Laboratory testing of insect contamination with application to laminar flow technologies, Part I: Variables affecting insect impact dynamics

The effectiveness of laminar flow technologies can be limited by insect contamination on aircraft leading edge surfaces. In order to effectively manufacture and evaluate anti-contamination coatings a comprehensive understanding of the dynamics of an insect impact event – how the insect ruptures and adheres to the surface – is necessary. Two test facilities (developed independently) were used to study insect impact dynamics; both capable of producing single and multiple insect impacts at speeds of up to 100 m/s. In Part I of this paper, the variables affecting insect impact dynamics are identified. It was found that the effect of angle of impact and impact speed significantly influence the insect residue patterns. Exposure to a constant airflow during the insect impact event imparts a shear force, resulting in an increase in the residue area and a decrease in the height measurements. The dominant factor influencing the rupture velocity (i.e. the lowest speed needed to fracture the exoskeleton) was found to be the orientation of the insect body relative to the surface upon impact. Insect impact dynamics were classed into four separate regimes: sticking, bouncing, spreading and splashing. In Part II of this paper, an evaluation of candidate anti-contamination coatings is presented and the variables affecting the effectiveness of these coatings, such as different insect types and sizes, are assessed.