Acoustic Action Research Articles

Strong expansion–contraction of a cavity in a fluid under acoustic action

The simplest model of the strong expansion–contraction of a spherical evacuated cavity in an unbounded ideal incompressible fluid under acoustic action is constructed. It is assumed that the cavity is formed at the instant of maximum dilatation of the fluid as the result of the breakdown in its continuity by elementary particles, and the amplitude of the induced acoustic oscillations exceed the mean pressure in the fluid by an order of magnitude or more. The trajectory of the motion of the interface is divided into three stages, in each of which it is assumed that there is a certain constant value of the pressure. This enables an approximate analytical solution of the problem to be obtained. It is shown that there is an agreement with the numerical solution of the initial problem that is sufficient for qualitative estimates. The solution obtained enables a parametric analysis of the expansion–contraction processes of a cavity to be carried out and enables the volume of calculations in the numerical modelling to be reduced when taking account of additional factors.

Seismoacoustic emission of an oil-producing bed

Results are presented from a study of seismoacoustic emission appearing in an oil-saturated porous geological medium under the acoustic force action in a borehole. It is shown that dynamic nonlinear processes in the producing bed are activated under the internal elastic action on the stratum, changing the energy state of the medium, and this change can be seen as a change in the acoustic emission pattern. The correlation between the high-frequency part of the acoustic emission spectrum and the low-frequency one is found, indicating the development of this process in space at different scale levels.

Modeling of the dynamics of microbubble contrast agents in ultrasonic medicine: Survey

The survey is devoted to a new field of bubble dynamics that studies the behavior of ultrasound contrast agents. This name denotes man-made encapsulated microbubbles applied in diagnostic and therapeutic ultrasonic medicine to enhance the quality of ultrasonic images and to deliver drugs to target sites in the human body. The survey analyzes theoretical models that are currently applied for the description of the bubble shell, the interaction of bubbles with blood vessel walls, and the acoustical action of bubbles on the cell membrane.

The evolution of instabilities in gas microjets under acoustic action

The results of an experimental investigation of the effect of external acoustic perturbations on the stability of millimeter- and submillimeter-scale gas jets flowing out into the atmosphere are presented. Data on flow visualization by the shadow method and the instantaneous velocity fields of the flow by the PIV method are obtained. The sound effect in the jet is shown to lead to the asymmetric mode of instability. The growth of this mode downstream leads to flow bifurcation. Frequency characteristics of the effect for jets of different geometries and jets of different gases are compared.

An Action–Sound Approach to Teaching Interactive Music

The conceptual starting point for an ‘action–sound approach’ to teaching music technology is the acknowledgment of the couplings that exist in acoustic instruments between sounding objects, sound-producing actions and the resultant sounds themselves. Digital music technologies, on the other hand, are not limited to such natural couplings, but allow for arbitrary new relationships to be created between objects, actions and sounds. The endless possibilities of such virtual action–sound relationships can be exciting and creatively inspiring, but they can also lead to frustration among performers and confusion for audiences. This paper presents the theoretical foundations for an action–sound approach to electronic instrument design and discusses the ways in which this approach has shaped the undergraduate course titled ‘Interactive Music’ at the University of Oslo. In this course, students start out by exploring various types of acoustic action–sound couplings before moving on to designing, building, performing and evaluating both analogue and digital electronic instruments from an action–sound perspective.

Use of Pulsed Neutron Reagent Control in Acoustic Action on Oil Strata

Use of Pulsed Neutron Reagent Control in Acoustic Action on Oil Strata

Requirements on borehole radiators based on analytical estimation of radiated acoustic fields

Acoustic action on a productive stratum is one method for intensification of hydrocarbon mining. The physical mechanisms of acoustic action can be divided into two main groups: force and energy. The effect of any mechanism is associated with the structure and characteristics of the acoustic fields created by the radiation sources in the borehole. Therefore, the force and energy characteristics of the acoustic fields in the vicinity of a borehole are of high importance. These characteristics make it possible to estimate the prospects of applying the acoustic action under different conditions. The analytical estimates of the force and energy characteristics of the acoustic fields in the vicinity of a borehole are presented, and the requirements imposed on new-generation of borehole radiators are formulated on this basis, the use of which would help to more effectively develop deposits of highly viscous oils and residual gas condensates.

Detection of the external acoustic action upon an optical fiber using the interferometer of scattered radiation with the aid of the phase diversity method

The interferometer of scattered radiation is employed for the detection of the external acoustic action upon an optical fiber. A method for the demodulation of the scattered field using the phase diversity procedure is proposed. The possibility of the fading regions in the demodulated signal is demonstrated, the reasons for such an effect are analyzed, and the methods for its elimination are proposed.

