ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

1pPA14. Systematic measurements of duct end corrections in the Greenspan viscometer.

Keith A. Gillis

Michael R. Moldover

James B. Mehl

Natl. Inst. of Standards and Technol., Thermophys. Div., Gaithersburg, MD 20899

A Greenspan viscometer is a Helmholtz resonator that has been optimized for viscosity measurements in gases. It consists of two chambers connected by a duct. The model, design considerations, and performance of such a device have been described elsewhere [Gillis et al., ``Acoustic Greenspan viscometer for gases,'' submitted to Rev. Sci. Instrum.]. The model represented the effects of nonuniform flow near the ends of the duct as a complex acoustic impedance Z[inf end], based on the numerical calculations by Mehl [J. Acoust. Soc. Am. 97, 3327 (1995) and unpublished calculations]. In this work, the ``end corrections'' were measured in a Greenspan viscometer with interchangeable ducts and a detector located in each chamber. This new design enabled a series of viscosity measurements to be performed with the same chambers and transducers, and with three different duct lengths and two duct diameters. The consistency between the experiments and the model will be presented. [Work supported by the Office of Naval Research.]