Simulation Module Overview

Visualization of an aero-hydro-servo-elastic simulation in QBlade.

Fig. 81 Visualization of an aero-hydro-servo-elastic simulation in QBlade.

To define a simulation of a turbine object several simulation parameters and boundary conditions need to be defined. The following list gives an overview:

  • Simulation length & time step size

  • Structural solver

  • Wind boundary conditions

  • Wave & current boundary conditions

  • Environmental parameters: density, gravity, etc.

Simulations can either be defined through the turbine simulation dialog, or directly by creating or modifying simulation definition (.sim) files.

Simulation Definition Dialog

Setting up a simulation in QBlade is handled through the dialog shown below:

Part 1 of the simulation definition dialog.

Fig. 82 Part 1 of the simulation definition dialog.

Part 2 of the simulation definition dialog.

Fig. 83 Part 2 of the simulation definition dialog.

Part 3 of the simulation definition dialog.

Fig. 84 Part 3 of the simulation definition dialog.

Part 4 of the simulation definition dialog.

Fig. 85 Part 4 of the simulation definition dialog.

Part 5 of the simulation definition dialog.

Fig. 86 Part 5 of the simulation definition dialog.

Below, an overview of the different dialog sections and their editable parameters is given:

General Simulation Settings

  • Name of Simulation: A unique name to identify the simulation object

  • Timestep Size / Azimuthal Step: Both values are interconnected through the turbine RPM setting

  • Number of Timesteps / Simulation Length: Both values are interconnected through the TimestepSize setting

  • Store Replay: A replay of the simulation is created by storing all position and wake data for every timestep.

Structural Model Initialization

These field are only editable if the selected turbine object has a structural model definition.

  • Ramp-Up Time: The (structural) simulation is ramped-up over the specified time. This part of the simulation does not generate data and is not stored.

  • Initial Overdamp. Time: For the specified time the model Rayleigh damping is increased by the factor Overdamp. Factor. If the value is 0 the overdamping is active during ramp-up, any negative value disables overdamping of the model.

  • Overdamp. Factor: During the overdamping time all model damping values are increased by this factor.

Wind Boundary Condition

  • Wind Input Type: Sets the wind input type. Options are Uniform Wind Field, Turbulent Wind Field and Hub Height File.

  • Turbulent Windfields: In this ComboBox all Windfields that are stored in the database are listed.

  • Turbulent Windfield Object: These buttons allow to generate a new Windfield or to edit an existing one.

  • Turbulent Windfield Shift: The currently selected Windfield may be shifted in time (to start at another time than t=0s), if Auto is chosen the Windfield is shifted by the rotor diameter divided by the mean freestream velocity to fully immerse the rotor at the start of a simulation..

  • Turbulent Windfield Stitching: If the simulation time is larger than the Windfield length the Windfield is either repeated (Periodic) or mirrored (Mirror) at the end of its timeseries.

  • Aerodyn Hub Height File: This enables to load a hub height file from the file system to be assigned to this simulation.

  • Windspeed: Set the windspeed if Wind Input Type is set to Uniform.

  • Vert. Inflow Angle: Set the vertical inflow angle if Wind Input Type is either Uniform or Turbulent Field.

  • Horiz. Inflow Angle: Set the horizontal inflow angle if Wind Input Type is either Uniform or Turbulent Field.

  • Wind Shear Type: Set the windshear type if the wind input type is Uniform or the turbulent windfield is imported.

  • Power Law Exponent: Set the Coefficient for a Power Law wind profile.

  • Roughness Length: Set the Roughness Length for a Log Profile..

  • Reference Height: Set the Reference Height for the wind profiles.

  • Directional Shear: Set a directional shear. The shear is assumed to be 0.0 at the Reference Height.

  • Include Ground Effects: Interludes the modelling of Ground Effects, see Ground Effect.

Turbine Setup

  • Name of Turbine: Define a name for the turbine simulation object.

  • Use Turbine Definition: Use the selected turbine definition object from the data base in this simulation object.

  • Position (X,Y,Z): Set the global position of the wind turbine for this simulation.

Rotational Speed Settings

  • RPM / TSR: Both values are interconnected through the rotor size and current windspeed.

The following options are related to the RPM control for this simulation. For turbine definition object without a structural definition the RPM is always constant if no Simulation Input File is defined. For turbine definition objects with a structural definition the following options are avaliable:

  • Ramp-Up Fixed: The RPM is fixed only during the ramp-up time of the simulation so that when the simulation starts the rotor is operating at the chosen RPM. During the simulation time the rotor rotation is governed by the balance of aerodynamic- and generator torque. This is the recommended setting for simulations that contain a Controller.

