Influence Of Acoustic Field Research Articles

A Model for Shelled Micro-Bubble in Geometric Confinement under Acoustics Field

A theoretical model to predict the dynamics of a shelled micro-bubble driven by acoustic field in a tubular geometric confinement is proposed in the present study. The model is derived from first principle and may not be considered as a variant of Rayleigh-Plesset solution. A semi-analytical model is derived in the form of an ordinary differential equation connecting all parameters involved. Results obtained are in agreement with the available experimental data. The model is further linearized to obtain expression for the forced resonant frequency, which is shown to depend on geometric parameter of confinement as D/ where D and L are the tube diameter and length, respectively. Further, linear viscous damping coefficient is also studied and is found that an overdamped or an underdamped state exist base on shelled micro-bubble size and parameters of geometric confinement (L and D). The state of damping clearly indicate when the shelled micro-bubble in confinement would respond linearly or non-linearly under the influence of acoustic field‎.

The Influence of Acoustic Field Induced by HRT on Oscillation Behavior of a Single Droplet

This paper presents an experimental and theoretical study on the effects of an acoustic field induced by Hartmann Resonance Tube (HRT) on droplet deformation behavior. The characteristics of the acoustic field generated by HRT are investigated. Results show that the acoustic frequency decreases with the increase of the resonator length, the sound pressure level (SPL) increases with the increase of nozzle pressure ratio (NPR), and it is also noted that increasing resonator length can cause SPL to decrease, which has rarely been reported in published literature. Further theoretical analysis reveals that the resonance frequency of a droplet has several modes, and when the acoustic frequency equals the droplet’s frequency, heightened droplet responses are observed with the maximum amplitude of the shape oscillation. The experimental results for different resonator cavity lengths, nozzle pressure ratios and droplet diameters confirm the non-linear nature of this problem, and this conclusion is in good agreement with theoretical analysis. Measurements by high speed camera have shown that the introduction of an acoustic field can greatly enhance droplet oscillation, which means with the use of an ultrasonic atomizer based on HRT, the quality of atomization and combustion can be highly improved.

Effect of acoustic exposing on blood flow in microchannel simulating stenosis

The work is dedicated to problems connected with blood clot formation and study of blood flow features in vessels with stenosis. Using high-speed recording an analysis of flow structure of biological dispersion (blood) in acoustic field of mild intensity is made. It carried out in microchannel simulating a blood vessel with stenosis made and using soft lithography technology. The flow is arranged at constant pressure drop provided by hydrostatic pump in a range of 100–800 Pa. It was found a strong influence of acoustic field on a dynamics of blood flow in a microchannel at the range of frequencies 20–500 kHz and amplitudes below than 50 kPa. Results show reciprocating movements of flow in a region of microchannel narrowing. It is found a possibility of ultrasound field impact on blood clots formed in region of vessels stenosis.

Acoustic Method of Colorado Beetle Elimination and It’s Realization

In this article the specific influence of the acoustic waves on the organisms living beings is examined. It is known that the most important resonance frequencies of human organs are in the frequency range 0.5-20 Hz. And protection against the harmful acoustic waves on the human body may be only if a person is located in an acoustic field with a frequency, which does not coincide with the resonant frequency of the person. On the contrary, we can use the influence of acoustic fields on organisms of plant pests with the frequency that corresponds to the resonant frequency of body of pests. Then the acoustic field will have a devastating effect on the plant pest. In the laboratory the deaths of the Colorado beetle under the influence of vibratory oscillation and acoustic vibrations were detected. The method and the device for its implementation were developed and described below. The author has registered in the Patent Office of Ukraine "Acoustic Solution Colorado Beetle and Device for Performing" № 25548 A 01 M 1/04, 1/18 October 30, 1998. The elimination of the Colorado beetle by influencing its body by acoustic vibrations leads to a decrease in complexity of operation while excluding toxicity. The experiment was conducted under the conditions of agricultural area using a model of the transmitter.

