Dembelova T.S., Makarova D.N., Badmaev B.B. «Low-Frequency Shear Elasticity of the Homological Series of Normal Hydrocarbons» Acoustical Physics, 70, № 1, с. 35-38 (2024)

The low-frequency (74 kHz) shear elasticity of the homologous series of normal hydrocarbons (alkanes) is studied using acoustic resonance. The shear modulus and mechanical loss tangent are measured, and the relaxation frequency and effective viscosity are calculated. The dependences of these parameters on homologue viscosity are established. It is shown that the mechanical loss tangent of all studied liquids is less than 1, demonstrating that the relaxation frequency is below the experimental frequency.

Bai Yunshan, Liu Yuanxue, Gao Guangjian, Cui Dandan, Chen Han «Estimating the Azimuth of Acoustic Emission Source in Concrete Plate-Like Structures using a Non-Contact Sensor Unit» Acoustical Physics, 70, № 1, с. 130-142 (2024)

Location of damage sources is an important aspect of structural health monitoring research. Acoustic emission (AE) technology is broadly concerned due to its potential advantages in damage monitoring and source localization. However, the traditional positioning method is based on the arrival of P wave, and the non-uniformity of concrete materials is not considered, resulting in poor accuracy at large distances. This paper describes a non-contact AE localization method using leaky Rayleigh waves via a new air-coupled MEMS microphones array unit. Compared with traditional contact detection, this method is convenient for rapid setup and monitoring in a wider range. The feasibility of the non-contact AE localization method was verified by numerical simulation and experiments. Azimuth (direction of arrival) of AE source is a key source parameter for damage location. The research shows that this method can determine the azimuth of AE source at different positions, the results are close to the actual coordinates. Non-contact monitoring method proposed in this paper is the basis for further research on the failure prediction of concrete plate-like structures such as tunnel lining and bridge deck.

Bakushinsky B., Leonov A.S. «Modeling the Solution of the Acoustic Inverse Problem of Scattering for a Three-Dimensional Nonstationary Medium» Acoustical Physics, 70, № 1, с. 153-164 (2024)

The inverse problem of acoustic sounding of a three-dimensional nonstationary medium is considered, based on the Cauchy problem for the wave equation with a sound speed coefficient depending on the spatial coordinates and time. The data in the inverse problem are measurements of time-dependent acoustic pressure in some spatial domain. Using these data, it is necessary to determine the positions of local acoustic inhomogeneities (spatial sound speed distributions), which change over time. A special idealized sounding model is used, in which, in particular, it is assumed that the spatial sound speed distribution changes little in the interval between source time pulses. With such a model, the inverse problem is reduced to solving three-dimensional Fredholm linear integral equations for each sounding time interval. Using these solutions, the spatial sound speed distributions are calculated in each sounding time interval. When a special (plane-layer) geometric scheme for the location of the observation and sounding domains is included in the sounding scheme, the inverse problem can be reduced to solving systems of one-dimensional linear Fredholm integral equations, which are solved by well-known methods for regularizing ill-posed problems. This makes it possible to solve the three-dimensional inverse problem of determining the nonstationary sound speed distribution in the sounded medium on a personal computer of average performance for fairly detailed spatial grids in a few minutes. The efficiency of the corresponding algorithm for solving a three-dimensional nonstationary inverse sounding problem in the case of moving local acoustic inhomogeneities is illustrated by solving a number of model problems.

Raza M., Ahsan M., Wee M.F.M.R., Baqir M.A. «Investigation of Open Cloaking of Acoustic Fields via Transformation Optics» Acoustical Physics, 70, № 1, с. 76-81 (2024)

The conventional cloak has been studied in vast space while the open cloaking is explored in a few articles and there is a dire need for further investigations in this field. The open cloaks provide a way to exchange information data from the cloaked region to outside and vice versa. In this work, we have investigated the open cloaking phenomenon in acoustic fields at an audible frequency. This study will be helpful in developing a Multiphysics open cloaking platform and cloaked will enable to transfer or prohibition of the exchange of material from one region to another.