  • Always Fixed: The RPM is fixed for the total duration of the simulation to the chosen RPM.

  • Free: For ramp-up and simulation time the rotor rotation is governed by the balance of aerodynamic- and generator torque.

Turbine Initial Conditions

  • Azimuth, Yaw, Col. Pitch: Sets the initial azimuthal rotor angle, yaw angle and collective pitch angle for the simulation.

Floater Initial Conditions

These edits are only enabled if a wind turbine with a floating substructure is simulated. The initial floater conditions can be used to setup decay tests for specific DOF’s or to place the floater closer to its final equilibrium position to speed-up initial transients.

  • X, Y, Z Translation: Sets the initial displacement for the floater.

  • Roll, Pitch, Yaw: Sets the initial rotation of the floater.

Structural Simulation Settings

  • Structural Steps / Aerostep: Sets how many structural steps will be evaluated per global timestep. If multiple structural steps are evaluated per global timestep the aerodynamic loading is assumed to be constant.

  • Initial Relaxation Steps: An initial iterative relaxation is performed, taking into account only gravitational forces.

  • Number of Iterations: Set the number of iterations for the iterative time steppers, such as the HHT.

  • Include Aero Forces & Moments: Toggles if aerodynamic forces are projected onto the structural model definition.

  • Include Hydro Forces & Moments: Toggles if hydrodynamic forces are projected onto the structural model definition.

Turbine Behavior

In this section special events, external loading, prescribed motion and prescribed operation can be defined for a turbine definition. Below exemplary files are shown for each file type:

  • Event Definition File: An event is defined by a combination of Keywords and values. The following list gives an overview of the available event types. Events can only be defined if the turbine definition has a structural definition. Multiple events may be defined in a single file. The events override any events / control that is returned via the controller exchange array:

    • 30 FAILGRID: At time 30 s, the generator moment is set to 0 Nm.

    • 30 SETBRAKE: At time 30 s, the brake is engaged.

    • 30 1.5 FAILPITCH_1: At time 30 s, the pitch rate of blade nr. 1 is set to a maximum rate of 1.5 deg/s

    • 30 90 1.5 PITCHTO: At time 30 s, the collective pitch rate is set to 1.5deg/s until 90 deg are reached.

    • 30 90 1.5 YAWTO: At time 30 s, the yaw rate is set to 1.5deg/s until 90 deg are reached.

    • 30 FAILBLADE_1: At time 30 s, blade nr. 1 is released from the hub, by deactivating the respective structural constraint.

    • 30 FAILCABLE_1: At time 30 s, the cable with the IDNr. 1 brakes away from the substructure.

  • External Loading File: A user defined loading timeseries can be applied to the turbine during simulation via this file format, multiple loading timeseries may be appended into a single file. The nomenclature in the file is as follows:

<SensorName> <localflag>
<time1> <fx1> <fy1> <fz1> <mx1> <my1> <mz1>
<time2> <fx2> <fy2> <fz2> <mx2> <my2> <mz2>

Sensor naming is the same as in the main file for the sensor outputs (see Loading Data and Sensor Locations) The local flag (local, global) defined if the loads are applied in the Global Coordinate System or in the Local Body Coordinate Systems or Local Sensor Coordinate Systems. QBlade interpolates linearly the loads between time stamps. External load time series for multiple sensors can be appended into a single file.

  • Simulation Input File:

The turbine operation can be prescribed using a file of the following format. Turbine definition with or without a structural definition can be subjected to prescribed operation. QBlade interpolates linearly the loads between time stamps.

Time    RPM     Yaw     PitchB1 PitchB2 ...     PitchBN AFC1_B1 AFC2_B2 ...     AFCN_BN
0       1       11      0       0       ...     0       0       0       ...     0
5       2       11      0       0       ...     0       0       0       ...     0
10      4       11      0       5       ...     0       0       0       ...     0
15      7       11      0       10      ...     0       0       0       ...     0
20      11      11      0       17      ...     0       0       0       ...     0
25      12      11      0       27      ...     0       0       0       ...     0
30      13      11      0       40      ...     10      0       0       ...     0
35      12      11      0       40      ...     20      0       0       ...     0
40      11      11      0       40      ...     30      0       0       ...     0
45      11      11      0       40      ...     40      0       0       ...     0
50      11      11      0       40      ...     40      0       0       ...     0
  • Prescribed Motion File

The turbine location and orientation can be prescribed using a file of the following format. Turbine definition with or without a structural definition can be subjected to prescribed operation. QBlade interpolates linearly the loads between time stamps.

