The Calculation Window
The Calculations window lists all the available calculations, any one of which may be selected by clicking on it with the mouse. Next to each calculation is an indicator light. If this is green, the calculation may be performed. A red light indicates that no data is available to perform the selected calculation, while a yellow light indicates that some of the required data has been defined but not all.
Below the calculations is a small window showing all the data modules which need to be defined in order for the selected calculation to be performed. Double-clicking on one of these data modules immediately opens up the relevant screen in which the data for that module is defined. It is therefore a simple matter, having selected the calculation to be performed, to work through all required data modules which are still undefined and assign the relevant data.
Sequence of operations
Before any turbine calculations can be done, it is necessary to specify the principal characteristics of the blades and rotor. Open the relevant screens by one of the means described above, for instance from the Specify pull-down menu, from the relevant Toolbar icon, or from the Calculations screen with one of the turbine calculations selected.
To be able to define the aerodynamic characteristics of the blades, it is necessary to enter or import the relevant aerofoil
datasets into the aerofoils database if it is not already present, using the Aerofoil icon on the toolbar, or from the Specify pull-down menu.
It is also necessary to define the following modules:
Physical constants (although standard values will have been defined by default)
Aerodynamics control
Calculation definition depending on which calculation is selected (further parameters specific to the selected calculation)
These are all on the Calculation Parameters screen, accessible from the Calculations screen or from the Specify pull-down menu on the toolbar.
Having defined this fundamental data, it should then be possible to perform the following steady state turbine calculations at a fixed rotational speed and pitch angle defined on the Calculation definition screen specific to each calculation:
Aerodynamic information (to examine the aerodynamics at each blade station, such as lift and drag, inflow, tip loss and so on. at a specified wind speed)
Performance coefficients (dimensionless power, torque and thrust coefficients as a function of tip speed ratio)
Power curve (at specified fixed rotor speed and pitch angle).
These calculations are quick and the results can instantly be examined graphically using the Data View icon on the toolbar. From the power curve, the annual energy yield can also be calculated. This is one of the post-processing calculations, and again the results can be seen using Data View.
The Outputs button on the Calculations screen allows the user to specify in some detail which loads and other outputs are desired. Once this is done, the Steady-state operational and parked loads calculations can also be carried out (at specified fixed rotor speed and pitch angle), and Data View used to see the results.
At the preliminary design stage, various turbine parameters can be adjusted and all these calculations can be repeated rapidly until satisfactory results are obtained.
As further data is defined, more complex calculations can be carried out. For example, by defining suitable combinations of drive train, generator and control characteristics, it becomes possible to calculate the steady power curve and steady operational loads with the rotor speed and/or pitch angle varying with wind speed as appropriate.
After defining the numbers of vibrational modes on the Flexibility Modeller screen, along with the necessary mass and stiffness
information as indicated on the Calculations screen, it becomes possible to perform a Modal analysis calculation. Blade and tower
bending can then be taken into account in the calculations.
Simulations can also be performed once the Simulation control and Time varying windseastate modules are defined. As always, the minimum data required is always indicated on the Calculations screen, making it easy to ensure that the necessary data is defined for each calculation to be done.
Note also the Show options button at the bottom of the Calculations screen. This provides a rapid means of switching particular features off or on for a particular calculation. For example, provided the energy losses module has been defined, the energy losses
can be switched off or on very easily using this feature, for all calculations where energy losses are actually relevant.
Performing Calculations
Calculations may be initiated either from the Calculations pull-down menu on the toolbar, or from the Calculations window by clicking the Run Now button. For some of the steady state calculations and all the simulations, the Calculations window also gives access to facilities for switching various calculation options on or off, and for specifying the calculation outputs required. Post-processing calculations may also be initiated using the Execute button in the post-processing window obtained by clicking the Analyse icon on the toolbar.
The user can also select Run in Batch to store the calculation for later execution by the batch facility. Except for certain calculations, a window appears in which a directory can be selected into which the calculation outputs will be placed. If the directory does not exist, it will be created. A run name is also required. Thus a number of calculations may be placed in the same directory, each with a different run name.
