Contribute

How to contribute

You can add to the experimental database by contributing to our github repository. Refer to the spreadsheet to identify a data source that needs to be digitized and request edit access. If you have a specific document that you would like to work on that is not on the file, add an entry to the spreadsheet.

Please ensure that the data adheres to the database format. For guidance on how to digitize publicly available experimental data, please refer to the sections below.

Experimental Data Digitization

Sources

There are largely three ways that I have been using to obtain experimental airfoil pressure data: Google Scholar, Aerospace Research Central (ARC), and NASA Technical Reports Server (NTRS).

1. Google Scholar: In Google Scholar, you can essentially “google” existing papers. Use appropriate key words such as “airfoil pressure distribution”, “wind tunnel investigation”, etc. to find a wide variety of existing papers from different sources. Most of these will involve graphical plots of pressure data.
2. Aerospace Research Central: ARC is hosted by AIAA and will give you papers that they have hosted in AIAA conferences and journals. If you are part of an academic institution, you should likely have access to the database. The website is more focused than Google Scholar but has a good variety of all aerospace-related literature. As with Google Scholar, most of these will involve graphical plots of pressure data.
3. NASA Technical Reports Server: NTRS specifically hosts NASA’s technical reports. While these documents are often very old, they also provide the most extensive coverage of a variety high quality airfoil experiments. Most of the data has a combination of tabulated and graphical results. This lets you verify your digitization relatively easily. However, due to the age of many documents, the quality of the scanned PDFs may be poor.

Digitizing Tabulated Data

If the source material presents the experimental data in a tabulated format, I recommend that you use Optical Character Recognition (OCR) tools available online. Personally, I got best results from ExtractTable.

The workflow of using an OCR tool of your choice is as follows:

• Take a screenshot of the table that you want to digitize.
• In your choice of online OCR tool, upload the screenshot.
• When the conversion is complete, copy the data to clipboard and paste it into the csv file in Excel.
• Make sure the digitization was done accurately. Fix erroneous results as necessary.
• Rearrange the data into the previously described data format.

Digitizing Graphical Data

If the source material presents the experimental data in a graphical format (plot), I recommend that you use the online tool WebPlotDigitizer.

The workflow of using WebPlotDigitizer is as follows:

• Click Launch v5. You may need to create an account.
• Take a screenshot of the graph that you want to digitize.
• In WebPlotDigitizer, upload the screenshot: Files → Load Image(s).
• Calibrate the X- and Y-axes. Click on the minimum and maximum values of each axes and click Complete!. Then, enter their numerical values.
• Click on the plot points to digitize the data. Make sure you click the points in the order of: Trailing edge, upper surface → Leading edge → Trailing edge, lower surface.
• When finished, click View Data on the left and Copy to clipboard. Paste the result into the csv file in Excel.
• Make sure the digitization was done accurately. Fix erroneous results as necessary.
• Rearrange the data into the data format described earlier.

Notes

• In many cases, digitization is difficult due to poor legibility of tabulated data, the value should be determined indirectly by comparing it to the plotted results (if available), estimating based on the authors’ best knowledge of airfoil pressure distribution trends, or omitting the data point.
• In cases where digitization is difficult due to clustering of points at the leading and trailling edge, the data points should be carefully extracted by zooming in. This estimate should be informed by the authors’ knowledge of airfoil physics. If this is not viable, the point should be omitted.

Contributors

The authors would like to extend their thanks to the wonderful people below for the contributions to the ASPIRE digitization efforts!

• Aaditya Hingoo, Georgia Institue of Technology
• Ryan McKee, Georgia Institute of Technology
• Grant Ewing, Georgia Institute of Technology
• Bipin Koirala, Georgia Institute of Technology