Ross, B. B. | Search NASA

NASA NTRS1980

The influence of wall resonances on the levitation of objects in a single-axis acoustic processing chamber

Instabilities were observed in high temperature, single axis acoustic processing chambers. At certain temperatures, strong wall resonances were generated within the processing chamber itself and these transverse resonances were thought sufficient to disrupt the levitation well. These wall resonances are apparently not strong enough to cause instabilities in the levitation well.

Ross, B. B.↗

NASA NTRS1979

Some limitations on processing materials in acoustic levitation devices

The spot heating of samples, suspended in an acoustic field, was investigated to determine if the technique could be used to process materials. A single axis resonance device operating in air at 25 C with an rms pressure maximum of 160 to 170 db was used in the experiments. The heat flow from a hot object suspended in a levitation node is dominated by the effects of the field, with the heat loss approximately 20 times larger than that due to natural convection. The acoustic forces which suspend the body at a node also serve to eject the heated air. The coupling between the locally heated region around the body and the acoustic field results in instabilities in both the pressure wave and force field. The investigations indicated the extreme difficulties in developing a materials processing device based on acoustic/spot heating for use in a terrestrial environment.

Oran, W. A.↗

NASA NTRS1971

A numerical solution of the planar supersonic near-wake with its error analysis

Planar supersonic near wake flow field problem with variable viscosity and base injection, investigating boundary errors spatial decay rate

Cheng, S. I.↗