Long calculations may be stacked up using the Run in Batch button in the Calculations window. The whole batch of calculations may then be started so that they run one after the other, for example overnight. This is done using the Batch` menu item on the toolbar.
Except for some auxiliary calculations, the user will be asked to specify where the calculation outputs are to be sent. A dialogue box allows the drive and directory to be selected, and a run name must also be specified. This is used to identify all the output files produced by that calculation. A new output directory may be created by editing the directory name.
While the calculation is running, a window appears which displays a progress bar showing how far the calculation has progressed, together with any warnings which may arise during the calculation. An 'Abort' button allows the user to stop a calculation which is in progress. Any part-written output files which have already been produced should be available. This means that a long simulation can be stopped without losing the results which have so far been produced.
There is also the option to select ASCII or binary format for the calculation results. Binary format gives much smaller files, and should be faster and more accurate. Graph plotting, post-processing and tabulation all work with either format. If you want to see the raw numbers from binary files, you can still tabulate the numbers (to the screen, an ASCII file, Excel or Word).
Process Priority: On later Windows versions, selecting Low priority will prevent the batch calculations from slowing down other user actions.
Tip
If a whole series of calculations is to be performed, for example a set of simulations for different load cases which might include stops and starts as well as normal running and parked conditions in a series of different wind conditions, some thought should be given to the directory structure used, and the file extensions used within each directory. For example a tree structure could be used with a sub-directory for each group of load cases. Each individual load case could then be in its own sub-directory, or different extensions could be used within the directory, for example to indicate different mean windcurrent speeds. Bear in mind also the need for post-processing results to be stored for each load case. Some post-processing results may also be summed over a series of load cases.
Calculations may also be set off from the Calculations pull-down menu on the toolbar. Post-processing and supporting calculations may also be set off from the relevant data entry screen.
Data Required for Calculations
Alongside each calculation is a coloured light showing whether the calculation can be performed:
Red light: No data available: no calculation possible
Yellow light: Some data available: no calculation possible
Green light: Sufficient data has been defined to perform the calculation
The box below shows all the data items required for the calculation, and indicates whether the relevant data has been defined or not. Double-clicking on any data item which is undefined opens the appropriate window so that the required data can be defined.
Calculation Parameters
Click the Calculation parameters button on the Calculations screen to define the parameters for controlling particular calculations. These include general parameters as well as parameters for defining specific calculations.
General parameters:
Aerodynamics control: to define the aerodynamic modelling parameters.
Simulation control: to define how a simulation will proceed.
Imbalances: to specify mass and aerodynamic imbalances.
Initial conditions: the rotor azimuth and nacelle yaw position at the start of a simulation can be defined.
Calculation Options
A number of machine and wind features, once defined, are available as options which can be switched on or off in some of the steady state
calculations and simulations. Click the Show Options button in the bottom left corner.
Use the check boxes to switch on or off any desired option, provided it is available for the selected calculation. If a red or yellow dot is displayed, the option will not be used even if selected, as the necessary data has not been defined: click on the option name to display all the required data items in the box below. Double-clicking on any data item which is undefined opens the appropriate window so that the required data can be defined.
Specifying Calculation Options
A number of machine and wind features, once defined, are available as options which can be switched on or off in some of the steady state
calculations and simulations. Click the Show Options button in the bottom left corner of the Calculations screen to display the options. The screen expands to show a list of the available options, with an indicator for each to show whether it can be used, as follows:
No light (grey): This option is not available for the selected calculation.
Red light: No data available: option will not be used even if selected.
Yellow light: Some data available: option will not be used even if selected.
Green light: Sufficient data is defined for the option to be used if selected.
Initially, all options are switched on by default, but if any are switched off for a given calculation, the setting will be remembered. An option displaying a yellow or red light will not be used even if selected. The options available are:
Energy losses. Allows user to enable or disable electrical losses and mechanical losses.
Passive yaw motion. This option enables/disables yaw motions options.
Imbalances and Faults.
Last updated 15-11-2024