Phase II Final Report - NASA's Institute for Advanced Concepts

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
by the flapping motion. This interaction is dependent on the Reynolds number. As the Reynolds
number increases, this lift-producing mechanism diminishes. Experiments have shown that flow
on an insect wing at Reynolds numbers greater than 10 6 there is a crisis of flow over the wing
caused by early boundary layer separation. As the Reynolds number decreases around 10 4 this
crisis is greatly reduced and the flow displays a smoother shape. At Reynolds numbers of 10 to
10 3 flow separation is absent. As the Reynolds number decreases, other lift-producing mechanisms
such as differential velocity and drag, and other boundary layer effects may come into
play. These Reynolds number effects are a main reason for the difference in the flight characteristics
between birds and insects. A diagram of this vortex generation is shown in Figure 1-1.
This vortex generation is not completely explained by present theory. However, it is believed
that it is caused by the separation of flow over the leading edge of the insect wing. A diagram of
the vortex formation is shown in Figure 1-2. [69, 110]]
Figure 1-1: Conventional Airfoil and Insect Wing Lift-Generation Mechanisms
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Phase II Final Report