Time    RPM     Yaw     PitchB1 PitchB2 PitchB3
0       1       11      0       0       0
5       2       11      0       0       0
10      4       11      0       5       0
15      7       11      0       10      0
20      11      11      0       17      0
25      12      11      0       27      0
30      13      11      0       40      10
35      12      11      0       40      20
40      11      11      0       40      30
45      11      11      0       40      40
50      11      11      0       40      40

Multi Turbine Simulations

QBlade-EE

This feature is only available in the Enterprise Edition of QBlade.

If enabled multiple turbines may be added to a single simulation object and their wake interaction can be evaluated.

Turbine Environment

  • Installation: The user can chose between Offshore and Onshore installation. If Offshore is selected the user must also specify the water depth.

  • Water Depth: Sets the water depth for an offshore simulation.

Wave Boundary Conditions

These edits are only enabled if Offshore installation is selected.

  • Wave Type: Toggles if a linear wave should be included in the simulation.

  • Kinematic Stretching: Choose the Kinematic Stretching type if a linear wave is selected.

  • Linear Wave: A wave from QBlades database can be selected.

  • Linear Wave Object: The currently selected wave object can be edited or a new wave object can be created.

Ocean Current Boundary Conditions

  • Near Surf: U, Dir, Dep: Sets velocity, direction and depth parameters for Near Surface Currents, see Currents.

  • Sub Surf: U, Dir, Exp: Sets velocity, direction and exponent parameters for Sub Surface Currents, see Currents.

  • Near Shore: U, Dir: Sets velocity and direction for Near Shore Currents, see Currents.

Environmental Variables

The user can set the environmental parameters that are used during the simulation and for the evaluation of several quantities such as Reynolds Number or Keulegan-Carpenter Number. The list of environmental parameters is shown below:

  • Gravity

  • Air Density

  • Kinematic Viscosity (Air)

  • Water Density

  • Kinematic Viscosity (Water)

Seabed Modelling

To prevent the mooring lines from penetrating the seabed, the seabed is modelled as vertically oriented spring/dampers that act on the mooring line elements that are in contact with the seabed. The model implemented is highly similar to the work of Hall1.

  • Seabed Stiffness: The spring stiffness coefficient for the seabed model (acting in the vertical direction only).

  • Seabed Damping Factor: The seabed damping coefficient, as a fraction of the spring stiffness coefficient (acting in the vertical direction only).

  • Seabed Fraction Factor: The seabed fraction coefficient for the seabed model, as a fraction of the spring stiffness coefficient (acting in the horizontal direction, opposite to the direction of line movement, only).

Stored Simulation Data

The uer can choose here to only store a certain type of simulation data (to limit the project file or data export size. Furthermore, the user can choose to store simulation data only after a certain time has passed, to remove transients from the datasets.

  • Store Output From: Simulation Data is only stored after the defined simulation time has passed.

  • Store Aero Time Data: Toggles if this data type is stored. (All data that is shown in the Aerodynamic Time Graph).

  • Store Aero Blade Data: Toggles if this data type is stored. (All data that is shown in the Aerodynamic Blade Graph).

  • Store Structural Data: Toggles if this data type is stored. (All data that is shown in the Structural Time Graph).

  • Store Hydrodynamic Data: Toggles if this data type is stored. (All data that is shown in the Hydrodynamic Time Graph).

  • Store Controller Data: Toggles if this data type is stored. (All data that is shown in the Controller Time Graph).

VPML Particle Remeshing

QBlade-EE

This feature is only available in the Enterprise Edition of QBlade.

Free wake filaments may be converted into vortex particles. The following parameters govern the treatment of free vortex particles during a simulation.

  • Remeshing Scheme

  • Remesh Update After X Steps

  • Base Grid Size

  • Particle Core Size Factor

  • Magnitude Filter Factor

  • Max. Stretch Factor

Ice Throw Simulation

QBlade-EE

This feature is only available in the Enterprise Edition of QBlade.

A simulation of ice throw, shed from the rotor, can be performed in QBlade, see Lennie and Marten2. The following parameters govern the range of the randomized uniform distributions of ice particle properties. The distribution of landed ice particles can then be exported to generate iso-risk contours for the localized individual risk (LIRA) of a person being hit by an ice throw event.

  • Simulate Ice Throw: Toggles if an Ice Throw Simulation is carried out.

