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

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
Figures 3-96 through 3-98 show the streamwise velocity contours. The z = -0.5m station shows
a marked difference from the unblown case. The blowing and the resulting Coanda effect have
resulted in the absence of flow separation on the top wing. This is the desired effect.
Note that in Figure 3-98, the trailing edge blowing at this station turns the flow down as desired
(perhaps 30°), however downward turning of 90 degrees is possible, producing a corresponding
increase in lift (in fact, wind tunnel tests have demonstrated that the local flow can be turned
180° using blown surfaces under correct circumstances). Within the time and funding allocated
to the CFD analyses performed on this NIAC Phase II study, it was not possible to identify an
optimal point in the design space where slot velocities and blown flap geometries would result in
optimum lift while the airfoil is being blown under Mars atmospheric conditions. The CFD
results shown demonstrate that increases in lift can be attained for the Entomopter wing on
Mars, but by no means indicate the maximum potential to be gained in doing so. For the design
point chosen (14 m/s forward flight and 6 m/s wing flapping over a 150° angle) a 100 m/s blowing
velocity yields forces on the order of 0.08125 Newtons with blowing whereas the unblown
wing only exhibits 0.046875 Newtons according to this single point CFD analysis (as shown in
Figures 3-90 and 3-95). Empirical wind tunnel data have shown analogous test set ups to produce
improvements in the range of 5 to 10 times this. [80, 82]
It is clear that the point in the design space is not optimum and while the present CFD model can
to be refined, the choice of better operating parameters is also necessary. This parametric analysis
will be conducted with the help of the analytical formulations developed during this study to
define the “sweet spots” for operation within the overall design space. This work (for the
unsteady blown flapping case) is being carried out as a Ph.D. research topic and will be further
pursued in follow-on research efforts.
Figure 3-96: U Velocity Contours on Symmetry Plane
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Phase II Final Report