Progress on Acoustic Measurements of the Bulk Viscosity of Near-Critical Xenon (BVX)

We plan to determine the bulk viscosity of xenon 10 times closer [in reduced temperature tau = (T-Tc)/Tc] to its liquid-vapor critical point than ever before. (Tc is the critical temperature.) To do so, we must measure the dispersion and attenuation of sound at frequencies 1/100 of those used previously. In general, sound attenuation has contributions from the bulk viscosity acting throughout the volume of the xenon as well as contributions from the thermal conductivity and the shear viscosity acting within thin thermoacoustic boundary layers at the interface between the xenon and the solid walls of the resonator. Thus, we can determine the bulk viscosity only when the boundary layer attenuation is small and well understood. We present a comparison of calculations and measurements of sound attenuation in the acoustic boundary layer of xenon near its liquid-vapor critical point

CCM.FF-K3.2011 Intercomparison for airspeed

The CCM.FF-K3.2011 comparison was organized for the purpose of determination of the degree of equivalence of the national standards for air speed over the range 0.5 m/s to 40 m/s. An ultrasonic anemometer and a Laser Doppler anemometer were used as transfer standards. Nine laboratories from three RMOs participated between July 2013 and July 2015 – EURAMET: PTB, Germany; LNE-CETIAT, France; INRIM, Italy; VSL, The Netherlands; E+E, Austria; SIM: NIST, measurements were provided at ambient conditions. All results of independent participants were used in the determination of the key comparison reference value (KCRV) and the uncertainty of the KCRV. The reference value was determined at each air speed separately following “procedure A” presented by M. G. Cox. The degree of equivalence with the KCRV was calculated for each air speed and laboratory. Almost all reported results were consistent with the KCRV