Acoustic absorption measurement for the determination of the volume viscosity of pure fluids / Messverfahren für die akustischen Absorption zur Bestimmung der Volumenviskosität reiner Fluide

Abstract

A realistic description of fluid mechanical and acoustic processes requires the volume viscosity of the medium to be known. This work describes how the volume viscosity of pure fluids can be determined by measuring acoustic absorption with the pulse-echo method. The challenge in realizing such a measurement method lies in the separation of the different dissipative effects that superimpose on absorption. Diffraction effects ultimately cause a dissipation of acoustic energy and acoustic reflector surfaces have a small, but finite transmission coefficient. Further, influences of the transducer (in particular its frequency response), as well as the system’s electrical components have to be taken into account. In contrast to the classical approach relying on the amplitude ratio, the absorption is determined by the moments of the amplitude spectrum. The measurement system applied is originally designed for precision measurements of the sound velocity by means of the propagation time difference of two acoustic signals.

Bulk viscosity of liquid noble gases

“…While the uncertainty of most recent thermodynamic data are well established to range from Δρ/ρ = 0.005 to Δμs/μs = 0.3 depending on substance and state, the attenuation coefficient α λ has been determined by single measurements at the respective state point, and thus, only its absolute maximum errors Δα λ have been estimated. Moreover, it is not assured that systematic measurement errors in the literature data, specifically diffraction effects, 128 were properly accounted for. Consequently, the reduced bulk viscosity's uncertainty Δμ b was determined to be linearly affected 129 by its various contributions Δα λ , Δc, Δμs, Δγ, Δcv, Δcp, After selecting and evaluating the experimental data, a decline of the bulk viscosity along each isotherm, i.e., from saturation line toward higher density, can qualitatively be inferred.…”

Estimation of Tissue Attenuation from Ultrasonic B-Mode Images—Spectral-Log-Difference and Method-of-Moments Algorithms Compared

“…Another method for estimating the attenuation coefficient as discussed in the literature [10,11] is again based on the power spectral densities S p ( f ) and S d ( f ) averaged over two spatially limited regions of interest (cf. Figure 5) from l to r laterally and from c • dt • n dm /2 to c • dt • n d1 /2 for the distal, and from c • dt • n pm /2 to c • dt • n pm /2 for the proximal window, respectively, radially.…”

“…Given that the speed of sound, c ≈ 1540 m/s, on the order of N = 10 4 samples are acquired for each scan line for a typical ≈ 5 cm depth range. In our work, we compare results obtained by the spectral-log-difference (SLD) method [3,9,22] and the statistical moments (MoM) based approach [10,11] for three numerical phantoms.…”

“…Although there still does not exist a robust estimation method to determine spatially resolved attenuation coefficient, several authors have addressed that problem and developed a variety of methods both in the time as well as in the frequency domain [1][2][3]. We employ a sound field simulation software (k-Wave [8]) to generate B-mode scans of a numerically very well characterized volume and are thus able to compare the estimation results obtained for two techniques, the spectral-log-difference technique [9] and the method of moments [10,11]. Table 1.…”

Ultrasonic testing of the biomechanical properties of donation blood

“…We also considered testing the relative nonlinearity coefficient B/ A. This sensitive biomechanical property has long been utilized in ultrasonic imaging of blood and biomolecular imaging [26][27][28], as well as for quantitative non-destructive investigations [29]. The sequential variations of the three parameters are compared to their values at the beginning of the storage period, when the sample is fresh and ideal for transfusion and, therefore, can be regarded as the reference sample.…”