[ghorrocks]

Have you read through this?

http://www.cfd-online.com/Wiki/Ansys...gence_criteria

[saini.yashwant]

Originally Posted by sivarama1

Hi all,
i am simulating wind turbine ,but here converging problem,any body verify my boundary conditions,is it i was given correct or not.


Setting up CFX Solver run ...


+--------------------------------------------------------------------+
| |
| CFX Command Language for Run |
| |
+--------------------------------------------------------------------+

LIBRARY:
CEL:
EXPRESSIONS:
dt = 0.04 [s]
END
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
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:
Molar Mass = 28.96 [kg kmol^-1]
Option = Ideal Gas
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-2 [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 = Transient
EXTERNAL SOLVER COUPLING:
Option = None
END
INITIAL TIME:
Option = Automatic with Value
Time = 0 [s]
END
TIME DURATION:
Option = Total Time
Total Time = 300.0*dt
END
TIME STEPS:
Option = Timesteps
Timesteps = dt
END
END
DOMAIN: rotordisc
Coord Frame = Coord 0
Domain Type = Fluid
Fluids List = Air Ideal Gas
Location = turbine Assembly,turbine Assembly 2
BOUNDARY: discback Side 1
Boundary Type = INTERFACE
Location = DISKOUTLET,DISKOUTLET 2
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: frontdisc Side 2
Boundary Type = INTERFACE
Location = DISKINLET,DISKINLET 2
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: outerdisc Side 1
Boundary Type = INTERFACE
Location = SHROUD 2,SHROUD
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: per1 Side 1
Boundary Type = INTERFACE
Location = PER1
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: per1 Side 2
Boundary Type = INTERFACE
Location = PER2 2
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: per2 Side 1
Boundary Type = INTERFACE
Location = PER1 2
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: per2 Side 2
Boundary Type = INTERFACE
Location = PER2
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: rotordisc Default
Boundary Type = WALL
Frame Type = Rotating
Location = BLADE,BLADE 2,HUB,HUB 2
BOUNDARY CONDITIONS:
WALL INFLUENCE ON FLOW:
Option = No Slip
END
END
END
DOMAIN MODELS:
BUOYANCY MODEL:
Option = Non Buoyant
END
DOMAIN MOTION:
Alternate Rotation Model = On
Angular Velocity = 71.9 [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 MODELS:
COMBUSTION MODEL:
Option = None
END
HEAT TRANSFER MODEL:
Fluid Temperature = 283.15 [K]
Option = Isothermal
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Option = SST
END
TURBULENT WALL FUNCTIONS:
Option = Automatic
END
END
INITIALISATION:
Coord Frame = Coord 0
Frame Type = Rotating
Option = Automatic
INITIAL CONDITIONS:
Velocity Type = Cylindrical
CYLINDRICAL VELOCITY COMPONENTS:
Option = Automatic with Value
Velocity Axial Component = 10 [m s^-1]
Velocity Theta Component = 0 [m s^-1]
Velocity r Component = 0 [m s^-1]
END
K:
Fractional Intensity = 0.05
Option = Automatic with Value
END
OMEGA:
Option = Automatic
END
STATIC PRESSURE:
Option = Automatic with Value
Relative Pressure = 101325 [Pa]
END
END
END
END
DOMAIN: tunnel
Coord Frame = Coord 0
Domain Type = Fluid
Fluids List = Air Ideal Gas
Location = tunnel Assembly
BOUNDARY: discback Side 2
Boundary Type = INTERFACE
Location = F521.452,F519.452
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: frontdisc Side 1
Boundary Type = INTERFACE
Location = F516.452,F518.452
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: inlet
Boundary Type = INLET
Location = inlet
BOUNDARY CONDITIONS:
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Normal Speed = 10 [m s^-1]
Option = Normal Speed
END
TURBULENCE:
Option = High Intensity and Eddy Viscosity Ratio
END
END
END
BOUNDARY: outerdisc Side 2
Boundary Type = INTERFACE
Location = F515.452,F517.452
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: outlet
