Static analysis

A static analysis finds the equilibrium position and deformation of the wind turbine structure when exposed to external loads. 

You can run a static analysis by changing Analysis type to Static in the Analysis parameters window. 

1 Loads 

  • The static analysis can be either nonlinear (which is default), and linear. (Ref. nonlin vs linear analyses.) During a static analysis, dynamic loads and effects will be ignored. 
  • The wind field is assumed to be constant, with the wind type and speed that is currently set. Turbulence is ignored. 
  • The wind loads are computed for a rotor rpm that is constant, set to the initial rpm. 
  • The steady BEM method is used. The rotor azimuth angle remains fixed at the initial angle. 
  • Tower shadow effects are ignored. 
  • The pitch angle remains constant, with the initial pitch angle. (ref. Initial conditions). You must manually set the pitch angle to the value that the wind turbine will operate at for the given rpm, in order to get a correct wind load situation. 
  • All loads due to structural velocities and accelerations are zero. Displacements are not zero, and will reach the equilibrium position when the analysis completes. 
In addition, for an offshore model: 
  • Waves are ignored, i.e. all wave components will have zero amplitude. The sea surface level will stay constant at the mean sea level, or at the tidal level if tides are modeled. (Ref. wave/amplitude/tides). 
  • Since structural velocities and accelerations are by definition zero, drag and inertia loads due to movement are zero. 
  • Drag loads due to e.g. currents are included. 
  • Mooring lines must be modeled either with linear springs, or with nonlinear springs. (ref. nonlin spring/spring stiffness Table). 
  • In general, all other loads--such as an imported load history--will be applied with their value at time t = 0. 

2 Sensor results 

Sensors will record data also for a static analysis, similar to when running a dynamic time simulation. There are some differences, namely: 
  • The entries in the time column of each sensor starts at a negative time and steps up to zero when reaching the final static equilibrium position. 
  • Although there is strictly no time in a static analysis, the time column will show a time that depends on the timestep currently set. For example, if the timestep is 0.025 s and loads are applied in 10 increments, the time will run from -0.25 to 0 in 0.025 second increments.