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

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
The wing planform provided by GTRI to Metacomp Technologies for conversion to a CFD mesh
included a "blown flap" with a radius that was 4% of the maximum chord value as shown in
Figure 3-82. For the 0.6m winglet span, the max chord of the blown part is about 0.2m. This
leads to a 4% radius of about 8mm. Due to various constraints the blowing slot, tangential to the
blown flaps at the outer trailing edge and wing tip, was simulated to be about twice as large as it
would be were it to be implemented physically. This could result in a higher mass flow than necessary
to achieve a given degree of pneumatic control.
Figure 3-82: Dimensions Used for Entomopter Wing Mesh Generation
The Entomopter wing is designed to change its angle of attack at the top and bottom of the flapping
cycle based on the compliance of the wing material so that an optimum angle of attack (α)
is achieved without the use of actuators. The wing angle of attack changes throughout each wing
beat due to the absolute velocity change of each point along the wing as well as the flexing
motion of the wing itself. For the purposes of the Metacomp Technologies CFD wing design,
this change of wing α occurs rapidly near the top and bottom of the flap (rather than continuously).
Specifically, the angle of attack was chosen to be -8 o for the down beat, and +8 o for the
upbeat. Since most of the lift is expected to come from the wing beating and not the forward
flight, the wing makes its flip from –8 o to +8 o (and vice versa) in the first 10 o of wing flapping
after reaching the maximum excursion at the top/bottom of the flap. The rate of change in the
angle is modeled to be linear over this 10 o (going from –8 o to +8 o and vice versa) with the ±8 o
being held constant over the remainder of the flap.
Input parameters and boundary conditions used in this CFD analysis were:
1. Mars atmospheric parameters (STP within 3m of Mars equatorial surface)
2. Altitude: near surface (under 3m above mean planetary ground level)
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Phase II Final Report