Initial conditions

In this section you can define the initial conditions of the model, i.e. the conditions at t = 0. Note that if the option Loads only is selected in the Analysis parameters, these conditions will remain unchanged during the simulation.

The Initial conditions can be accessed by opening the Analysis parameters dialog and selecting the Initial conditions tab.

General

RPM, TSR, or Tip speed

Select if the RPM, TSR, or Tip speed should be the initial condition.

Based on this parameter, only the relevant initial condition is visible (RPM, TSR, or Tip speed).


If the main shaft is locked (the parameter Main shaft -> Advanced ->Bearings locked is checked), then this parameter is set to Specify RPM and disabled (but still visible).

Options:

Specify RPM (default):

Initial condition is set by RPM.

Specify TSR:

Initial condition is set by TSR.

Specify Tip speed:

Initial condition is set by tip speed.

RPM

Initial revolutions per minute of the rotor.

This is only visible if the RPM, TSR, or Tip speed parameter is set to Specify RPM.


This is also used as the initial RPM of the main shaft. The initial RPM of the generator is set by also using the gearbox ratio. If there is no gearbox, then the initial RPM of the gearbox is the same as the initial RPM of the rotor.


If the main shaft is locked (parameter Main shaft -> Advanced ->Bearings locked is checked), then the initial RPM is set to 0 and the parameter disabled (but still visible).

  • Default value: 10
  • Unit: $\text{rpm}$
  • Range: -10000 — 10000

TSR

The initial tip-speed ratio (tip speed divided by wind speed)

  • Default value: 7
  • Unit: —
  • Range: 0 — 1e+06

Tip speed

The tip speed of the rotor

  • Default value: 80
  • Unit: ${\text{m}} \over {\text{s}}$
  • Range: 0 — 1e+06

Pitch angle

Note: This option is currently disabled, and the initial pitch angle will be always be 0. If you want to simulate a pitched blade, set the Demanded pitch scheme to PID controller on the RNA, and set the minimum and maximum pitch angle to the wanted angle on the Demanded pitch part. This way, the blade will pitch to the requested angle when the simulation starts. We expect a fix for the next release.

The pitch angle of the blade with respect to the pitch axis. Positive values means pitch-to-feater (the leading edge is twisted against the wind). Negative values means pitch-to-stall.

  • Default value: 0
  • Unit: $°$
  • Range: -180 — 180

Azimuth angle scheme

Specifies the scheme for setting the initial azimuth angle of the rotor(s)


Options:

Same for all (default):

The azimuth angle is set to the same value for all rotors.

Randomized:

The azimuth angle is randomized, so that each rotor gets a different value.

Azimuth angle

The initial rotation of the rotor, where a positive angle is in the clockwise direction (as seen from the front).


  • Default value: 0
  • Unit: $°$
  • Range: -360 — 360

Yaw angle

The initial yaw angle of the RNA.


  • Default value: 0
  • Unit: $°$
  • Range: -360 — 360

Use modeshape as initial condition

Use a modeshape as the initial condition of the simulation.


  • Default value: False
  • Unit: —

Modeshape file

The file that contains the eigenmodes/modeshapes to use as initial condition. To use an eigenmode as initial condition, first go to Eigenmodes tool and generate the eigenmodes table, export the results to a file, and then select this file here.


  • Default value:
  • Unit: —

Mode number

The number of the mode to use as initial condition. For example, a value of 1 will use the first mode in the modeshape file.


  • Default value: 1
  • Unit: —
  • Range: 1 — 1e+06

Floaters

Find initial static equilbrium position

A static analysis can be performed before the time simulation, to avoid long transients. During the static phase, all loads are applied as if time equals zero, and dynamic loads are ignored (such as wave loads and turbulence). The platform is then moved to this position before the time simulation starts.




  • Default value: False
  • Unit: —