Two novel acoustic resonators have been developed, one for measuring the viscosity and a second for measuring the Prandtl number of gases. For viscosity measurements, we use a double Helmholtz resonator called the Greenspan viscometer. The Greenspan viscometer has a single, isolated, low-frequency mode that is fitted to determine the gas's viscous diffusivity to obtain either the absolute or the relative viscosity. For Prandtl number, we use a cylindrical resonator that has been modified by inserting an array of short, parallel plates or ducts half way between the ends. Once calibrated, the lower longitudinal modes of this resonator are fitted to determine the Prandtl number. Detailed acoustic models of both resonators have been developed and are necessary to realize the full precision and accuracy of these techniques. The transport properties of helium, argon, propane, and helium-xenon mixtures have been measured with these techniques.
16th ICA/135th ASA Meeting
June 20-26, 1998
International Congress on Acoustics
gas, measurements, Prandtl number, thermal conductivity, transport properties, viscosity