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Difficulty in calculating angular velocity of Savonius turbine simulation 

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May 17, 2012, 00:02 
Difficulty in calculating angular velocity of Savonius turbine simulation

#1 
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Abdullah Al Faruk
Join Date: Apr 2012
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Dear Friends,
I am trying to simulate Savonius wind turbine using the rigid body solver of ANSYS CFX v13 with sliding mesh of subdomain. How can I calculate angular velocity of rotor and torque on rotor in CFXpost? While calculating the angular velocity in CFXSolver Manager using the rigid body state function (rbstate(Angular Velocity Y)@Rotor), the angular velocity is continuously increasing. Attached is the CCL for run. Please help me . With Thanks Abdullah LIBRARY: CEL: EXPRESSIONS: Air Density = 1.185 [kg m3] AngularVelocity = Circumferential Velocity / 0.159 Power Coefficient = Useful Power / Wind Power Rotor Diameter = 0.32 [m] Rotor Height = 0.64 [m] Rotor Swept Area = Rotor Diameter * Rotor Height Useful Power = Torque on Rotor * AngularVelocity Wind Power = 0.5 * Air Density * Rotor Swept Area * Wind Velocity^3 Wind Velocity = 5 [m s1] END END ADDITIONAL VARIABLE: Additional Variable 1 Option = Definition Tensor Type = SCALAR Units = [radian s1 ] Variable Type = Specific END ADDITIONAL VARIABLE: Useful power Option = Definition Tensor Type = SCALAR Units = [W] Variable Type = Volumetric END COORDINATE FRAME DEFINITIONS: COORDINATE FRAME: Coord 1 Axis 3 Point = 0 [m], 0.3886 [m], 1 [m] Coord Frame Type = Cartesian Option = Axis Points Origin Point = 0 [m], 0.3886 [m], 0 [m] Plane 13 Point = 1 [m], 0.3886 [m], 0 [m] Reference Coord Frame = Coord 0 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 EQUATION OF STATE: Density = 1.185 [kg m^3] Molar Mass = 28.96 [kg kmol^1] Option = Value END SPECIFIC HEAT CAPACITY: Option = Value Specific Heat Capacity = 1.0044E+03 [J kg^1 K^1] Specific Heat Type = Constant Pressure 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 DYNAMIC VISCOSITY: Dynamic Viscosity = 1.831E05 [kg m^1 s^1] Option = Value END THERMAL CONDUCTIVITY: Option = Value Thermal Conductivity = 2.61E02 [W m^1 K^1] END ABSORPTION COEFFICIENT: Absorption Coefficient = 0.01 [m^1] Option = Value END SCATTERING COEFFICIENT: Option = Value Scattering Coefficient = 0.0 [m^1] END REFRACTIVE INDEX: Option = Value Refractive Index = 1.0 [m m^1] END THERMAL EXPANSIVITY: Option = Value Thermal Expansivity = 0.003356 [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 = Transient EXTERNAL SOLVER COUPLING: Option = None END INITIAL TIME: Option = Automatic with Value Time = 0 [s] END TIME DURATION: Option = Total Time Total Time = 35 [s] END TIME STEPS: Option = Timesteps Timesteps = 0.1 [s] END END DOMAIN: Box Domain Coord Frame = Coord 0 Domain Type = Fluid Location = Box BOUNDARY: Default Fluid Fluid Interface Side 1 Boundary Type = INTERFACE Location = B Intface BOUNDARY CONDITIONS: MASS AND MOMENTUM: Option = Conservative Interface Flux END MESH MOTION: Option = Stationary 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 = Wind Velocity Option = Normal Speed END MESH MOTION: Option = Stationary END TURBULENCE: Option = Medium Intensity and Eddy Viscosity Ratio END END END BOUNDARY: outlet Boundary Type = OUTLET Location = Outlet BOUNDARY CONDITIONS: FLOW REGIME: Option = Subsonic END MASS AND MOMENTUM: Option = Static Pressure Relative Pressure = 0 [Pa] END MESH MOTION: Option = Stationary END END END BOUNDARY: walls Boundary Type = WALL Location = B Bottom,B Left,B Right,B Top BOUNDARY CONDITIONS: MASS AND MOMENTUM: Option = No Slip Wall END MESH MOTION: Option = Stationary 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 = Regions of Motion Specified MESH MOTION MODEL: Option = Displacement Diffusion MESH STIFFNESS: Option = Increase near Small Volumes Stiffness Model Exponent = 10 END END END REFERENCE PRESSURE: Reference Pressure = 1 [atm] END END FLUID DEFINITION: Fluid 1 Material = Air at 25 C Option = Material Library MORPHOLOGY: Option = Continuous Fluid 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 = k epsilon END TURBULENT WALL FUNCTIONS: Option = Scalable END END END DOMAIN: Cylinder Domain Coord Frame = Coord 1 Domain Type = Fluid Location = Cylinder BOUNDARY: Cylinder ends Boundary Type = WALL Location = C Top,C Bottom BOUNDARY CONDITIONS: MASS AND MOMENTUM: Option = No Slip Wall END MESH MOTION: Option = Rigid Body Solution Rigid Body = Rotor END WALL ROUGHNESS: Option = Smooth Wall END END END BOUNDARY: Default Fluid Fluid Interface Side 2 Boundary Type = INTERFACE Location = C Intface BOUNDARY CONDITIONS: MASS AND MOMENTUM: Option = Conservative Interface Flux END MESH MOTION: Option = Stationary END TURBULENCE: Option = Conservative Interface Flux END END END BOUNDARY: RotorBody Boundary Type = WALL Location = R 1 Inner,R 1 Outer,R 1 Side 1,R 1 Side 2,R 1 Top,R 2 \ Inner,R 2 Outer,R 2 Side 1,R 2 Side 2,R 2 Top,R Endplate Bottom,R \ Endplate Peripheri,R Endplate Top,R Stand BOUNDARY CONDITIONS: MASS AND MOMENTUM: Option = No Slip Wall END MESH MOTION: Option = Rigid Body Solution Rigid Body = Rotor 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 = Regions of Motion Specified MESH MOTION MODEL: Option = Displacement Diffusion MESH STIFFNESS: Option = Increase near Small Volumes Stiffness Model Exponent = 10 END END END REFERENCE PRESSURE: Reference Pressure = 1 [atm] END END FLUID DEFINITION: Fluid 1 Material = Air at 25 C Option = Material Library MORPHOLOGY: Option = Continuous Fluid 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 = k epsilon END TURBULENT WALL FUNCTIONS: Option = Scalable END END SUBDOMAIN: Blade Coord Frame = Coord 1 Location = Cylinder MESH MOTION: Option = Rigid Body Solution Rigid Body = Rotor END END END DOMAIN INTERFACE: Default Fluid Fluid Interface Boundary List1 = Default Fluid Fluid Interface Side 1 Boundary List2 = Default Fluid Fluid Interface Side 2 Interface Type = Fluid Fluid INTERFACE MODELS: Option = General Connection FRAME CHANGE: Option = None END MASS AND MOMENTUM: Option = Conservative Interface Flux MOMENTUM INTERFACE MODEL: Option = None END END PITCH CHANGE: Option = None END END MESH CONNECTION: Option = GGI END END INITIALISATION: Option = Automatic INITIAL CONDITIONS: Velocity Type = Cartesian CARTESIAN VELOCITY COMPONENTS: Option = Automatic with Value U = 0 [m s^1] V = 0 [m s^1] W = 0 [m s^1] END STATIC PRESSURE: Option = Automatic with Value Relative Pressure = 0 [Pa] END TURBULENCE INITIAL CONDITIONS: Option = Medium Intensity and Eddy Viscosity Ratio END END END OUTPUT CONTROL: MONITOR OBJECTS: MONITOR BALANCES: Option = Full END MONITOR FORCES: Option = Full END MONITOR PARTICLES: Option = Full END MONITOR POINT: Angular_Velocity Expression Value = rbstate(Angular Velocity)@Rotor Option = Expression END MONITOR POINT: Circumferential Velocity Expression Value = ave(Velocity)@REGION:R 1 Side 2 Option = Expression END MONITOR POINT: Circumferential Velocity 2 Expression Value = ave(Velocity)@REGION:R 2 Side 2 Option = Expression END MONITOR POINT: Torque on Rotor Expression Value = torque_y()@RotorBody Option = Expression END MONITOR RESIDUALS: Option = Full END MONITOR TOTALS: Option = Full END END RESULTS: File Compression Level = Default Option = Standard END TRANSIENT RESULTS: Transient Results 1 File Compression Level = Default Include Mesh = No Option = Selected Variables Output Variables List = Pressure,Total Mesh Displacement,Mesh \ Displacement,Velocity,Mesh Velocity OUTPUT FREQUENCY: Option = Time Interval Time Interval = 0.1 [s] END END END RIGID BODY: Rotor Location = R Stand,R Endplate Top,R Endplate Peripheri,R Endplate \ Bottom,R 2 Top,R 2 Side 2,R 2 Side 1,R 2 Outer,R 2 Inner,R 1 Top,R 1 \ Side 2,R 1 Side 1,R 1 Outer,R 1 Inner Mass = 3.2848 [kg] Rigid Body Coord Frame = Coord 1 DYNAMICS: DEGREES OF FREEDOM: ROTATIONAL DEGREES OF FREEDOM: Option = Y axis END TRANSLATIONAL DEGREES OF FREEDOM: Option = None END END GRAVITY: Gravity X Component = 0 [m s^2] Gravity Y Component = g Gravity Z Component = 0 [m s^2] Option = Cartesian Components END END INITIAL CONDITIONS: ANGULAR VELOCITY: Option = Automatic with Value xValue = 0 [radian s^1] yValue = 0 [radian s^1] zValue = 0 [radian s^1] END CENTRE OF MASS: Option = Automatic END LINEAR VELOCITY: Option = Automatic with Value xValue = 0 [m s^1] yValue = 0 [m s^1] zValue = 0 [m s^1] END END MASS MOMENT OF INERTIA: xxValue = 0 [kg m^2] xyValue = 0 [kg m^2] xzValue = 0 [kg m^2] yyValue = 0.2390 [kg m^2] yzValue = 0 [kg m^2] zzValue = 0 [kg m^2] END END SOLVER CONTROL: Turbulence Numerics = First Order ADVECTION SCHEME: Option = High Resolution END CONVERGENCE CONTROL: Maximum Number of Coefficient Loops = 5 Minimum Number of Coefficient Loops = 1 Timescale Control = Coefficient Loops END CONVERGENCE CRITERIA: Residual Target = 1.E4 Residual Type = RMS END RIGID BODY CONTROL: RIGID BODY SOLVER COUPLING CONTROL: Update Frequency = Every Coefficient Loop END END TRANSIENT SCHEME: Option = Second Order Backward Euler TIMESTEP INITIALISATION: Option = Automatic END END END END COMMAND FILE: Version = 13.0 Results Version = 13.0 END SIMULATION CONTROL: EXECUTION CONTROL: EXECUTABLE SELECTION: Double Precision = On END INTERPOLATOR STEP CONTROL: Runtime Priority = Standard MEMORY CONTROL: Memory Allocation Factor = 1.0 END END PARALLEL HOST LIBRARY: HOST DEFINITION: aa1001304 Remote Host Name = AA1001304 Host Architecture String = winntamd64 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 = kway Option = MeTiS Partition Size Rule = Automatic END END RUN DEFINITION: Run Mode = Full Solver Input File = C:\Users\U1031944\Desktop\Conventional Savonius \ Turbine\auto_files\dp0\CFX1\CFX\CFX_test.def END SOLVER STEP CONTROL: Runtime Priority = Standard MEMORY CONTROL: Memory Allocation Factor = 1.0 END PARALLEL ENVIRONMENT: Number of Processes = 1 Start Method = Serial END END END END 

