Friday, November 8, 2013

Experimenting with NASA FoilSim Website

I have been interested in the more technical side of my hobbies and projects lately and took another look at the FoilSim program on the NASA website.  Your computer needs an update to current version of Java to run and there could be a splash screen about a risk to accept on to get things started.  Through your web browser many aspects of airfoil performance can be simulated in an interactive manner. There is a disclaimer stating that it is for educational purposes and not for designing aircraft.

Link to FoilSim:

Opening Screen with Default Values

To start with I used default values which provide a wing of 100 square feet flying at 100 mph then I selected the flat bottom airfoil and the flat plate airfoil. Next I started increasing the angle of attack from zero in one degree increments, output data from this included amount of lift, drag, and L/D. To me it was interesting to note that L/D increased until about 3 degrees and then started to diminish. Which means at this point the drag of the wing is increasing faster than the lift.

Starting at 0 Degrees with Flat Bottom Airfoil

Increasing to 3 Degrees

The same data was entered for a wing that might be typical for a small model airplane with a wing area of only 1 square foot flying at 15 mph. Output was somewhat different but followed the same basic pattern. Calculations were also done for the flat plate airfoil.

Changing to Model Size Wing Section

For me this is interesting because I had read many books on model aircraft design theory and it was fun to see the theory simulated. For one degree value of the model size wing I changed the aspect ratio from 4 to almost 8 to see the change in L/D, it improved considerably as predicted.  My data and some of the output were entered in an Excel spreadsheet manually.  Take a look at this fun simulator.

Entering Data into Excel

Bill Kuhl

For an explanation of many aspects of simple aerodynamics with math problems check out my article Basic Aerodynamics With a Lesson

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