2.4 Power coefficients calculation

1. Open the Demo_a project (if not open)
In Bladed, File > Open > demo_a.prj (this project is located within the Bladed application folder, e.g. C:\DNV\Bladed 4.18\DemoModels\Demo_a\demo_a.prj).

2. View the 'Performance Coefficients' calculation parameters
Calculations window > Main calculations > Steady state calculations > Double-click the Performance Coefficients to view it.

3. Define the calculation parameters
The defaults are ready to go but if you're confident why not change some of the parameters to investigate?

4. Run calculation
Click Run Now in the Calculations window.

5. Choose a Run Name and specify the location for the calculation output
In the Output settings window, try renaming the run using the Run Name field. Now select a sub-folder in the directory (you can either select the results folder, or create a new folder by editing the file path and typing the new folder's name).

6. Start the simulation
Click OK to run simulation.

1. Open Bladed Results Viewer
You can use the Windows search feature to find and launch the software.

2. Add calculations to view
Click the Add calculations button located near the left-hand corner. Find the performance coefficients calculation output file that you created earlier and click Open to add it.

3. Define an output to plot on the chart
Use the Output group dropdown to select the Performance coefficients. This will then display a list of variables below, select Power coefficient from the list. Now set the x-axis to the Tip speed ratio. Finally plot one of the pitch angles (e.g. -0.035) on the graph by double-clicking it.

4. Explore the graph
Right-click the mouse and hold to pan around the graph. Left-click and hold to draw a rectangle to zoom in on an area.
Can you find the optimum tip speed ratio for this pitch angle to maximize the power efficiency?

5. Define multiple outputs to plot on the chart
To do this return to the Select data to chart panel on the left hand side and locate the Pitch Angle output data. To select all of the options, left-click to select the first option on the list, while holding Ctrl select the last option in the list. Then click Add to chart to display all of the pitch angles. (If Add to chart is not enabled, select the Power coefficient again in the list of variable above and it should become enabled).

6. Zoom in on the peak of the curves by drawing a rectangle
See step 4 to remind you how to.

7. Find the the maximum power efficiency
Can you find the combination of Tip speed ratio and pitch angle that is giving the maximum power efficiency? You can select the line on the graph by left-clicking it, the line will appear bolder when selected and the corresponding details will be highlighted below the graph, telling you the pitch angle.

8. Export the data to get more precise values
On the right hand side just below the chart you will see an Export button. Click it and select Copy to clipboard. Open your preferred spreadsheet tool (we use Excel) and paste your data into a new spreadsheet.

9. Find the precise values for the power coefficient and tip speed ratio
Locate the column displaying the pitch angle that was determined in step 7. Now look down the column to help determine the maximum power coefficient (to narrow down your search, refer back to peak of the plot and where that range falls on the axis). Once you have found this you can find the corresponding Tip speed ratio in the first column.