National Institute of Standards & Technology, Acquisition & Assistance Div.,100 Bureau Drive Stop 3572, Bldg. 301, Rm B117, Gaithersburg, MD 20899-3572

A -- PREPARE TECHNICAL REPORTS SOL 53SBNB967091 DUE 091399 POC Patrick Staines, (301) 975-6335 WEB: NIST Contracts Homepage, http://www.nist.gov/admin/od/contract/contract.htm. E-MAIL: NIST Contracts Office, Contract@nist.gov. The National Institute of Standards and Technology (NIST) intends to negotiate on a sole source basis with James B. Mehl to provide services to prepare a series of technical reports. The following reports will be prepared: 1. Acoustic spectrum of the double Helmhotz resonator. The acoustic modes of a cavity resonator consisting of two concentric circular cylinders coupled by a concentric cylindrical duct will be calculated for a representative series of dimensional parameters. The frequency range will extend from the low "Greenspan viscometer" frequency to an upper frequency a factor of 3 above the lowest frequency of any of the component parts. The report will include numerical calculations and a discussion, based on analytic approximations, of the couplings between the component parts. 2. The effective mass of the fluid in a Greenspan viscometer. The translational momentum of a Greenspan viscometer will be evaluated numerically. The report will include a discussion of the relevance of the effective mass to experiments in which the Greenspan viscometer will be used with working fluids of densities comparable with water under ambient conditions. 3. The elastic deformation of a Greenspan viscometer. The elastic properties of a Greenspan viscometer and associated transducers will be evaluated for application to high density fluids, i.e. fluids with densities comparable with liquid water under ambient conditions. 4. Coupling of a Greenspan viscometer to external environment. The acoustic consequences, in particular the contribution to the inverse quality factor, of the coupling of the resonator body to the external environment through physical supports will be calculated. 5. Greenspan viscometer orifice design. The inertance and resistance parameters used to describe the duct end effects will be evaluated for representative orifice cross sections. The cross sections will include a sharp, right angle corner at the intersection of the duct wall and the duct end, a cross section in which the sharp corner is replaced with a 45-degree bevel, and cross section in which the sharp corner is replaced with a circular arc. The dependence of the inertance and resistance on the dimensions of each design will be calculated and tabulated. The effects of non-linear processes will be investigated by calculating the Reynolds number for each shape investigated. 6. Prandtl meter viscous entrance effects. The acoustic Prandtl meter consists of a honeycomb structure of hexagonal symmetry interposed in acoustic flow at the center of an acoustic resonator excited in the plane-wave modes. The honeycomb structure, or insert, strongly perturbs the odd-numbered modes due to viscous coupling, and the even-numbered modes through thermal coupling. The theoretical model of the experiment is based on an approximate treatment that does not include entrance effects nor the effects of the hexagonal channel shape. The entrance effects will be estimated using the model of parallel plates interposed in similar acoustic flow. Separate treatments of thestrong viscous and strong thermal coupling cases will be developed. The effects of the hexagonal channel will be modeled through calculations of the inertance and resistance per unit length of duct. 7. Mass diffusion in acoustic boundary layers. The consequences of mass diffusion in binary mixtures will be investigated. A review of classical work [Landau and Lifschitz, Fluid Mechanics (1982)] and recent thermoacoustic work [Swift and Spoor, preprint] will be written. The relevance of the effects to measurements with the Greenspan viscometer and Prandtl meter will be explored. 8. The effects of corrugated boundaries on mixture separation (Task 7) will be investigated through a series of numerical calculations. The period of performance will be from the date of award through September 30, 2000. James Mehl is an internationally recognized expert in the theory and measurement of properties of gas-filled acoustic cavities and has unique qualifications and expertise in this field. Professor Mehl's publications have appeared in peer-reviewed archival journals and review volumes . No solicitation will be issued. NIST anticipates awarding a firm fixed priced purchase order on or before 30 Sept 1999. If you should have any questions regarding this announcement please contact Patrick Staines at (301) 975-6335 or via email at patrick.staines@nist.gov. See Note 26. Posted 09/02/99 (W-SN375642). (0245)

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