Radiation from 20 MeV electrons in piezoelectric single crystals in the presence of external acoustic fields

The radiation from electrons interacting with piezoelectric single crystals and the influence of acoustic fields on the frequency-temporal parameters of characteristic energy yields have been investigated experimentally. The experiments were carried out on the extracted 20 MeV electron beam of the linear accelerator LEA-50 of the Alikhanian National Scientific Laboratory. The energy distributions of specific yields of the electron radiation in quartz single crystal were obtained. The amplification of intensity and the shift of energy yields under the influence of hypersonic vibrations were observed.

Tribological Behavior of Aerosol Particles in Acoustic Field

This work investigates agglomeration process of aerosol particles in presence of acoustic field. It is shown that besides orthokinetic and hydrodynamic interaction mechanisms, tribological interaction occurs in presence of acoustic field. This interaction depends on dynamic viscosity of the gas mixture above the liquid surface. The influence of acoustic field on tribological interaction between the aerosol particles was investigated both numerically and experimentally. The obtained results show the positive influence of acoustic field on agglomeration of aerosol particles.

The influence of acoustic field and frequency on hydrodynamics of group B particles

Sound Assisted Fluidized Bed (SAFB) of group B particles (180?m glass bead) has been studied in a 46mm I.D. column with aspect ratios of 1.4 and 2.9. A loudspeaker mounted on the top of the bed was supplied by a function generator with square wave to generate the sound as the source of vibration of the fluidized bed. The sound pressure level (referred to 20?pa) was varied from 102 to 140dB and frequencies from 70Hz to 170Hz were applied. The effects of sound pressure level, sound frequency and particle loading on the properties of SAFB were investigated. The experimental result showed that the minimum fluidization velocity decreased with the increase in sound pressure level, also minimum fluidization velocity was varied with variation of frequencies. At resonance frequency minimum fluidization velocity was found to be minimum. The bed height did not show an appreciable increase in presence of high acoustic field and at resonant frequency. Minimum fluidization velocity verses frequency curve in presence of sound intensity varied with variation of bed weight.

Influence of an acoustic field on flame development and transition to detonation

The work is devoted to experimental and numerical study of flame interaction with acoustic waves in closed and semiclosed pipes filled with preliminarily mixed gaseous mixtures. We analyze the influence of eigenfield (generated by the flame itself) and external acoustic field on the flame dynamics. We show that acoustic field affects the combustion process at all stages. The effect increases with any increase in the energy of initiation of combustion. At later stages of flame development, acoustic waves can initiate the transition to detonation or prevent it. Thus, it is possible to control the combustion modes using external acoustic field.

Influence of standing sound waves on droplet combustion

The influence of acoustic fields on combustion of a single fuel droplet has been investigated using microgravity. The natural convection-free conditions allow the role of sound alone to be established by avoiding the coupling of sound-induced alternating convection and natural convection. Experiments were done with n -decane single droplets of about 1.5 mm in diameter. Sounds of 66.5 to 3353 Hz with sound pressure levels up to 135 dB were applied in a duct, which achieved maximum velocity amplitudes of about 1 m/s. As a result, a significantly deformed flame and a soot ring instead of soot shell were found in cases of large velocity amplitude. Burning rates increased with increasing velocity amplitude. The other parameters such as sound pressure level or frequency had little influence. Different influences of sound were found for droplets burning at different locations relative to the velocity antinode of the applied sound. All these observed phenomena are explained by the alternating convection due to sound and a unidirectional convection, which is a form of acoustic streaming, driven by the acoustic radiation force. A simple analysis has been made of the streaming mechanism and the increased burning rate. Differences with droplet location are explained by the enhancement in heat and mass transfer due to the two kinds of convection.

Influence of acoustic fields on drop dynamics in an acoustic resonator

Capillary waves on a liquid sphere may be excited by acoustic fields, especially due to the higher harmonics of the resonant acoustic fields. The growth of the capillary waves has been analytically discussed. For a manipulation of weightless molten material without contacts, rotation of a liquid drop by acoustic waves is important. Approximate solutions to govern the dynamics of capillary waves on a rotating liquid drop has been analytically derived. Instabilities of multi-lobed waves due to a rotational flow in the perturbed flow field and due to the acoustic fields have been discussed.