Darius Carter, a researcher under Dr. Eric Loth, presented his findings at UVA’s research symposium on July 2th. Below is Darius’ description of his work.
Designing an experimental set up to investigate Insect fouling on a hot airfoil.
By Darius Carter, Dr. Eric Loth
Fluid Research and Innovations Lab (FRIL) at University of Virginia
Leading edge contamination on aircraft wings can occur through the accumulation of insect residues. These can then increase drag by causing an earlier transition of the boundary layer from laminar to turbulent flow. However, the temperature of the air and leading edge have never been investigated despite the fact that insect fouling mostly occurs during the summer. The goal of the project is investigating performance of a nano-coating that can withstand high speed (100 mph) insect impacts and hot temperature (100 F) airfoil surface. The experimental set up included a wind tunnel, a heat sheet, and a NACA 0038R airfoil with a cylindrical leading edge. To determine typical residue height for insect impacts, experimental tests were conducted with live flightless fruit flies (Drosophila melanogaster). The fruit flies were launched in the wind tunnel through a clear plastic tubing using the Venturi principle which can cause suction as well as propel them at high speeds with just air pressure. The coating that was optimized had to have Nano-scale roughness and was also super hydrophobic to leave the least amount of insect residues. Using this new experimental set up, detailed investigations will be completed in the near future. The results can lead to a future of aircrafts that have natural laminar flow (NLF) wings which can decrease cruising flight fuel consumption.
Aircraft leading edges are subjected to harsh environments and exposed to different types of contamination such as insect, ice, sand, dust and other foreign particulates. Insect contamination on the leading edge surfaces can lead to earlier transition of the boundary layer from laminar to turbulent flow due to the introduction of instabilities in the flow caused by the insect residue. Leading edge contamination can increase the drag of the wings if the flow prematurely transitions to turbulent flow for aircraft designed with natural laminar flow (NLF) wings [1-2]. Hence, researchers have started investigating insect fouling in order to reduce the effect on laminar wing aircraft performance. Previous studies have identified the degree of insect fouling from flight observations and wind tunnel testing . However, this studies do not take in to account the environmental conditions the airplanes are in during summer take-offs. The insects are only a persistent problem during summer months which usually means hot temperatures around 100 F. The purpose of this work is to design an experimental set up that can accurately control the temperature of an airfoil leading edge and the speed of the insect used. The insects chosen for this experiment were live flightless fruit flies (Drosophila melanogaster). Consideration for the labs previous studies were used so the airfoil of choice was NACA 0038R with a cylindrical leading edge to use as a control against future heated test. The goal of this project is to create a set-up to optimize the current insect phobic coating to make it so that NLF can be used which will save fuel consumption during cruising of flights.