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

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
expensive to simulate on Earth. Additionally, the fundamental basis of the Navier-Stokes equations
(Reynolds-averaged) tightly couples CFD to physics.
The ability to acquire the data from the time history of unsteady forces and vortex formation on
the wing is extremely important and has been demonstrated in this report. The Entomopter vehicle
design hinges on whether or not the wings can generate sufficient lift and have an acceptable
lift-to-drag ratio.
This section will address computations with the CFD codes WIND and FLUENT, as well as
codes from Metacomp Technologies, Inc., presented in chronological order. Three-dimensional
cases with blowing were simulated initially using WIND to determine if aerodynamic performance
can be enhanced by surface blowing. Cases showing the effect of blowing tangential to
the trailing edge surface are presented. Animations of the resulting flow fields show the effect of
blowing. A major part of the effort at the University of Missouri-Rolla (UMR) with FLUENT
has been to design the airfoil section and the 3D planform to mimic the aerodynamic attributes
of a typical insect wing. A cicada wing was analyzed for its aerodynamic parameters, such as
camber, thickness, planform, structural attributes, and role of the hind wing. Extensive literature
review was conducted on the aerodynamic aspects of insect flight and the current status of
insect-derived MAV design. A series of two-dimensional studies was conducted using FLUENT
to optimize airfoil section parameters, such as thickness and camber, and to establish leading
edge vortex (LEV) behavior. Reynolds number was varied by a factor of 10, and the resulting
flow fields have been analyzed. A small thickness, cambered three-dimensional wing was
designed for the work in progress on flapping wing simulations. Understanding low Reynolds
unsteady aerodynamics and controlling wing kinematics during the stroke cycle have been identified
as key topics for the continuing Entomopter CFD work.
3.3.1.2 Entomopter Wing CFD Analysis: WIND
Preliminary CFD calculations were conducted with WIND Version 3 Code [283], a product of
the NPARC Alliance, a partnership between NASA Glenn Research Center (GRC) and Arnold
Engineering Development Center (AEDC) dedicated to the establishment of a national, applications-oriented
flow-simulation capability. WIND solves the Reynolds-averaged Navier-Stokes
equations, along with supporting equation sets governing turbulent and chemically reactive
flows.
Calculations with WIND were completed early in the project to get some idea of the complexity
and physics associated with a sinusoidally oscillating airfoil with tangential blowing. Although
the sinusoidal flapping motion did not physically represent the actual motion of the Entomopter
wing, purely sinusoidal flapping runs were important in understanding basic vortex creation and
convection over the airfoil, which ultimately drives the aerodynamics and wing lift.
Both steady and unsteady computations with an oscillating inflow and blowing (mass ejection at
the wing tips) were completed to assess the code's ability to handle this very demanding flow
field, which includes a very low Mach number inflow, with sinusoidal oscillation to simulate
flapping motion, and mass ejection on the outer wing panels to simulate blowing. Blowing is
used to entrain lower energy boundary-layer air and reenergize it with higher energy air,
decreasing the tendency for the flow to separate and thereby increasing circulation. This, along
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Phase II Final Report