  • Min. / Max. Drag: Sets the range of drag values for the generated ice particles.

  • Min. / Max. Mass: Set the range of masses for the generated ice particles.

  • Min. / Max. Density: Set the range of density for the generated ice particles.

  • Min. / Max. Radius: Set the range of ice particle release positions (in % of rotor radius).

  • Total N Particles: Set the total number of ice particles that are generated during the simulation. This number will be evenly distributed over all timesteps of the simulation.

Multi-Threaded Batch Analysis

QBlade-EE

This feature is only available in the Enterprise Edition of QBlade.

Multiple simulations can be evaluated in a parallel batch queue through the dialog Menu->Turbine Simulation->Multi-Threaded Batch Analysis. The simulations are selected from a list in the dialog (see Fig. 87). After choosing the number of parallel threads the batch analysis starts by clicking the Start Batch button.

The Multi-Threaded Batch Analysis Dialog.

Fig. 87 The Multi-Threaded Batch Analysis Dialog.

Simulation Export

Simulation objects can be exported into the text based .sim format. When a simulation object is exported into the .sim format, the associated turbine .trb file is automatically generated and exported. See an exemplary .sim file below:

----------------------------------------QBlade Simulation Definition File------------------------------------------
Generated with : QBlade IH v2.0.2_alpha windows
Archive Format: 310003
Time : 17:22:16
Date : 29.06.2022

----------------------------------------Object Name-----------------------------------------------------------------
IEA_15MW_TURB-UBEM222                    OBJECTNAME         - the name of the simulation object

----------------------------------------Simulation Type-------------------------------------------------------------
0                                        ISOFFSHORE         - use a number: 0 = onshore; 1 = offshore

----------------------------------------Turbine Parameters---------------------------------------------------------
multiple turbines can be added by adding multiple definitions encapsulated with TURB_X and END_TURB_X, where X must start at 1

TURB_1
    IEA_15MW_ASE_UBEM/IEA_15MW_ASE_UBEM.trb TURBFILE           - the turbine definition file that is used for this simulation
    IEA_15MW_ASE_UBEM                    TURBNAME           - the (unique) name of the turbine in the simulation (results will appear under this name)
    0.00                                 INITIAL_YAW        - the initial turbine yaw in [deg]
    0.00                                 INITIAL_PITCH      - the initial collective blade pitch in [deg]
    0.00                                 INITIAL_AZIMUTH    - the initial azimuthal rotor angle in [deg]
    1                                    STRSUBSTEP         - the number of structural substeps per timestep (usually 1)
    20                                   RELAXSTEPS         - the number of initial static structural relaxation steps
    0                                    PRESCRIBETYPE      - rotor RPM prescribe type (0 = ramp-up; 1 = whole sim; 2 = no RPM prescibed)
    2.000                                RPMPRESCRIBED      - the prescribed rotor RPM [-]
    10                                   STRITERATIONS      - number of iterations for the time integration (used when integrator is HHT or Euler)
    1                                    MODNEWTONITER      - use the modified newton iteration?
    0.00                                 GLOBPOS_X          - the global x-position of the turbine [m]
    0.00                                 GLOBPOS_Y          - the global y-position of the turbine [m]
    0.00                                 GLOBPOS_Z          - the global z-position of the turbine [m]
                                         EVENTFILE          - the file containing fault event definitions (leave blank if unused)
                                         LOADINGFILE        - the loading file name (leave blank if unused)
                                         SIMFILE            - the simulation file name (leave blank if unused)
                                         MOTIONFILE         - the prescribed motion file name (leave blank if unused)
END_TURB_1

----------------------------------------Simulation Settings-------------------------------------------------------
0.050000                                 TIMESTEP           - the timestep size in [s]
1600                                     NUMTIMESTEPS       - the number of timesteps
10.000                                   RAMPUP             - the rampup time for the structural model
0.000                                    ADDDAMP            - the initial time with additional damping
100.000                                  ADDDAMPFACTOR      - for the additional damping time this factor is used to increase the damping of all components
0.000                                    WAKEINTERACTION    - in case of multi-turbine simulation the wake interaction start at? [s]

