Effects of wing–body interaction on hawk moth aerodynamics and energetics at various flight velocities

Abstract

Although the aerodynamics and energetics associated with single or paired flapping wings of insects have attracted significant attention, the aerodynamic interaction between the flapping wings and the flying body as a function of flight velocity remains an open question. Here, we present a computational fluid dynamic (CFD) study of hawk moth aerodynamics and energetics for hovering and forward flights of five different velocities. We build up a high-fidelity CFD wing–body (WB) model based on the realistic morphology and the WB kinematics of hawk moth Manduca sexta, which enables trimmed flapping flights based on a genetic algorithm embedded within a CFD-driven model. The effects of WB interactions on velocity-dependent aerodynamic performance are examined with WB, wing–wing, and body-only models in terms of leading-edge-vortex- and body-vortex-based mechanisms and their correlations with the production of aerodynamic forces and power consumption. While leading-edge-vortices are a convergent mechanism responsible for creating most of the aerodynamic force, the body-vortices created by WB interactions can augment the vertical force at all flight velocities, producing a 10% increase in fast flights. The time-averaged body-mass-specific mechanical power produces a J-shaped curve, which lowers power costs in intermediate- and high-velocity flights and saves energy from the WB interaction. An extensive investigation into aerodynamics and power consumption shows that high aspect-ratio wings increase wing- and body-based vertical forces, realistic wing-to-body mass ratios lead to low power costs, and slightly lower reduced frequency optimizes the aerodynamic performance. These results may help us to guide the design of future biomimetic flapping micro-aerial vehicles.