Influence of the initial conditions at nozzle exit and acoustical action on the structure and stability of a plane jet

Victor V. Kozlov, Genrich R. Grek*, Yury A. Litvinenko, Grigory V. Kozlov, & Maria V. Litvinenko Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch of the Russian Academy of Sciences 4/5, Institutskaya str., Novosibirsk, 630090 Novosibirsk Region, Russia *Corresponding author: Genrich R. Grek, E-mail: grek@itam.nsc.ru The results of experimental investigations of the influence of the initial conditions at the nozzle exit and acoustical action on the structure of a plane jet, the characteristics of its evolution and stability are presented in this work. Peculiarities of the development of laminar and turbulent plane jets are shown for the same Reynolds number. Patterns of smoke visualization of the jet upon variation of the initial conditions of jet formation and acoustical action, and during the interaction of streaky structures with vortices of the laminar plane jet vortex street are discussed. Laminar and turbulent jets at the exit of a two-dimensional Hagen–Poiseuille channel are found to experience longitudinal sinusoidal oscillatory motion considered as a whole. Peculiarities of evolution of both laminar and turbulent jets under acoustical action are revealed. It is found that the generated symmetrical mode of instability of a laminar plane jet is suppressed by the asymmetrical mode of instability. The interaction of the streaky structures, generated on one side of a plane nozzle, with the vortices of a laminar plane jet with a parabolic mean velocity profile is shown to lead to the generation of Λor Ωlike vortices on both the left and right vortices of the vortex street. The results of the investigations are valid for jet flows with small Reynolds numbers.

Acoustic control of instability waves in a turbulent jet

The possibility of acoustic control of instability waves formed in the mixing layer of a jet is experimentally investigated. The feasibility of suppressing a hydrodynamic instability wave in a subsonic turbulent jet by an external acoustic action is demonstrated. This result can be used in designing active control systems for jet noise suppression.

Influence of magnetic and acoustic treatment of superplasticizer solutions on the properties of portland cement concretes

We have investigated the influence of the regimes of high-frequency magnetic-impulse and acoustic action on the physicochemical properties of water solutions of polycarboxylate superplasticizers and technological indices of fine concretes plasticized by them. The dependences of technological properties of concretes on the concentration of water solutions of the superplasticizers, the content of impurity ions in the water used for dilution, and the conditions of acousto-radiowave treatment have been determined. The regimes of activation of superplasticizer solutions, which permit increasing the mobility and keeping quality of concrete and solution mixes tempered with water and the density and strength of fine concretes formed from them, have been established.

On the interrelation between relaxation and hydrodynamic phenomena in nematic liquid crystals

The theoretical prediction of the interrelation between the relaxation processes and hydrodynamic phenomena observed in nematic liquid crystals (NLCs) under binary acoustic action at MHz frequencies is experimentally substantiated. The existence of a new (relaxation) mechanism of streaming generation in thin layers of the mesophase is proven by the results of measurements of the velocity of steady-state acoustic streaming in the NLC in a planar capillary with homeotropic boundary conditions induced by the simultaneous action of coherent compressional and shear waves. A model that takes into account not only the classical convective contribution to the streaming formation but also the nonlinear relaxation one is tested for the first time. It is shown that only this model describes the aforementioned phenomenon consistently with the experimental data.

Study of reaction of a viscous oil structure on actions by a physical field

The regularities of reaction of the viscous bitumen (maltha) structure when affected by modulated and impulse electromagnetic and acoustic fields via recording of infrared emission spectra are studied. It has been found that characteristic reactions of viscous oil clusters and links between them are located in the THz range for electromagnetic waves and in the MHz range for acoustic actions, which are revealed in absorption and emission spectra. The reaction of the rest (non-THz) part of the infrared spectrum is described on the basis of the physical-mathematical model of the process of a photon-phonon soliton, which causes decrease of emission IR spectrum intensity after microwave action due to fixation of the electromagnetic field by a soliton. The obtained results, which establish selectability of the maltha specimen reaction on spectral composition of the affected radiation, are important for increasing the efficiency of ultrasonic and electromagnetic microwave actions on the productive stratum during application of secondary methods for oil deposit exploration.

Influence of the methods of energy action on deflagration-to-detonation transition

The results of experimental gas-detonation investigations carried out in the past decade at the Department of Physical Gasdynamics of the Joint Institute of High Temperatures of the Russian Academy of Sciences (JIHT RAS) in connection with the problems of creation of a pulse detonation engine have been presented. Consideration has been given to the influence of the shape of injectors on the formation of detonation in a gas flow with separate feed of the fuel and the oxidant, the influence of acoustic action on the ignition region, reduction in the predetonation length in the flow of a mixture capable of detonation, and improvement in the efficiency of electric-discharge initiation of detonation by the self-magnetic and induced external magnetic field.