Boundary Type = OUTLET
Location = outlet
BOUNDARY CONDITIONS:
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Option = Average Static Pressure
Relative Pressure = 0 [Pa]
END
PRESSURE AVERAGING:
Option = Average Over Whole Outlet
END
END
END
BOUNDARY: tunnel Default
Boundary Type = WALL
Location = \
F522.452,F524.452,F525.452,F526.452,F527.452,F528. 452,F529.452,F530.4\
52,F531.452,F532.452,F541.452,F551.452
BOUNDARY CONDITIONS:
WALL INFLUENCE ON FLOW:
Option = No Slip
END
END
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 = 283.15 [K]
Option = Isothermal
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Option = SST
END
TURBULENT WALL FUNCTIONS:
Option = Automatic
END
END
INITIALISATION:
Coord Frame = Coord 0
Option = Automatic
INITIAL CONDITIONS:
Velocity Type = Cartesian
CARTESIAN VELOCITY COMPONENTS:
Option = Automatic with Value
U = 10 [m s^-1]
V = 0 [m s^-1]
W = 0 [m s^-1]
END
K:
Fractional Intensity = 0.05
Option = Automatic with Value
END
OMEGA:
Option = Automatic
END
STATIC PRESSURE:
Option = Automatic with Value
Relative Pressure = 101325 [Pa]
END
END
END
END
DOMAIN INTERFACE: discback
Boundary List1 = discback Side 1
Boundary List2 = discback Side 2
Interface Type = Fluid Fluid
INTERFACE MODELS:
Option = General Connection
FRAME CHANGE:
Option = Transient Rotor Stator
END
PITCH CHANGE:
Option = None
END
END
MESH CONNECTION:
Option = GGI
END
END
DOMAIN INTERFACE: frontdisc
Boundary List1 = frontdisc Side 1
Boundary List2 = frontdisc Side 2
Interface Type = Fluid Fluid
INTERFACE MODELS:
Option = General Connection
FRAME CHANGE:
Option = Transient Rotor Stator
END
PITCH CHANGE:
Option = None
END
END
MESH CONNECTION:
Option = GGI
END
END
DOMAIN INTERFACE: outerdisc
Boundary List1 = outerdisc Side 1
Boundary List2 = outerdisc Side 2
Interface Type = Fluid Fluid
INTERFACE MODELS:
Option = General Connection
FRAME CHANGE:
Option = Transient Rotor Stator
END
PITCH CHANGE:
Option = None
END
END
MESH CONNECTION:
Option = GGI
END
END
DOMAIN INTERFACE: per1
Boundary List1 = per1 Side 1
Boundary List2 = per1 Side 2
Interface Type = Fluid Fluid
INTERFACE MODELS:
Option = General Connection
FRAME CHANGE:
Option = None
END
PITCH CHANGE:
Option = None
END
END
MESH CONNECTION:
Option = Automatic
END
END
DOMAIN INTERFACE: per2
Boundary List1 = per2 Side 1
Boundary List2 = per2 Side 2
Interface Type = Fluid Fluid
INTERFACE MODELS:
Option = General Connection
FRAME CHANGE:
Option = None
END
PITCH CHANGE:
Option = None
END
END
MESH CONNECTION:
Option = GGI
END
END
OUTPUT CONTROL:
RESULTS:
File Compression Level = Default
Option = Standard
END
TRANSIENT RESULTS: Transient Results 1
File Compression Level = Default
Option = Standard
Output Boundary Flows = All
OUTPUT FREQUENCY:
Option = Timestep Interval
Timestep Interval = 101
END
END
END
SOLVER CONTROL:
ADVECTION SCHEME:
Option = High Resolution
END
CONVERGENCE CONTROL:
Maximum Number of Coefficient Loops = 10
Minimum Number of Coefficient Loops = 3
Timescale Control = Coefficient Loops
END
CONVERGENCE CRITERIA:
Conservation Target = 0.01
Residual Target = 1.E-4
Residual Type = RMS
END
TRANSIENT SCHEME:
Option = Second Order Backward Euler
TIMESTEP INITIALISATION:
Option = Automatic
END
END
END
END
COMMAND FILE:
Results Version = 11.0
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: sivaram
Installation Root = C:\Program Files\Ansys Inc\v%v\CFX
Host Architecture String = amd_opteron.sse2_winnt5.1
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 = D:/tutorial/CFX/wind_3blade3_002_001.def
Initial Values File = D:/tutorial/CFX/wind_3blade2_002_001.res
Interpolate Initial Values = Off
Run Mode = Full
END
SOLVER STEP CONTROL:
Runtime Priority = Standard
EXECUTABLE SELECTION:
Double Precision = Off
END
MEMORY CONTROL:
Memory Allocation Factor = 1.0
END
PARALLEL ENVIRONMENT:
Number of Processes = 1
Start Method = Serial
END
END
END

