54. Turbine platform

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

54.1. Tutorial overview

This tutorial covers:

  • Creating a turbine feature
  • Revolute ABA connection
  • Creating a moored turbine platform
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Fig. 54.1 Simple turbine platform model

54.2. Creating the platform RigidBody

  • Create a new project.
  • Create a RigidBody DObject and call it platform.
  • Set the mass and the moments of inertia to 1e4.
  • To help with roll and pitch stability, set $CGPosition 0 0 1 and also $DefineInertiaAboutCG 1.
  • Define the initial state z position to 20 and the initial x position to 100.

Note

  • The turbine platform will consist of 3 features; 2 side cylinders and a center cuboid.
  • Create a cuboid feature called frame.
  • Set the length dimensions using $LengthX 3, $LengthY 12, and $LengthZ 0.2.

Note

  • The remaining cuboid feature properties can be left as default.
  • Create a cylinder feature called stator.
  • Set the length and diameter dimensions using $Length 6 and $Diameter 1.5.

Note

  • The remaining cylinder feature properties can be left as default.
  • Add the frame feature to the RigidBody coincident to the local RigidBody frame.
  • Add 2 stator features to the RigidBody ±6 m along the Y axis and rotate each stator 90 degrees about the Y axis.

54.3. Creating the rotors

  • Create 2 RigidBody DObjects and call then rotor0 and rotor1.
  • Set the mass and the moments of inertia to 1e3 and 1e2, respectively.
  • Create a cuboid feature called blade as a visual representation of the rotor.
  • Disable all loading properties in the cuboid feature as the thrust and torque will be produced by the turbine feature.
  • Set $WindLoading 0, $BuoyancyFroudeKrylov 0, $HyrdoLoading 0, and $SoilLoading 0.
  • Make the blade 0.1 m along the x axis, 5 m along the y axis, and 0.5 m along the z axis.
  • Add the cuboid feature to each rotor using $Cuboid blade 0 0 0 0 0 0.
// Added Mass Coefficients
$CAx 1
$CAy 1
$CAz 1

// Dimensions
$LengthX 0.1
$LengthY 5
$LengthZ 0.5

// Drag Coefficients
$CDt 0.1
$CDx 1
$CDy 1
$CDz 1

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

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

// Soil loading
$SoilLoading 1

54.4. 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 tab to be revolute about the x axis.
  • Place the platform connection location at (3,6,0) m with respect to the platform frame, as shown below.
// Mechanical
$MasterConnectionLocation 3 6 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 rotor0 to ABA with an initial displacement and displacement rate of 0.
  • Repeat the above process for rotor1 but place the connection at (3,-6,0) m with respect to the platform frame.

54.5. Connecting the rigid bodies via ABA connection

  • Create a RigidBody turbine feature by selecting RigidBody Turbine in the Add New Library Feature drop down menu.
  • Reference the new turbine feature turbine_2m.

Note

  • Within the turbine feature library item, the torque and thrust coefficient tables must be created.
  • These tables define torque and thrust to be applied to the turbine rotor for a given tip speed ratio (TSR). For TSR between data points, linear interpolation is employed.
  • Update the turbine properties as listed below.
// Configuration
$Mode 0
$ReferenceSweptArea 3
$ReferenceDiameter 2
$IsCrossFlowTurbine 0
$RotationAxis 0
$CutInSpeed 0
$CutOutSpeed 100

// Scheduling
$ScheduleMode 0

// Thrust and Torque Data
$RelativeFluidVelocities 0
$TorqueCoefficient 0 0.1
$TorqueCoefficient 1 0.5
$TorqueCoefficient 2 1
$TorqueCoefficient 3 1.5
$TorqueCoefficient 6 0

$ThrustCoefficient 0 0.1
$ThrustCoefficient 1 0.5
$ThrustCoefficient 2 1
$ThrustCoefficient 3 1.5
$ThrustCoefficient 4 1.5

$PrescribedTSR 0 0
$PrescribedTSR 2 4
$PrescribedTSR 4 6

// Transient Response Model
$TransientResponseModel 0
  • Add the turbine feature to the rotor0 RigidBody.
  • Add the turbine feature to the rotor1 RigidBody.

Note

  • The input file to either rotor0 or rotor1 should look like the listing below.
// Mass properties
$Ix 1e2
$Iy 1e2
$Iz 1e2
$Ixy 0
$Ixz 0
$Iyz 0
$DefineInertiaAboutCG 0
$CGPosition 0 0 0
$Mass 1e3

// Numerical
$Kinematic 0

$Turbine turbine_2m 0 0 0 0 0 0
$Cuboid blade 0 0 0 0 0 0

54.6. Create the mooring and bridles

  • Add a new cable called mooring.
  • Place node 0 at (100,0,50) m and node N at (0,0,500) m. Give the cable a length of 460 m with 10 elements.
  • Set node N static to simulate an ideal anchor.

Note

  • Node 0 of mooring will connect to 2 bridles which will be attached to either end of the platform.
  • Add 2 cables to the project called bridle0 and bridle1.
  • For bridle0, place node 0 at (100,6,20) m and node N at (100,0,50) m. Give the cable a length of 30 with 3 elements.
  • For bridle1, place node 0 at (100,-6,20) m and node N at (100,0,50) m. Give the cable a length of 30 with 3 elements.
  • In the library, create a DCableSegment feature called rope with the following properties:
// Axial Rigidity
$AxialRigidityMode 0
$EA 4.3e6

// Fluid loading
$CDc 1
$CDt 0.1
$CAc 1

// Mechanical
$EI1 1
$EI2 1
$GJ 0
$Diameter 0.052
$Density 980
$AxialDampingMode 1
$AxialReferenceDampingRatio 0.5
$BCID 0
$TCID 0
$CE 1

// Strain Limit
$ElongationLimitMode 0
  • Add the rope cable segment to mooring, bridle0, and bridle1.
  • Use the other default values in the cable properties file.
  • Connect each bridle node N to node 0 of mooring.
  • Connect bridle0 node 0 using a point connection to platform at (-0.5,6,0.75) m.
  • Connect bridle1 node 0 using a point connection to platform at (-0.5,-6,0.75) m.

54.7. Simulate the platform in constant current

  • In the environment input, set a water depth of 500 m and a constant uniform current with speed of 2 m/s.
  • Run the simulation for 20 seconds.

Note

  • The turbine feature uses the relative fluid velocity to determine the prescribed TSR and the resulting angular velocity.
  • Confirm loading on the platform in the forces.dat file in the Results folder.

Note

  • Note ABA joint visualizes the rotation speed of the rotors.