E15 Energy efficiency

Topic

The energy efficiency of this insect's flight—specifically the insect serving as the model for this case—incorporates three components of the total flight power: induced power (required to generate lift by accelerating a mass of air downward), parasitic power (associated with the drag on the insect's body as it moves forward), and profile power (associated with the viscous drag on the wings).

Conversely, Rankine-Froude actuator disk theory predicts that the insect's induced power rises sharply with the thrust it generates, making hovering particularly energetically costly for large insects.

There is an optimal speed at which the insect's total power—and thus its cost of transport—is minimized; this point arises from the intersection of induced power (which decreases as speed increases) and parasitic power (which increases as speed increases).

Typically, the insect operates near this optimal speed during sustained flight; it engages in hovering only when foraging for nectar—such as the bee used as a model in studies of optic flow balance—or when capturing prey. Consequently, this model—incorporating the three power components associated with the flight energy efficiency introduced at the outset—determines that the insect's final muscular efficiency limits the net mechanical power available from the metabolic energy (defined elsewhere in this framework as the difference between flight and basal metabolism); at the same time, this muscular efficiency reduces the metabolic cost—a cost also defined elsewhere in the framework—through the mechanical resonance of the wingbeat. The fact that the insect's final muscular efficiency is even higher means that the net mechanical power available for those three initial power components is, in turn, also greater, derived from that same metabolic energy.

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