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

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
The flow conditions used in the WIND simulations represented the Mars environment. These
conditions are shown in the list above. Qualitative results from these simulations can be seen in
Figures 3-30 through 3-35. Figure 3-30 shows the complexity of the flowfield and dynamic stall
vortex using massless particles released ahead of the wing. Figure 3-32 shows the outline of the
wing (black lines) with a Mach number cut and velocity vectors depicted near the wing tip. A
dynamic stall vortex and flow ejection off the trailing edge can be seen. Figure 3-33 shows the
dynamic stall vortex using streamlines. Figures 3-34 and 3-35 show the airfoil surface and LEV
development. Animation of time-dependent calculations showed the familiar repeated shedding
of dynamic stall vortices from the leading edge across the airfoil. This interaction of vortices
with the upper wing surface at this Reynolds number results in higher lift coefficients over the
case without oscillation (a static airfoil such as on a fixed wing airplane).
Quantitative results were also obtained, as shown in Figures 3-36 and 3-37. Figure 3-36 shows
the drag coefficient vs. time with blowing and oscillation. Figure 3-37 shows the lift coefficient
vs. time with blowing and oscillation. Similar lift and drag results were found for the case without
blowing. It is expected that blowing should increase circulation above and beyond the contributions
to oscillation alone.
However, in all figures except Figure 3-31, the blowing was ejected tangential to the top wing
surface (which is essentially horizontal). However, blowing horizontally off of the flat trailing
edge just acts as a jet of air, and does not add to circulation of the airfoil. Thus, the WIND flapping
(or oscillating) results show similar lift and drag for the case with and without blowing
when a zero-degree jet angle is used. This combination of blowing and flapping gave a maximum
lift coefficient of 4 and maximum drag coefficient of 0.85 at a total pressure ratio of 1.27.
Figure 3-38 shows the pressure contour field for the case with blowing (left) and no blowing
(right). As a side study, a few calculations were completed with mass ejection at a 30 deg angle
down (Figure 3-31) from the bottom rear of the airfoil (jet flap), in hopes that it would help
induce circulation over the top of the airfoil. It turned out it did not, agreeing with the limited lift
augementation benefit of the jet flap concept seen in literature. It should be mentioned that the
high lift augmentation characteristics of blowing over a curved trailing edge [81] which we envision
for use on this vehicle have not yet been investigated here.
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Phase II Final Report