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

1pPA15. Numerical investigations of modified Greenspan viscometers.

James B. Mehl

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

Phys. Dept., Univ. of Delaware, Newark, DE 19711-2570

Modified Greenspan viscometers are being studied with the objective of better understanding of inertial and dissipative duct-end effects for application to Greenspan viscometers. Greenspan viscometers are double Helmholtz resonators comprised of a circular duct coupling two concentric cylindrical chambers. Previous investigations [J. B. Mehl, J. Acoust. Soc. Am. 97, 3327 (1995)] of the acoustic fields and eigenfrequencies of viscometers with ducts terminating flush with the chamber ends have been extended to ducts which extend into the chambers a distance D. Numerically determined end effects are compared with analytic results for radiation from baffled and unbaffled open ducts. When D=0 the inertial end correction agrees well with the correction for a baffled open end; when D is greater than a few duct diameters it approaches the value for an unbaffled termination. In contrast, the resistance of the duct end (defined for the limiting case of a small viscous penetration length) is not sensitive to D. The numerical model permits easy investigation of the effects of rounding and chamfering corners. [Work supported by the Office of Naval Research.]