of Acoustic Shaping in Microgravity
The phenomenon of acoustic levitation has been demonstrated in several
applications. Intense sound fields created inside confined spaces exert
forces which can move small particles. The particles move to stable locations
with the least potential. The stable locations of the particles constitute
a balance between gravity, drag, surface forces, and acoustic pressure.
As an example, we may consider particles being moved using beat patterns
of sound waves, and induced to deposit along surfaces which join nodes
of the acoustic field. In a microgravity environment, this offers tremendous
potential for intricate fabrication technology. With the dominant
gravitational force removed, fine control can be exerted on the acoustic
field and the resulting movement and deposition patterns of the particles.
The particles can be solid or liquid. Thus, for example, we can induce
resins to harden along carefully-specified, intricate surfaces inside a
structure, with no need for access or machining.
Sound propagation is described by the wave equation,and the spatial geometry
of standing wave patterns formed by multiple waves is described by the
Helmholtz equation. Solution techniques are well-known for these equations,
and solution surfaces can be determined and tailored to obtain desired
surface shapes. From these solutions, the fluid velocity and pressure field
can also be determined. Particle mechanics in this field can also be computed.
This poses some uncertainties, especially in the microgravity environment,
which requires experimental validation. The data recovered from our flight-tests
abroad NASA's KC-135 will enable us to remove such unknowns and advance
the theory of acoustic levitation to acousticmanufacturing.
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L.D., Lifshitz, E.M., "Fluid Mechanics".Course on Theoretical Physics,
Volume 6, Pergamon Press, 1987, p. 305-307.
S.S., Sercovich,A.H., Komerath, N.M., "Acoustic Shaping in Microgravity:
Higher Order SurfaceShapes", AIAA Paper 99-0954, 37th Aerospace Sciences
Meeting & Exhibit,Reno, NV, January 1999.