[mshahed91]

Hello Everyone,

I am very new to CFD and I have carried out a simulation for a undershot waterwheel placed inside a pipeline. Currently I have used a rigid body for my waterwheel, and have two domains, one for the region surrounding the rigid body and another for the remainder of the pipe. I have specified my rotor domain as a subdomain with the option of rigid body solution and have also used a wall boundary condition for the wheel walls with the option of rigid body solution.

To calculate power, I use different external torques (on the opposite direction to rotation) on the rigid body and see what my final angular velocity and try to find the optimum torque for which I have max power (Torque times angular velocity). I have attached several images to help explain what I have done. I would greatly appreciate any suggestions to help improve the accuracy of my simulation since I am not sure I am doing it right.

Best Regards,
Mohaimin

LIBRARY:
COORDINATE FRAME DEFINITIONS:PlotData.png

BackView.JPG

IsoView.JPG

Setupview.jpg

WireframeView.JPG
COORDINATE FRAME: Coord 1
Axis 3 Point = 0.0[m],0.0[m],1.0[m]
Coord Frame Type = Cartesian
Option = Axis Points
Origin Point = 0.0[m],0.0[m],0.0[m]
Plane 13 Point = 1.0[m],0.0[m],0.0[m]
Reference Coord Frame = Coord 0
END
END
MATERIAL: Crude Oil
Material Group = User
Option = Pure Substance
PROPERTIES:
Option = General Material
EQUATION OF STATE:
Density = 870 [kg m^-3]
Molar Mass = 154 [kg kmol^-1]
Option = Value
END
DYNAMIC VISCOSITY:
Dynamic Viscosity = 0.0105 [Pa s]
Option = Value
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 = 3 [s]
END
TIME STEPS:
Option = Timesteps
Timesteps = 0.025 [s]
END
END
DOMAIN: Rotor
Coord Frame = Coord 1
Domain Type = Fluid
Location = B763
BOUNDARY: Default Fluid Fluid Interface Side 1
Boundary Type = INTERFACE
Location = F583.763
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
MESH MOTION:
Option = Stationary
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: Domain Interface 1 Side 1
Boundary Type = INTERFACE
Location = RotorInterface1
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
MESH MOTION:
Option = Stationary
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: RotorWall
Boundary Type = WALL
Location = RotorWall
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
Wall Velocity Relative To = Mesh Motion
END
MESH MOTION:
Option = Rigid Body Solution
Rigid Body = Rigid Body 1
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
END
BOUNDARY: Symmetry
Boundary Type = SYMMETRY
Location = F586.763
BOUNDARY CONDITIONS:
MESH MOTION:
Option = Unspecified
END
END
END
DOMAIN MODELS:
BUOYANCY MODEL:
Option = Non Buoyant
END
DOMAIN MOTION:
Option = Stationary
END
MESH DEFORMATION:
Displacement Relative To = Previous Mesh
Option = Regions of Motion Specified
MESH MOTION MODEL:
Option = Displacement Diffusion
MESH STIFFNESS:
Option = Increase near Small Volumes
Stiffness Model Exponent = 2.0
REFERENCE VOLUME:
Option = Mean Control Volume
END
END
END
END
REFERENCE PRESSURE:
Reference Pressure = 1 [atm]
END
END
FLUID DEFINITION: Fluid 1
Material = Crude Oil
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
HEAT TRANSFER MODEL:
Option = None
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Option = k epsilon
END
TURBULENT WALL FUNCTIONS:
Option = Scalable
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
SUBDOMAIN: Subdomain 1
Coord Frame = Coord 1
Location = B763
MESH MOTION:
Option = Rigid Body Solution
Rigid Body = Rigid Body 1
END
END
END
DOMAIN: Stator
Coord Frame = Coord 1
Domain Type = Fluid
Location = B640
BOUNDARY: Default Fluid Fluid Interface Side 2
Boundary Type = INTERFACE
Location = F493.640
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: Domain Interface 1 Side 2
Boundary Type = INTERFACE
Location = StatorInterface1
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = Conservative Interface Flux
END
TURBULENCE:
Option = Conservative Interface Flux
END
END
END
BOUNDARY: Inlet
Boundary Type = INLET