----------------------------------------Wind Input-----------------------------------------------------------------
1                                        WNDTYPE            - use a number: 0 = steady; 1 = windfield; 2 = hubheight
Windfield.bts                            WNDNAME            - filename of the turbsim input file or hubheight file (with extension), leave blank if unused
1                                        STITCHINGTYPE      - the windfield stitching type; 0 = periodic; 1 = mirror
0                                        WINDAUTOSHIFT      - the windfield shifting automatically based on rotor diameter; 0 = false; 1 = true
11.00                                    SHIFTTIME          - the windfield is shifted by this time if WINDAUTOSHIFT = 0
10.00                                    MEANINF            - the mean inflow velocity, overridden if a windfield or hubheight file is use
0.00                                     HORANGLE           - the horizontal inflow angle
0.00                                     VERTANGLE          - the vertical inflow angle
0                                        PROFILETYPE        - the type of wind profile used (0 = Power Law; 1 = Logarithmic)
0.200                                    SHEAREXP           - the shear exponent if using a power law profile, if a windfield is used these values are used to calculate the mean wake convection velocities
0.010                                    ROUGHLENGTH        - the roughness length if using a log profile, if a windfield is used these values are used to calculate the mean wake convection velocities
0.00                                     DIRSHEAR           - a value for the directional shear in deg/m
150.00                                   REFHEIGHT          - the reference height, used to contruct the BL profile

----------------------------------------Ocean Depth, Waves and Currents-------------------------------------------
the following parameters only need to be set if ISOFFSHORE = 1
1.00                                     WATERDEPTH         - the water depth
                                         WAVEFILE           - the path to the wave file, leave blank if unused
0                                        WAVESTRETCHING     - the type of wavestretching, 0 = vertical, 1 = wheeler, 2 = extrapolation, 3 = none
20000.00                                 SEABEDSTIFF        - the vertical seabed stiffness [N/m^3]
0.50                                     SEABEDDAMP         - a damping factor for the vertical seabed stiffness evaluation, between 0 and 1 [-]
0.00                                     SEABEDSHEAR        - a factor for the evaluation of shear forces (friction), between 0 and 1 [-]
0.00                                     SURF_CURR_U        - near surface current velocity [m/s]
0.00                                     SURF_CURR_DIR      - near surface current direction [deg]
30.00                                    SURF_CURR_DEPTH    - near surface current depth [m]
0.00                                     SUB_CURR_U         - sub surface current velocity [m/s]
0.00                                     SUB_CURR_DIR       - sub surface current direction [deg]
0.14                                     SUB_CURR_EXP       - sub surface current exponent
0.00                                     SHORE_CURR_U       - near shore (constant) current velocity [m/s]
0.00                                     SHORE_CURR_DIR     - near shore (constant) current direction [deg]

----------------------------------------Global Mooring System------------------------------------------------------
                                         MOORINGSYSTEM      - the path to the global mooring system file, leave blank if unused

----------------------------------------Environmental Parameters---------------------------------------------------
1.22500                                  DENSITYAIR         - the air density
0.000016468                              VISCOSITYAIR       - the air kinematic viscosity
997.00000                                DENSITYWATER       - the water density
0.000001307                              VISCOSITYWATER     - the water kinematic viscosity
9.806650000                              GRAVITY            - the gravity constant

----------------------------------------Output Parameters----------------------------------------------------------
0                                        STOREREPLAY        - store a replay of the simulation: 0 = off, 1 = on (warning, large memory will be required)
20.000                                   STOREFROM          - the simulation stores data from this point in time, in [s]
1                                        STOREAERO          - should the aerodynamic data be stored (0 = OFF; 1 = ON)
1                                        STOREBLADE         - should the local aerodynamic blade data be stored (0 = OFF; 1 = ON)
1                                        STORESTRUCT        - should the structural data be stored (0 = OFF; 1 = ON)
0                                        STOREHYDRO         - should the controller data be stored (0 = OFF; 1 = ON)
0                                        STORECONTROLLER    - should the controller data be stored (0 = OFF; 1 = ON)
----------------------------------------Modal Analysis Parameters--------------------------------------------------
0                                        CALCMODAL          - perform a modal analysis after the simulation has completed (only for single turbine simulations)
0.00000                                  MINFREQ            - store Eigenvalues, starting with this frequency
0.00000                                  DELTAFREQ          - omit Eigenvalues that are closer spaced than this value
1

M. Hall. Efficient modelling of seabed friction and multi-floater mooring systems in moordyn. Proceedings of the 12th European Wave and Tidal Energy Conference, 2017:1, 2017. URL:, doi:.

2

S. Lennie, M. Dominin and D. Marten. Development of ice throw model for wind turbine simulation software qblade. AIAA Scitech 2019 Forum, 2019. URL: https://arc.aiaa.org/doi/abs/10.2514/6.2019-1800, doi:10.2514/6.2019-1800.