hi sir,
can u send me the boundary conditions which u applied in cfx so i can try the solution in cfx too.

[mohammad]

Originally Posted by ghorrocks

Hi,

But assuming each blade is equally loaded then the total power is simply n times the power of one blade, regardless of how much power additional blades actually add.

Also you may find the turbo machinery macro in CFD-Post useful in post-processing this.

Glenn Horrocks

Dear Glenn,
Although the original thread looks outdated, but when I read your answer and Suraj's reasons, I became confused that Suraj is right somewhat, and you 100%. Because the blades will be equally loaded in axial steady case ,but the points that Suraj says also make sense.

Do you have any solution for this contradiction or you just say"REGARDLESS" what the real/theoretical results are... it will be "n" times the results of single blade. Then, if you confirm the previous answer what is the cause of this HUGE difference between this two...? and PLZ remember than Suraj's points are in contradiction with energy conservation law...

TNX

[ghorrocks]

My point was simply that for even blade loading, each blade supplies 1/n of the torque. I said nothing about how much extra torque you get by adding more blades. That is a different question so don't get confused.

[drsattar]

Hi for all
I am trying to simulate 5 MW offshore wind turbine (aerodynamics study only) using CFX to validate my results which were coming from another solver, under these conditions
· Full scale of 5 MW offshore wind turbine dimensions
· transient analysis
· Inlet velocity = 9 m/sec
· 3 blade rotor + hub (rotating domain) with angular velocity =1.08 rad/sec
· Nacelle + tower (stationary domain)
· Then, three interfaces have been defined between the stationary domain and the rotating domain due to changes in reference frames. In order to rotate the rotor in ANSYS.
· I create appropriate and suitable meshes for all the parts in ICEM and CFX is specifying domains, boundary conditions, type of analysis, interfaces, etc.

But I always I find this error

First side of interface |
| Domain Interface 1 |
| seems to contain a vertex at R=0 (Rmin/Rrange < GGI ETA TOLERANCE).|
| This is not supported with |
| PITCH CHANGE/Option = Automatic |
| Please use |
| PITCH CHANGE/Option = None |
| instead. |
+--------------------------------------------------------------------+
+--------------------------------------------------------------------+
| ********* WARNING ********* |
| Coordinate transformation of interface |
| Domain Interface 2 |
| into a radial interface resulted in some faces with a very small |
| axial extent. There are two possible reasons for this: |
| 1. The interface contains axial faces (normal to the axis). |
| If this is the case, please split the interface into two parts, |
| so that the purely axial sections could be transformed |
| properly. The transformation type (axial or radial) is chosen |
| automatically based on the largest interface extent. |
| 2. This message may be generated because of a tolerancing issue |
| when the mesh resolution in the axial direction is very |
| small (e.g. at the hub or shroud). If this is the case, you |
| may ignore this message. |
+--------------------------------------------------------------------+
+--------------------------------------------------------------------+
| ERROR #001100279 has occurred in subroutine ErrAction. |
| Message: |
| ****** FATAL ERROR ****** The orthographic view transformation fa- |
| iled on domain interface "Domain Interface 2". Failure may be du- |
| e to r=0 included in transformed cylindrical coordinates of an in- |
| terface with rotational relative motion. Another reason could be |
| that the interface contains faces that are parallel and others t- |
| hat are perpendicular to the rotation axis. |
+--------------------------------------------------------------------+