Location = F486.640
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Normal to Boundary Condition
END
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Mass Flow Rate = 1100 [kg s^-1]
Option = Mass Flow Rate
END
TURBULENCE:
Option = Medium Intensity and Eddy Viscosity Ratio
END
END
END
BOUNDARY: Outlet
Boundary Type = OUTLET
Location = F485.640
BOUNDARY CONDITIONS:
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Mass Flow Rate = 1100 [kg s^-1]
Option = Mass Flow Rate
END
END
END
BOUNDARY: Symmetry2
Boundary Type = SYMMETRY
Location = F491.640
END
BOUNDARY: Wall
Boundary Type = WALL
Location = Wall
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
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: Fluid 1
Material = Crude Oil
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
HEAT TRANSFER MODEL:
Option = None
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Option = k epsilon
END
TURBULENT WALL FUNCTIONS:
Option = Scalable
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
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
DOMAIN INTERFACE: Domain Interface 1
Boundary List1 = Domain Interface 1 Side 1
Boundary List2 = Domain Interface 1 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
OUTPUT CONTROL:
MONITOR OBJECTS:
MONITOR BALANCES:
Option = Full
END
MONITOR FORCES:
Option = Full
END
MONITOR PARTICLES:
Option = Full
END
MONITOR POINT: Monitor Point 1
Coord Frame = Coord 1
Expression Value = torque_z@RotorWall
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
Option = Standard
OUTPUT FREQUENCY:
Option = Time Interval
Time Interval = 0.075 [s]
END
END
END
RIGID BODY: Rigid Body 1
Location = RotorWall
Mass = 5.15 [kg]
Rigid Body Coord Frame = Coord 1
DYNAMICS:
DEGREES OF FREEDOM:
ROTATIONAL DEGREES OF FREEDOM:
Option = Z axis
END
TRANSLATIONAL DEGREES OF FREEDOM:
Option = None
END
END
GRAVITY:
Gravity X Component = 0 [m s^-2]
Gravity Y Component = -9.81 [m s^-2]
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 = 0.048 [kg m^2]
xyValue = 0 [kg m^2]
xzValue = 0 [kg m^2]
yyValue = 0.048 [kg m^2]
yzValue = 0 [kg m^2]
zzValue = 0.051 [kg m^2]
END
END
SOLVER CONTROL:
Turbulence Numerics = First Order
ADVECTION SCHEME:
Option = High Resolution
END
CONVERGENCE CONTROL:
Maximum Number of Coefficient Loops = 10
Minimum Number of Coefficient Loops = 1
Timescale Control = Coefficient Loops
END
CONVERGENCE CRITERIA:
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 = 15.0
Results Version = 15.0
END
SIMULATION CONTROL:
EXECUTION CONTROL:
EXECUTABLE SELECTION:
Double Precision = Off
END
INTERPOLATOR STEP CONTROL:
Runtime Priority = Standard
DOMAIN SEARCH CONTROL:
Bounding Box Tolerance = 0.01
END
INTERPOLATION MODEL CONTROL:
Enforce Strict Name Mapping for Phases = Off
Mesh Deformation Option = Automatic
Particle Relocalisation Tolerance = 0.01
END
MEMORY CONTROL:
Memory Allocation Factor = 1.0
END
END
PARALLEL HOST LIBRARY:
HOST DEFINITION: winserv5
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 = No gap from turbine to wall but same dim.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]

Have you read the FAQ on accuracy? http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

[mshahed91]

Hello Ghorrocks,

Thanks for your reply. I had done some sensitivity analysis with regards to grid density, turbulence model and turbulence intensity. But so far I have used smooth walls for my rigid body. For some reason inflating the region around my rigid body has not changed my results much, so I am wondering if I am doing something wrong.

[tomson199]

Hi mshahed91

I have a problem, cause I try to simulate simply wind turbine to find angular velocity of rotor, but unfortunately it still fail. I created domain, subdomain, and rigid body to pattern from your CEL library.Probably the problem is cennected with mesh motion and setup with that. The question is: Could you send to me your file with this simulation of waterwheel? Also I can send to you my file with my wind turbine.

Regards,
Tomasz