Computational analysis of airfoils in ground effect for use as a design tool

There has been interest shown in a recreational glider which operates primarily in the flight regime known as ground effect. Ground effect traditionally occurs when the airfoil is within a chords length of the ground. It is well known in the art that when the airfoil is present in ground effect the lift force is increased and the drag force is reduced on the lifting surfaces, in turn increasing the L/D ratio.;This recreational glider would have no internal power supply and only rely on the outside acting force. The considered force that would be used to propel this recreational glider would be the force of gravity pulling the craft down an incline. An incline such as this can be found at numerous ski resorts all over the world. The recreational glider could be used at these ski resorts year round and help solve revenue issues for ski resorts during the off season and provide a new recreational sport.;One of the major design aspects in designing the recreational glider is selecting an airfoil which will provide adequate lift in order to keep the craft airborne. At the same time this airfoil must allow for the most stable flight while maintaining the appropriate altitude in order to take advantage of the enhanced aerodynamic characteristics present in ground effect flight. After the airfoil that would be used in the first design of the recreational glider was selected the airfoil performance was tested in Computational Fluid Dynamics (CFD). In order for this data to be trusted enough to invest the time and money into wind tunnel testing the CFD research needed validation. These results were then compared to the CFD results of previous experimental results.;Preliminary analysis indicated the Wortmann FX 63-137 provided a good first approximation and thus was analyzed for angles of attack of 0 to 6 degrees with height-to-chord ratios from 0.05 to 1, which determines the ground clearance of the airfoil. The airfoil was analyzed with the results obtained focused on the coefficient of lift, coefficient of drag, and the x-location of the center of pressure.;The CFD results showed that ground effect did increase the lift coefficient as the distance the airfoil above the ground was reduced. The results also showed that the drag coefficient was reduced as the distance the airfoil above the ground was reduced. These results were very evident at angles of attack of 4 and 6 degrees, and began to appear at an angle of attack of 2 degrees or less. The stability of the airfoil was also monitored by locating the center of pressure for the various angles of attack and altitudes. The center of pressure did not make any sudden shifts in location, instead making a slight move along the chord when the airfoil changed angles of attack.;This work leads to the following conclusions, and that was that the Wortmann FX 63-137 did show the increase in lift and reduction in drag when operating in ground effect that was expected, as well as minimal movement in the center of pressure along the chord length. This means that the airfoil can remain the initial airfoil to be used in the recreational glider, and proceed to experimental testing in order to verify the CFD results from this study