The Effect of Wing Mass and Wing Elevation Motion During Insect Forward Flight

Abstract

AbstractThis paper is concerned with the numerical simulation of the forward flight of a high Reynolds number flapping-wing flyer, modelled after the hummingbird hawkmoth (Macroglossum stellatarum). The numerical model integrated a Navier-Stokes solver with the Newtonian free-body dynamics of the model insect. The primary cyclic kinematics of wings were assumed to be sinusoidal for simplicity here, which comprises sweeping, elevating and twisting related wing actions. The free flight simulation is very computationally intensive due to the large mesh scale and the iterative solution for the FSI problem, so parallelization is essential in the numerical simulation. Two parallelization techniques are used in current simulation, i.e., open multi-processing (OpenMP) and graphics processing units (GPU) acceleration. The forward flight mainly consists of two stages, i.e., the body pitching down from the normal hovering posture and the following forward acceleration. During this process, the effect of the wing mass and the wing elevation motion is very important, which is investigated in detail. It is found that Oval-shaped wing elevating motion can help to generate large pitching down moment so that the flyer can quickly adjust its orientation for forward acceleration. Moreover, wing mass tends to magnify the effect and prohibits the growth of pitching down velocity, which is favourable aspect. The present study provides detailed information of the coupled dynamics of fluid and flyer in free flight condition, as well as offers a prospective approach that could complement existing experiments in a wider study of insect flight and maneuver.