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October 28, 2007, 04:14 |
RPM in Wind Turbine
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#1 |
Guest
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Hi All!
In my previous work I have done some Rotating domain steady state solutions.But for wind turbines i have no ideas of setting up Boundary conditions.In some references i got velocity inlet,constant pressure outlet and no slip walls. But i needs the rpm,How should i specify it? Does it need a time bounded(transient) run? Thanks in advance for your clues. Pankaj. |
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October 29, 2007, 05:56 |
can anybody help me out?
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#2 |
Guest
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I am realy stuck with the problem of how to define RPM.
Can anybody help me out? |
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October 29, 2007, 17:44 |
Re: can anybody help me out?
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#3 |
Guest
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Hi,
Read the manual about rotating frames of reference. You can probably use a frozen rotor/stator approach so you don't need to model the full transient effects. This will be heaps quicker than a full transient simulation. Glenn Horrocks |
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October 31, 2007, 14:12 |
Re: can anybody help me out?
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#4 |
Guest
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Hi
It is a flow driven problem, the rpm will be defined by software itself. My question comes to the torque load from the generator, how to define this? Is it a correct way to do it: -to assume a group of different torque value to get a performace curve (Torque-RPM) and then -to match the generator? Or there are other way to do it? Thanks Ahlo |
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November 1, 2007, 05:32 |
Re: can anybody help me out?
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#5 |
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Hi,
Read the Best practices guide for turbo machinery in the documentation. I think there is one on cavitation which discusses generating pummp curves too, that may be useful. Glenn Horrocks |
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November 6, 2007, 23:32 |
Re: can anybody help me out?
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#6 |
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I have the same problem analyzing a Savonius Rotor (VAWT)
I'm not sure if i'am in the right way... I have been using CFdesign and it has an option called "flow-driven motion". You only need to specify the inertia of the rotor (fluid zone with the rotor) and a resistive torque that opposes to the rotation. Once you analyze the model (transient analysis) you can obtain the RPM (this will depend on the Torque that you choose, if it is too big the rotor will not move) In this case you can obtain the power by multiplying the specified Torque with the RPMs that the rotor reaches. As Ahlo said (I'm analyzing like him) you can vary the resistive torque and obtain the optimum performance. Then you need to choose a generator that match the optimum torque. Of course the analysis is made at a specific wind speed, so it will be the optimum at the specified wind speed. Any suggestion? is there a way of obtaining the RPMs with a steady analysis. |
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November 20, 2009, 12:22 |
Same problem
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#7 |
New Member
Join Date: Nov 2009
Posts: 1
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I'm currently using CFDesign, but we are thinking about moving to ansys. How would you set up a flow driven turbine in Ansys CFX as stated?
"I have been using CFdesign and it has an option called "flow-driven motion". You only need to specify the inertia of the rotor (fluid zone with the rotor) and a resistive torque that opposes to the rotation. Once you analyze the model (transient analysis) you can obtain the RPM (this will depend on the Torque that you choose, if it is too big the rotor will not move)" If I can't set up a turbine blade model like this, then there is no way I can move to ansys for CFD as I do a lot of turbine analysis. Any suggestions? I'd really like to see how this is done so I can upgrade to ansys. |
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November 21, 2009, 05:07 |
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#8 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,830
Rep Power: 144 |
This cannot currently be done in CFX. Well, at least it can't be done easily. It is a very commonly requested feature but so far it has not appeared. Try contacting your CFX support person and pushing them for it - eventually CFX will add the feature.
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November 23, 2009, 00:37 |
wind turbine simulation
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#9 |
Member
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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 = 7 [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 k = 0.1875 [m^2 s^-2] 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 = F519.452,F521.452 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 = F518.452,F516.452 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 = 7 [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 = F517.452,F515.452 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 END K: Option = Automatic END OMEGA: Option = Automatic END STATIC PRESSURE: Option = Automatic 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: 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: 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_3d_new.def 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 Ignoring Fractional Intensity for K IC. | | | Solver | | | | | | ANSYS CFX Solver 11.0 | | | | Version 2007.01.15-19.20 Mon Jan 15 19:24:21 GMTST 2007 | | | | Executable Attributes | | | | single-int32-32bit-novc6-optimised-supfort-noprof-nospag-lcomp | | | | Copyright 1996-2007 ANSYS Europe Ltd. | | Job Information | Run mode: serial run Host computer: SIVARAM Job started: Tue Jun 23 11:04:09 2009 | Memory Allocated for Run (Actual usage may be less) | Data Type Kwords Words/Node Words/Elem Kbytes Bytes/Node Real 109379.1 425.67 268.98 427262.1 1702.66 Integer 31344.0 121.98 77.08 122437.5 487.92 Character 2932.5 11.41 7.21 2863.8 11.41 Logical 65.0 0.25 0.16 253.9 1.01 Double 1208.0 4.70 2.97 9437.5 37.61 | Mesh Statistics | Domain Name : rotordisc Total Number of Nodes = 201532 Total Number of Elements = 186990 Total Number of Hexahedrons = 186990 Total Number of Faces = 28664 Minimum Orthogonality Angle [degrees] = 9.2 ! Maximum Aspect Ratio = 150.4 ok Maximum Mesh Expansion Factor = 1071.9 ! Domain Name : tunnel Total Number of Nodes = 55428 Total Number of Elements = 219652 Total Number of Tetrahedrons = 173432 Total Number of Prisms = 46051 Total Number of Pyramids = 169 Total Number of Faces = 10224 Minimum Orthogonality Angle [degrees] = 28.2 ok Maximum Aspect Ratio = 23.6 OK Maximum Mesh Expansion Factor = 46.0 ! Global Statistics : Global Number of Nodes = 256960 Global Number of Elements = 406642 Total Number of Tetrahedrons = 173432 Total Number of Prisms = 46051 Total Number of Hexahedrons = 186990 Total Number of Pyramids = 169 Global Number of Faces = 38888 Minimum Orthogonality Angle [degrees] = 9.2 ! Maximum Aspect Ratio = 150.4 ok Maximum Mesh Expansion Factor = 1071.9 ! Domain Interface Name : per1 Non-overlap area fraction on side 1 = 0.00E+00 Non-overlap area fraction on side 2 = 0.00E+00 Domain Interface Name : per2 Non-overlap area fraction on side 1 = 0.00E+00 Non-overlap area fraction on side 2 = 0.00E+00 | | | FATAL ERROR : | | | | Initial values are required for all variables in TRANSIENT runs. | | In this simulation, no initial value was set for | | | | Variable : Pressure | | Domain : tunnel | | | | The value can be set using the Initial Values panel in CFX Pre. | | | | To bypass this message and use default solver initial values, | | set the expert parameter "transient initialisation override = t" | | | | An error has occurred in cfx5solve: | | | | The ANSYS CFX solver has terminated without writing a results | | file. Command on host sivaram exited with return code 0. | End of solution stage. | The following user files have been saved in the directory | | D:\tutorial\CFX\wind_3d_new_006: | | | | mon |
__________________
sivaramakrihnaiah |
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November 23, 2009, 04:05 |
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#10 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,830
Rep Power: 144 |
And your question is ......?
I trust you are not going to ask "Why did this run stop?". The answer to that is bleedingly obvious and the error message tells you exactly what you need to do. And while you are at it, check your mesh - an expansion factor of 1079 is pretty bad. |
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