Abstract
Two acoustic levitation test facilities have been developed for cloud physics experimentation. These facilities utilize acoustic standing wave energy to suspend both solid and liquid objects in a contact-free environment. In the still-air facility, the air in the test section is essentially motionless, whereas in the ventilated facility, a small vertical wind tunnel creates a steady flow through the test section. Temperature control is available in both facilities, and relative humidity can be adjusted in the still-air facility. It was observed that liquid samples deform, to first order, into shapes characteristic of freely failing raindrops when subjected to the acoustic standing wave. It was also determined that the presence of an acoustic field in the test section does not significantly affect molecular diffusion processes. Water-droplet freezing experiments were conducted in both facilities to demonstrate the capability to support samples during a change of phase.
