Dynamic Simulations

Dynamic or time-domain simulations are used to calculate the loads, deflections and control response of the wind turbine as a function of time. Bladed incorporates models to capture the environmental conditions, the structural model and the control response to simulate the fully-coupled response of the turbine. The user can simulate onshore, offshore fixed and floating wind turbine models.

Time-domain simulations may be used, for example, to simulate the behaviour of a turbine for period of, say, 10 minutes at each of a number of wind speeds. The resulting loads can be analysed to produce a representative fatigue load spectrum for the turbine or the extreme loads on the structure.

The following simulations may be run:

• Power production (normal operation)

• Normal stop

• Emergency stop

• Startup

• Idling

• Parked

• Hardware test (for users with a Hardware Test Module licence)

The full dynamics of the turbine will be used for all these simulations, together with the appropriate supervisory control parameters which define the stopping and starting logic, and the state of the machine when idling or parked.

The user should select an appropriate [integrator] to run a time-domain simulation.

Simulation control

Use the Simulation control screen to define various parameters which control the progress of a simulation. These parameters are defined below:

• Output time step: This is the time interval at which the output variables are sampled and saved to output files. It must be a non-zero positive number. If using a fixed step integrator, this must be an integer multiple of the integrator step size

• Time to start writing output: Some simulations may start with a small transient, if the initial conditions are not calculated to sufficient accuracy. In this case it may be desirable to ignore the first part of the simulation until the transient has settled. This parameter specifies the length of time to ignore at the start of the simulation before output samples start to be taken.

• Simulation end time: This parameter gives the maximum time for which the individual simulation will run. Normal and emergency stop simulations may end earlier if the rotor has stopped and any extra time has elapsed.

• Time to begin a stop: For normal and emergency stop simulations, this is the length of time for which normal running continues before the built-in stop logic is initiated.

• Extra simulation time after stopping: For normal and emergency stop simulations, the simulation may complete before the simulation end time. This can occur if the summation of the time taken to "complete" the shutdown and the extra time taken after shutdown is less than the simulation end time. Note however the shutdown is not considered "complete" until the rotor speed drops below a hardwired threshold of 0.6 \(\bunit{deg/s}\).

• Start time for turbulent wind: This applies to simulations which use a turbulent wind input. It modifies the turbulent wind start time at which the simulation will read the pre-computed turbulent wind time history.

This parameter controls the way the simulation results are output:

• Length of buffer: Simulation results are held in a buffer, which is periodically flushed to the disc. Enter the buffer length, in seconds of simulation time. The default is usually satisfactory. If viewing results while the simulation is in progress, a shorter buffer helps to ensure frequent updating, but it will slow down the simulation.

Last updated 23-09-2024