Paul Nelson, Chad LeBaron, Bart Frischknecht, Kristopher Danielson and Jerry Bowman, Mechanical Engineering
Very little aerodynamic data exists for Reynolds numbers less than 100,000. It is common for there to be a large discrepancy between numerically predicted and experimental airfoil performance, especially at very low Reynolds numbers. In this research, a low Reynolds number airfoil was developed based on aerodynamic measurements.
The first stage of our research was to perform low Reynolds number airfoil testing. Few facilities exist in the world that can make the measurements required. BYU has a wind tunnel facility that can be used for low Reynolds number testing. The airfoil and wing tests in the wind tunnel helped to develop a more effective MAV airfoil. The collected Reynolds number data were used to determine vital aerodynamic properties such as lift, drag, pitching moment, and lift to drag ratio. These aerodynamic properties were critical in designing an efficient MAV airfoil.
Wind tunnel testing was performed using a four strain gauge based force transducer. This data acquisition system was used in the wind tunnel to measure lift and drag forces on various airfoil designs at several velocities and angles of attack.
The most efficient MAV designs exhibited the characteristics of a flying wing rather than those of a traditional aircraft. We determined that the airfoil must produce a good lift to drag ratio at Reynolds numbers around 70,000-90,000.
With all of this gathered data and extended analysis using various software packages, we successfully decreased the size of our MAVs. We entered these smaller, more efficient MAVs in the 6th Annual International MAV Competition. With our help, BYU took 1st place in the Design Competition. We placed 3rd in the Surveillance Competition. BYU also placed 1st in the Endurance Competition. BYU had the smallest plane to fly at the competition. The largest linear distance of that plane was 4.375 inches and flew for 1.05 minutes.
Our research helped to advance BYU’s ongoing effort to achieve smaller and smaller flight. Much work is still left to be accomplished in the design of these MAVs.
This research will continue with the mechanical engineering department in the future. Teams are organized on a continual basis for the annual competitions and under their direction the research will continue. This research opportunity required great discipline and teamwork. We met on an almost weekly basis to discuss our findings and ways in which we could improve upon our designs. I plan to continue the pursuit of smaller and more efficient MAVs as a hobby in the future.