Vacuum ear plug.

A passive inexpensive hearing protection device (HPD) will be described that provides hearing protection, which is simple to use and comfortable over hours of use. Protection from impact sounds will be provided by creating a negative pressure between the plug tip and the eardrum (−100-mm H2O or −1 kPa). The negative pressure will be created by squeezing the peripheral plug end, evacuating a fixed amount of air from the canal. The aperture diameter is 0.010 in. In effect the pump plug will have a similar acoustical action on the eardrum as a normal stapedius muscle contraction, but without its limitations (too slow and fatigue). An external flexible bladder forms the end which is held in the fingers to be inserted into the ear canal. The vacuum mechanism consists of bulb on a polypropylene frame embedded in a closed cell urethane flanged housing. With a negative pressure of −2 kPa the transmission loss is 20–25 dB. It is estimated that a negative pressure of −1 kPa would result in a transmission loss of about 15 dB. The vacuum effect is maximal in the low frequencies which will also attenuate body conducted sounds by reducing ossicular inertial.

Film lamination method and lamination-apparatus

In a film lamination method of the present invention, sound waves with a predetermined frequency are applied to at least one of a substrate or a film disposed on the substrate. Thus, by means of an acoustic vibration energy action, the adhesion of the film to the substrate and the quality of covering irregularities can be sufficiently enhanced and the embedding quality of the film to the irregular portions of the substrate can be achieved to a high standard.

Advances in acoustics of liquid crystals

Advances in the fundamental problem of the orientation transition in liquid crystals produced by acoustical action are considered. The theoretical models to describe a variety of liquid crystals orientation transitions in acoustic fields for the homeotropically and planar oriented layers which were developed in the framework of the Leslie-Ericksen hydrodynamics and the new methodology based on the ideas of non-equilibrium thermodynamics and nonlinear hydrodynamics are discussed and are substantiated experimentally. The orientation phenomena in liquid crystals were classified and the physical factors defining a kind of transition (threshold or non-threshold type) and a choice of approach correct to describe adequately the experimental data on a new molecular arrangement induced by acoustical action were established. Among them a macrostructure type of liquid crystals layer, a layer thickness-viscous wavelength in liquid crystal ratio, an angle between the medium optical axe (the liquid crystal director) and the line of acoustical wave propagation, a sound intensity, a type of acoustical boundary conditions at the layer edges. The modern ideas on the distortion peculiarities of liquid crystals above a certain threshold of the structure instability under non-stationary dynamic action on the liquid crystal layer of sound-induced oscillating flows for a wide frequency band were considered.

Influence of initial conditions at the nozzle exit on the structure of round jet

Experimental data concerning the influence of initial conditions at the nozzle exit on the structure and development characteristics of round jets are reported. Features in the development of laminar and turbulent round jets emanating from variously elongated nozzles at identical Reynolds numbers are revealed. Smoke visualization pictures obtained for jets formed under different initial conditions (with different distributions of mean and pulsating flow velocities at the nozzle exit) are discussed. It is shown possible to make the zone of laminar flow in the jet stream more extended, and to delay the jet turbulization process in space, by making the flow-velocity profile more parabolic at the exit of elongated nozzle. Features in the development of vortical structures in a jet under an acoustic action are identified. It is shown that, for a turbulent round jet to be produced right at the nozzle exit, the nozzle length must be increased in excess of a certain value so that to provide for spatial growth of turbulent boundary layer thickness, finally ending in the formation of a fully turbulent flow velocity profile across the channel.

Manifestation of the stochastic resonance in submerged jets under an acoustic action

A phenomenon that is similar to the well-known stochastic resonance in nonlinear oscillators but is caused by the turbulence in a circular submerged jet under a harmonic acoustic action, rather than by noise, is considered. It is shown that, at a fixed distance from the nozzle, a variation of the initial turbulence level leads to a non-monotonic variation of the wave amplitude at the frequency of the acoustic action, namely, to the appearance of an amplitude maximum at a certain level of the initial turbulence. The qualitative explanation of the phenomenon consists in that the initial turbulence acts on the system in a way similar to that of external noise: it changes the effective parameters of the system and, in particular, shifts the spectral maxima, which is equivalent to a change in a certain “eigenfrequency.” Such a change in the effective parameters of the jet leads to a phenomenon similar to the stochastic resonance.

Mechanoelectrical transformations in quartz and quartz-bearing rocks under acoustic action

The data are reported for investigation into a frequency spectrum of an electromagnetic signal recorded in artificial crystal quartz and natural quartzite subject to a piezoacoustic action. Variations in the amplitude and duration of an exciting acoustic signal, as well as in the distance between a device, which receives the electromagnetic signal, and an emitting surface change the amplitude-frequency characteristics of the electromagnetic signals.