Evaluation Using Dynamically Scaled Experiment of Dipteran Passive Pitching Motion Caused by Fluid-Structure Interaction

Abstract

In this study, we evaluated the dipteran passive pitching motions caused by the fluid-structure interaction using the dynamically scaled experiments. Since the model wing and the surrounding fluid interact with each other, the dynamic similarity between the model and the actual dipteran flights was measured using not only the Reynolds and Strouhal numbers but also the mass and Cauchy numbers. Using these four numbers, the data of the flapping flights of Tipula obsolete, Tipula paludosa, Eristalis tenax, Calliphora vicina were dynamically scaled and applied to the model wing flights. In all tested insect flights the characteristic pitching motions were well simulated, i.e. the model wing maintained the high angle of attack in the middle of each half stroke and rotated during the stroke reversals. The simulated pitch amplitudes were equivalent to those of observations in the actual insect flights and the generated lift was sufficient to support the insect weight. As a consequence the dipteran pitching motion is fundamentally caused by the fluid-structure interaction.