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-   -   Difficulty in calculating angular velocity of Savonius turbine simulation (http://www.cfd-online.com/Forums/cfx/101911-difficulty-calculating-angular-velocity-savonius-turbine-simulation.html)

 alfaruk May 17, 2012 00:02

Difficulty in calculating angular velocity of Savonius turbine simulation

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 CFX-post? While calculating the angular velocity in CFX-Solver Manager using the rigid body state function (rbstate(Angular Velocity Y)@Rotor), the angular velocity is continuously increasing.

Attached is the CCL for run.

With Thanks
Abdullah

LIBRARY:
CEL:
EXPRESSIONS:
Air Density = 1.185 [kg m-3]
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 s-1]
END
END
Option = Definition
Tensor Type = SCALAR
Variable Type = Specific
END
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 = 1.831E-05 [kg m^-1 s^-1]
Option = Value
END
THERMAL CONDUCTIVITY:
Option = Value
Thermal Conductivity = 2.61E-02 [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:
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
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
Option = None
END
TURBULENCE MODEL:
Option = k epsilon
END
TURBULENT WALL FUNCTIONS:
Option = Scalable
END
END
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
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
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.E-4
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 = AA10-01304
Host Architecture String = winnt-amd64
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:
Run Mode = Full
Solver Input File = C:\Users\U1031944\Desktop\Conventional Savonius \
Turbine\auto_files\dp0\CFX-1\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

 ghorrocks May 17, 2012 06:10

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.

 alfaruk May 17, 2012 21:48

Thank you very much Glenn.

 asmita May 2, 2013 17:39

Hello I want to find out the angular velocity and torque of a turbine in Fluent-Ansys. 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

 ghorrocks May 2, 2013 18:40

Try the fluent forum.

 niloogh May 28, 2013 08:01

Quote:
 Originally Posted by ghorrocks (Post 361623) 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.
hi ghorrock
i had simulated a wind turbine using fluent and now i want to calculate the output power using torque.(report-moment)
but all the amounts which i had calculated using this method is 10 times bigger than real amounts:confused:
i don't now what to do.
would you plz help me???

 ghorrocks May 28, 2013 21:36

FAQ: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

And you will get more specific help on Fluent on the Fluent forum.

 khaled ali December 3, 2013 17:31

help me

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 CFX-post? and how to calcute drag coefficient and lift coefficient

 ghorrocks December 3, 2013 17:51

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.

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