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This page contains an interactive Java applet to explore the various factors which affect the lift of an airfoil. All of the information presented by the applet are available within the Beginner's Guide to Aerodynamics. You should start with the slide describing the factors that affect lift.

FoilSim III was released on July 27, 2010. The newest version of the FoilSim program calculates both the lift and drag of the Joukowsky family of airfoils, elliptical foils, flat surfaces, rotating cylinders and balls. The web page that you are now visiting houses the older FoilSim II program that ony calculates the lift.

This is a special, undergraduate, on-line version of the FoilSim II Java applet. If you are an experienced FoilSimU user, you can use the sleek version which does not contain the following instructions and loads faster on your computer.

FoilSimU includes all of the options of the original version plus some additional input and output panels. These panels are made available so that you can study the details of the conformal mapping used in the Kutta-Joukowski analysis. In the analysis, flow around a cylinder is mapped into flow around an airfoil. Using the Input choice box on the control panel, you can display a generating plane input panel. The panel contains four input variables which control the size and location of the generating cylinder relative to the poles of the transformation, and the strength of the point vortex which is embedded in the airfoil. According to the Kutta condition of the analysis, the strength of the vortex is set to bring the aft stagnation point to the trailing edge. With this version of FoilSim, you can turn the Kutta condition off by using the analysis choice box on the control panel to study the effect. A graph of the flow in the generating cylinder plane is also available using the Plot Selection option of the Output choice box on the control panel. A technical paper describing the details of this method is also available.

You can download your own copy of the undergraduate program by clicking on this yellow button:

Button to Download a Copy of the Program

There is an even more powerful version of FoilSimU which is available for very experienced users. This program is a Java application, not an applet. It runs stand alone and you must have Java installed on your computer to run this program. The chief advantage of this program is that it can write output files to your computer. You can obtain a copy of this program by pushing the yellow button shown above.


Button to Display Aerodynamics Index
Beginner's Guide to Aerodynamics
Beginner's Guide to Aeronautics
NASA Glenn Learning Technologies Home Page


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Editor: Nancy Hall
NASA Official: Nancy Hall
Last Updated: May 13 2021

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