</SPAN>

When I selected (PITCH CHANGE/Option = Automatic ) which I thought is correct chose but the above error will appear
And when I selected (PITCH CHANGE/Option = None) the run continue and complete, everything is ok, but the values of torque is negative ????
thanks

[ghorrocks]

It looks like you are modelling the whole thing so you are correct to use pitch change=none. As for the negative torque, have you checked the vector direction of the torque?

[drsattar]

hi

do you means that, by using the right hand rule can i find the torque direction
thanks

[ghorrocks]

Just had a look at the torque function in the CFX reference manual. If you use the torque_x, torque_y, torque_z functions it returns the torque about the X, Y and Z coordinate axis respectively (and yes you can use the RH rule to get the direction). But the axis specification is optional and it is not clear what axis it uses if you just use the torque function with no axis defined.

Does anybody know what axis the torque function uses if no axis is defined?

To get around this I would just use the torque_x/y/z functions so you know exactly what axis it is using.

[drsattar]

thanks for your answer
but I calculate the torque of the rotor on the rotation axis

torque_x()@BLADE +torque_x()@BLADE1 +torque_x()@BLADE2

which appear for me negative despite of the rotation of the blades counter-clockwise

[ghorrocks]

To get the correct result in a rotating machine simulation, you need to not only get the numerics correct, but you also need to get the operating point correct. This means that the rotation speed might be a little faster or slower.

So negative torque means the rotation speed is slower - assuming your simulation is accurate.

[drsattar]

can I give a negative value for the rotation speed
for the rotational domain

and I checked some of paper that use the same rotational speed with the same dimension of my wind turbine and got a positive value of torque

[mohammad]

Originally Posted by drsattar

can I give a negative value for the rotation speed
for the rotational domain

and I checked some of paper that use the same rotational speed with the same dimension of my wind turbine and got a positive value of torque

Yeah, you can do it In CFX

[drsattar]

thanks again you are so helpful
and I will try to do simulation with -1.08 rad/s

[raj.singh]

hi,
i m trying to simulate a helical turbine but i only know the inlet velocity.so how to perform transient analysis? of it.Do i need to take two domain one stationary and one rotating?plz suggest something

[ghorrocks]

You will need to know a pressure somewhere to set the pressure level.

Look at the CFX tutorials for how to run simulations.

And in future, if you have a new question start a new thread rather than hijacking an old thread.

[hossam elbakry]

hello,
i am using fluent 15, after i draw the horizontal turbine using solidworks,
i made a run of fluent with omega and input wind speed, using k-omega sst model,
the resultant torque multiplied with the omega to get the power.
the question is: the calculated power using ansys can be compared with the net power of commercial turbine directly, "
or should be multiplied to rotor efficiency first before comparing with net power of commercial turbine?

[ghorrocks]

The power at the rotor shaft (torque x omega) should match the torque at the rotor shaft of the turbine.

[hossam elbakry]

but i am not comparing with torque at the rotor shaft of the turbine,,,
i am comparing power from ansys ( omega x torque) with the net producing power from the generator where the commercial turbine connected to.
so i think that a parameter of efficiency of rotor and generator and inverter should be included.

[k.vafiadis]

You can only compare the CFD computed rotor power to the rotor power of the real machine. If it's not possible to find the real rotor's power, you may need to find it by either experiment (if it's possible) or by asking the manufacturer.
If you know the efficiency of the generator, etc, you should try to use it to make an approximation of the net aerodynamic rotor power.

[hossam elbakry]

you are correct,,,i am trying to compare the ansys power (torque x omega) with the generator power ,,,,but i think the rotor efficicency and inverter efficiency and generator efficiency should be included,,
am i right?