May 17, 2012, 06:10 

#2 
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Glenn Horrocks
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It is likely the device is accelerating and will take a while to reach equilibrium. Rather than using the rigid body solver I recommend you do a series of steady state (well, frozen rotor actually) simulations at different rotation speeds. A series of frozen rotor simulations are far easier to do than a single rigid body model.
This gives you a map of torque produced against rotational speed. At the point the torque equals the load (ie zero net torque) that is the steady state operating point of the device. 

May 17, 2012, 21:48 

#3 
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Abdullah Al Faruk
Join Date: Apr 2012
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Thank you very much Glenn.


May 2, 2013, 17:39 

#4 
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asmita
Join Date: Apr 2013
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Hello I want to find out the angular velocity and torque of a turbine in FluentAnsys. Is it possible to find out ? My turbine rotates in one direction and its enclosed in a rectangle . THe geometry in drawn using Gambit software


May 2, 2013, 18:40 

#5 
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Glenn Horrocks
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Try the fluent forum.


May 28, 2013, 08:01 

#6  
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Quote:
i had simulated a wind turbine using fluent and now i want to calculate the output power using torque.(reportmoment) but all the amounts which i had calculated using this method is 10 times bigger than real amounts i don't now what to do. would you plz help me??? 

May 28, 2013, 21:36 

#7 
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Glenn Horrocks
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FAQ: http://www.cfdonline.com/Wiki/Ansys..._inaccurate.3F
And you will get more specific help on Fluent on the Fluent forum. 

December 3, 2013, 16:31 
help me

#8 
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khaled
Join Date: Sep 2013
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I want how to make to simulate Savonius wind turbine using the rigid body solver of ANSYS CFD v12.1 with sliding mesh of subdomain. How can I calculate angular velocity of rotor and torque on rotor in CFD or CFXpost? and how to calcute drag coefficient and lift coefficient


December 3, 2013, 16:51 

#9 
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Glenn Horrocks
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Using the rigid body solver for this is not recommended. I explain why in post #2. Use a series of frozen rotor simulations at various speeds instead.


March 16, 2017, 06:35 

#10  
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mahdi
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Quote:
thanks 

March 16, 2017, 17:38 

#11 
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Glenn Horrocks
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The load torque is what it is driving. So the generator or whatever is connected to it.


March 17, 2017, 03:36 

#12  
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mahdi
Join Date: Nov 2015
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Quote:
please give me a suggestion. thank you very much 

March 17, 2017, 04:10 

#13 
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Glenn Horrocks
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The generator will have a performance curve, that is torque versus speed. Likewise the turbine will have a torque versus speed curve. Where these curves intersect (ie they are equal) is the steady state operating point of the system.
Design of these systems so the generator is appropriately sized to the turbine is not a trivial issue and may require you to run a range of options to see what runs best. 

March 17, 2017, 05:05 

#14  
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mahdi
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Quote:
Generator is not matter because I have to calculation angular velocity that occur by inlet velocity. If I suppose system doesn't have generator and turbine is free, how can I calculate the angular velocity? 

March 17, 2017, 06:08 

#15 
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Glenn Horrocks
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If the turbine is free spinning with nothing connected to it then simply find the speed at which it generates zero torque. That will be the steady state, free spinning speed.


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cfx 13, wind turbines 
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