Bashkatov V.V., Ostrikov N.N. «Influence of the Nonlinear Operating Mode of Acoustic Liners at High Sound Pressure Levels on Sound Wave Propagation in a Cylindrical Duct with a Flow» Acoustical Physics, 70, № 1, с. 9-20 (2024)

The problem of sound propagation in a cylindrical duct with a uniform flow is considered with nonlinear impedance boundary conditions resulting from the dependence of the impedance of acoustic liners on the sound pressure level. An iterative procedure for solving this problem has been constructed, in which sound propagation is described by an asymptotic solution to the problem of the propagation of sound modes in a cylindrical duct with a uniform flow with a smoothly non-uniform impedance of the walls in the axial direction, and the nonlinear mode of operation of the liners is based on a semiempirical model of a two-layer acoustic liners. It is shown that the constructed iterative algorithm converges within the limits of applicability of the asymptotic solution and diverges beyond them. It is shown that, for the parameters with which the calculations were carried out, the nonlinear effect of the liners operation leads to an increase in sound attenuation compared to a linear solution of a similar problem, and this effect is when sound propagates along rather than against the flow.

Anosov A., Granovsky N.V., Belyaev R.V., Erofeev A.V., Sanin A.G., Mansfeld A.D. «Correlation Measurements of Thermal Acoustic Radiation Using a Sensor Array» Acoustical Physics, 70, № 1, с. 21-28 (2024)

An array consisting of three sensors was used for correlation measurements of thermal acoustic radiation. For the first time, all cross-correlation functions were obtained for each pair of sensors. The measurements were carried out at two positions of the source (a heated narrow Teflon cylinder), the distance between which was equal to half the spatial period of the cross-correlation function of adjacent sensors. The measured correlation functions were in antiphase, which corresponds to the calculated correlation functions of thermal acoustic radiation. To pass from correlation functions to temperature distribution, spatial cross-correlation functions for adjacent and the outermost sensors in the array are summed. The correlation methodology makes it possible to significantly increase the spatial resolution of the method.

Mansfeld D., Belyaev R.V., Volkov G.P., Kuzmin A.A., Sanin A.G., Shaikin A.A. «Monitoring the Internal Temperature of Active Elements of High-Power Lasers Using Ultrasonic Probing» Acoustical Physics, 70, № 1, с. 68-75 (2024)

Monitoring the internal temperature of active elements (AE) of high-power lasers is necessary for their safe operation. The article describes a method and device for monitoring the internal temperature of the AE of lasers. The measurements utilize pulsed ultrasonic (US) probing and the temperature dependence of the sound speed in the AE material. A change in the sound speed leads to a change in the phase of the ultrasonic signal passing through the object, which is recorded by the described device. The results of monitoring the AE temperature using ultrasonic probing during operation of a laser device are presented.

Fraunie P., Aldebert C., Devenon J.L., Bourras D., Sentchev A., Shrira V. «3D investigation of the turbulent marine Ekman layer» 9-я Международная конференция – школа молодых ученых «Волны и вихри в сложных средах». Москва, 05–07 декабря 2018 г., с. 9-10 (2018)

Bychkov P., Faranosov G.A. «Hot-Wire-Based Estimation of Pressure Fluctuations in the Near Field of a Jet in the Presence of a Coflow» Acoustical Physics, 70, № 1, с. 116-129 (2024)

It is shown that the velocity fluctuation spectra measured using a hot wire in the potential flow region of the near field of a turbulent jet with a coflow can be converted into pressure fluctuation spectra. The proposed conversion method is based on the fact that the structure of instability waves, which make a decisive contribution to jet near-field fluctuations, resembles homogeneous one-dimensional waves, which makes it possible to locally link pressure fluctuations and the fluctuations of the streamwise velocity component measured by a hot wire.