Acoustic absorption measurement for the determination of the volume viscosity of pure fluids / Messverfahren für die akustischen Absorption zur Bestimmung der Volumenviskosität reiner Fluide (original) (raw)
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Acoustic absorption measurement for the determination of the volume viscosity of pure fluids
2019
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.
An acoustic transmission sensor for the longitudinal viscosity of fluids
Sensors and Actuators A: Physical, 2013
Physical fluid parameters like viscosity, mass density and sound velocity can be determined utilizing ultrasonic sensors. We introduce the concept of a recently devised transmission based sensor utilizing pressure waves to determine the longitudinal viscosity, bulk viscosity, and second coefficient of viscosity of a sample fluid in a test chamber. A model is presented which allows determining these parameters from measurement values by means of a fit. The setup is particularly suited for liquids featuring higher viscosities for which measurement data are scarcely available to date. The setup can also be used to estimate the sound velocity in a simple manner from the phase of the transfer function.
Experimental Estimation of Acoustic Attenuation and Dispersion
2005 2nd International Conference on Electrical and Electronics Engineering, 2005
In the research of methods for evaluation and characterization of therapy ultrasound transducers that will be used in the hyperthermia applications, the measurement of some acoustic parameters is specially important. We have used a modified broadband through-transmission technique proposed by Ping He [1,3] for measuring acoustic dispersion and attenuation because it requires a minimum number of variables to be measured and eliminates the needs for measuring the speed of sound in the water and the trigger delays in data sampling. In addition it minimizes the uncertainty in determining the phase spectra. Unfortunately we have found some inconvenient aspects of this technique in our application.
Measurement of the sound velocity in fluids using the echo signals from scattering particles
Ultrasonics, 2012
With conventional methods the sound velocity c in fluids can be determined using the back wall echo. This paper proposes a novel technique, in which the signals reflected by scattering particles suspended in a fluid are analysed instead. The basic idea is that the particles generate the strongest echo signal when being located in the sound field maximum. Therefore the position of the echo signal maximum is a measure for the propagation time to the sound field maximum. Provided that calibration data or sound field simulations for the ultrasonic transducer are available, this propagation time suffices to determine both sound velocity and the location of the sound field maximum. The feasibility of the new approach is demonstrated by different kinds of experiments: (i) Measurements of the sound velocity c in four fluids covering the wide range between 1116 and 2740 m/s. The results show good agreement with values published elsewhere. (ii) Using the dependence of the sound velocity on temperature, it is possible to vary c over the comparatively small range between 1431 and 1555 m/s with increments of less than 10 m/s. The measured statistical variation of 1.4 m/s corresponds to a relative uncertainty not worse than 0.1%. (iii) The focus position, i.e. the distance of the maximum of the sound field from the transducer, was varied by time-shifted superposition of the receive signals belonging to the different elements of an annular array. The results indicate that the novel method is even capable of measuring profiles of the sound velocity along the ultrasonic beam non-invasively.
Bulk viscosity of water in acoustic modal analysis and experiment
EPJ Web of Conferences, 2018
Bulk viscosity is an important factor in the damping properties of fluid systems and exhibits frequency dependent behaviour. A comparison between modal analysis in ANSYS Acoustics, custom code and experimental data is presented in this paper. The measured system consists of closed ended water-filled steel pipes of different lengths. The influence of a pipe wall, flanges on both ends and longitudinal waves in the structural part were included in measurement evaluation. Therefore, the obtained values of sound speed and bulk viscosity are parameters of the fluid. A numerical simulation was carried out only using fluid volume in a range of bulk viscosity. Damping characteristics in this range were compared to measured values. The results show a significant influence of sound speed and subsequently, the use of sound speed value regressed from experimental data yields a better fit between the measurement and the computation.
Sound velocity measurements in fluids using echo signals from scattering particles
2012
A novel approach for measuring the speed of sound in fluids with scattering particles is presented. Potential fields of application for sound velocity measurements in fluids are process control, environmental measurement technology and medicine, where sound velocity can be used as an indicator of temperature, concentration or mass density. Similar to the pulsed Doppler application, the method also works non-invasively and uses the echo signals from scattering particles suspended in the fluid. The basic idea is that the ultrasonic time of flight to the focus position z depends on the speed of sound c in a well-defined way. The time of flight to the focus can be extracted from the echo signals, because the stray echo is strongest for the scattering particles being located in the sound focus and can thus be used to determine the speed of sound. Results are shown for different homogeneous fluids with sound velocities between 1116 m/s (ethanol, 50 °C) and 2740 m/s (eutectic GaInSn). Meas...
Reduction of systematic measurement deviation in acoustic absorption measurement systems
2020
Motivation One major issue in the realization of acoustic absorption measurement systems is the fact that the absorption caused by dissipative effects in the fluid, such as viscosity, is superimposed by other losses resulting from the sound propagation in the respective measurement system. Examples for these effects are the spreading of the acoustic signal caused by diffraction and unwanted transmission at acoustic reflectors or waveguide boundaries. Unwanted reflected signals from planar surfaces included in the measurement system for constructive reasons may also interfere with the measurement. In this contribution, we describe several measures, which aim to reduce systematic measurement deviation by decreasing or compensating the aforementioned effects.
Noninvasive Fluid Property Measurements Using Acoustic Methods
Journal of the Association for Laboratory Automation, 2006
T he properties of a fluid are normally determined using invasive methods. These methods may lead to possibly contaminating or consuming the sample. When only very small amounts of a valuable sample exist, noninvasive measurement methods are preferred. The properties of fluids can then be used to deduce additional properties based on known relationships. In one case, the surface tension of a fluid may be used to determine the concentration of a fluid. We describe a measurement technique involving excitation of the surface of the fluid and the measurement of its response. An acoustic wave is used to both excite and monitor the surface of the liquid. This technique is used to determine the concentration of DMSO and water in solution, and the result determines the amount of fluid needed to deliver an accurate amount of solute in solution. (JALA 2006;11:188-94)
Nondestructive Characterization of Materials VIII, 1998
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