35. Wind models

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

35.1. Tutorial overview

This tutorial covers:

  • Creating a RigidBody DObject
  • Setting RigidBody state
  • Creating a RigidBody Cylinder feature

35.2. Creating a RigidBody DObject

  • Initialize a vertical RigidBody using a RigidBodyCylinder feature. Give the RigidBody 0 initial displacement and rotation about the global reference frame.
  • Set the cylinder feature coordinate frame to be coincident with the RigidBody frame.
  • Use the following properties in the RigidBody DObject input file:
// Mass properties
$Ix 134
$Iy 134
$Iz 1
$Ixy 0
$Ixz 0
$Iyz 0
$DefineInertiaAboutCG 1
$CGPosition 0 0 2
$Mass 100

// Numerical
$Kinematic 0

$Cylinder rigidBodyCylinder 0 0 0 0 0 0

Note

  • The center of gravity was moved relative to the RigidBody frame by 2 m in the z direction. This places the center of gravity below the center of buoyancy, therefore making the cylinder more stable as it floats in the water.
  • Add the flag $DefineInertiaAboutCG 1. This indicates that the mass moment of inertia values specified are about a corresponding frame located at the CG location. This will result in an automatic parallel axis computation to determine the total equivalent inertia seen at the RigidBody local frame.
  • Use the following properties for the RigidBodyCylinder:
// Added Mass Coefficients
$CaAxial 1
$CaNormal 1

// Dimensions
$Diameter 0.25
$Length 4

// Drag Coefficients
$CDt 1
$CdAxial 1
$CdNormal 1

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

// Mesh
$AxialSegments 10
$RadialSegments 2
$AngularSegments 8

// Soil loading
$SoilLoading 1

Note

  • Note the optional property $CDt set to 1. This enables the fluid tangential drag.
  • Set the simulation end time to 30 seconds and run the simulation.
  • View the results in PostPDS. Notice the cylinder bobbing in the water with zero horizontal displacement. This is due to the absence of current, waves, or wind acting on the RigidBody.

35.3. Applying wind to the simulation

Note

  • To enable wind in the simulation, several properties associated with wind must be declared.
  • A time varying wind is produced by selecting a specific spectrum.
  • Variation in the wind speed with height is produced by selecting a specific profile.
  • More information on the available wind spectra and profiles can be found in the ProteusDS User Manual.
  • To enable a uniform profile with an Ochi-Shin spectrum, add the following properties to the environment input file: $WindProfile 1, $WindSpectrum 1.
  • Due to the fact that the Ochi-Shin spectrum was chosen, several follower properties must be declared. Use the following properties to create the Ochi-Shin spectrum:
$WindProfile 1
$WindSurfaceRoughness 0.01
$WindHeading 0
$WindSpectrum 1

$WindCutOffFreq 100
$WindNumFreq 50
$Wind10MinMeanSpeed 5

Note

  • More information on the specific wind properties and their masters can be found in the ProteusDS User Manual Input Files Appendix.

35.4. Running the simulation and visualizing in PostPDS

  • Run the simulation again and view in PostPDS.

Note

  • Notice the cylinder being displaced horizontally due to the wind loading.
  • The wind only acts on the portion of the RigidBody above the water and if the RigidBody feature has the $WindLoading property enabled.