total pressure in the inlet.(but i've tried static pressure as inlet,and massflow as outlet,also remains the problem), i attached the RMS for you(i thank the later iterations is somewhere wrong)
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centrifugal fan impeller, reverse flow, unsymmetric flow field

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