52. ABA turbine feature

The identification tag for this tutorial is PDS-ABM. Pregenerated input files for this tutorial are found in the folder named PDS-ABM in the provided tutorial input files.

52.1. Tutorial overview

This tutorial covers:

  • Turbine features with a RigidBody rotor
  • Specifying prescribed tip speed ratios
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Fig. 52.1 Simple turbine model

52.2. Creating the base RigidBody

  • Create a new project.
  • Create a RigidBody DObject and call it platform.
  • Set $Kinematic 1.
  • Define the initial state z position to -50 m (in the air).

Note

  • This will represent the stationary portion of the turbine.
  • Give the base a cuboid feature coincident with the RigidBody frame for a visual reference.

52.3. Creating the rotating RigidBody

  • Create a RigidBody DObject and call it rotor.
  • Set the mass and the moments of inertia to 1e5.

Note

  • This will represent the rotating portion of the turbine.
  • Create a cuboid feature called blade as a visual representation of the rotor.
  • The thrust and torque will be produced by the turbine feature: set the blade feature $WindLoading 0, $HydroLoading 0, $BuoyancyFroudeKrylov 0 and $SoilLoading 0.

Note

  • The turbine feature will also adjust the rotation speed of the rotor.
  • Set $Kinematic 1.
  • Make blade 0.25 m along the x axis, 30 m along the y axis, and 0.75 m along the z axis.
  • Add the cuboid feature to the rotor using $Cuboid blade 0 0 0 0 0 0.

Note

  • The blade library feature should look like the following:
// Added Mass Coefficients
$CAx 0
$CAy 0
$CAz 0

// Dimensions
$LengthX 0.25
$LengthY 30
$LengthZ 0.75

// Drag Coefficients
$CDt 0
$CDx 0
$CDy 0
$CDz 0

// Fluid loading
$WindLoading 0
$HydroLoading 1
$HydrostaticFroudeKrylov 1

// Mesh
$SegmentsX 5
$SegmentsY 5
$SegmentsZ 5

// Soil loading
$SoilLoading 1

52.4. Connecting the rigid bodies via ABA connection

Note

  • The platform and rotor will be connected by a revolute ABA joint.
  • Make an ABA connection with the platform as the master and the rotor as master.
  • Define the connection under the Connections heading to be revolute about the x axis.
// Mechanical
$MasterConnectionLocation 0 0 0 0 0 0
$FollowerConnectionLocation 0 0 0 0 0 0
$Joint 1
$RevoluteJointAngular jointProperties
$FollowerJointAxis 0

Note

  • A default joint properties feature called jointProperties is automatically created when an ABA connection is made.
  • Set the state of rotor to ABA with an initial displacement and displacement rate of 0.

52.5. Creating a turbine feature

  • Create a RigidBody turbine feature by selecting RigidBody Turbine in the Add Feature drop down menu.
  • Call the new turbine feature turbine_30m.

Note

  • Within the turbine feature library item the torque and thrust coefficient tables must be created.
  • The torque and thrust coefficients can be set to be dependent on either tip speed ratio (TSR), relative fluid velocity, or both.
  • For this example, the thrust and torque coefficients are dependent only on TSR, and independent of relative fluid velocity. This is typical of a rigid bladed turbine that does not have blades that flex or pitch to reduce loading and power. This is achieved by leaving the coefficient tables defined as a single column set of coefficients. The coefficient columns are defined using $RelativeFluidVelocities 0 which in this case is left as default.
  • The prescribed TSR for the turbine is set using the $PrescribedTSR property. This sets the control scheme for the turbine. The turbine will react to changes in the relative fluid velocity to achieve the prescribed TSR.
  • The turbine feature can update its parent RigidBody velocity based on prescribed tip speed ratio of operation.
  • Set $ControlParentRB 1.
  • Update the turbine properties as listed below:
// Configuration
$Mode 0
$ReferenceSweptArea 700
$ReferenceDiameter 30
$IsCrossFlowTurbine 0
$RotationAxis 0
$CutInSpeed 0
$CutOutSpeed 100
$ControlParentRB 1

// Scheduling
$ScheduleMode 0

// Thrust and Torque Data
$RelativeFluidVelocities 0
$TorqueCoefficient 0 0.1
$TorqueCoefficient 4.5 1
$TorqueCoefficient 8 0

$ThrustCoefficient 0 0
$ThrustCoefficient 4.5 0.5
$ThrustCoefficient 8 0.5

$PrescribedTSR 0 0
$PrescribedTSR 2 4.5
$PrescribedTSR 4 8

// Transient Response Model
$TransientResponseModel 0
  • Add the turbine feature to the rotor RigidBody.

Note

  • The input file to the rotor should look like the listing below:
// Mass properties
$Ix 1e5
$Iy 1e5
$Iz 1e5
$Ixy 0
$Ixz 0
$Iyz 0
$DefineInertiaAboutCG 0
$CGPosition 0 0 0
$Mass 1e5

// Numerical
$Kinematic 1

$Cuboid blade 0 0 0 0 0 0
$Turbine turbine_30m 0 0 0 0 0 0

52.6. Simulate the turbine in constant wind

  • In the environment input, set a constant uniform wind with speed of 10 m/s as indicated below:
$WindProfile 0
$WindHeading 0
$WindSpectrum 0
$WindSpeed 10
  • Run the simulation for 10 seconds.

Note

  • The prescribed tip speed ratio corresponding to 10 m/s is 4.5 and as an axial flow turbine, the expected thrust and torque values are 23 kN and in the x-direction and 677 kNm about the x axis, respectively.
  • Confirm loading on the platform in the turbineOutput.dat and forces.dat file in the turbine feature results folder.

Note

  • Note the turbine rotor is now visualized by the spinning rotor.
  • Run a simulation for 10 seconds and visualize the rotor spinning.
  • Open the forces output file and compare the values to expected results.