In-situ stress is a common stress in the exploration and development of oil reservoirs. Therefore, it is of great significance to study the propagation characteristics of borehole acoustic waves in fluid-saturated por...In-situ stress is a common stress in the exploration and development of oil reservoirs. Therefore, it is of great significance to study the propagation characteristics of borehole acoustic waves in fluid-saturated porous media under stress.Based on the acoustoelastic theory of fluid-saturated porous media, the field equation of fluid-saturated porous media under the conditions of confining pressure and pore pressure and the acoustic field formula of multipole source excitation in open hole are given. The influences of pore pressure and confining pressure on guided waves of multipole borehole acoustic field in fluid-saturated porous media are investigated. The numerical results show that the phase velocity and excitation intensity of guided wave increase significantly under the confining pressure. For a given confining pressure, the phase velocity of the guided wave decreases with pore pressure increasing. The excitation intensity of guided wave increases at low frequency and then decreases at high frequency with pore pressure increasing, except for that of Stoneley wave which decreases in the whole frequency range. These results will help us get an insight into the influences of confining pressure and pore pressure on the acoustic field of multipole source in borehole around fluid-saturated porous media.展开更多
Acoustic scattering modulation caused by an undulating sea surface on the space-time dimension seriously affects underwater detection and target recognition.Herein,underwater acoustic scattering modulation from a movi...Acoustic scattering modulation caused by an undulating sea surface on the space-time dimension seriously affects underwater detection and target recognition.Herein,underwater acoustic scattering modulation from a moving rough sea surface is studied based on integral equation and parabolic equation.And with the principles of grating and constructive interference,the mechanism of this acoustic scattering modulation is explained.The periodicity of the interference of moving rough sea surface will lead to the interference of the scattering field at a series of discrete angles,which will form comb-like and frequency-shift characteristics on the intensity and the frequency spectrum of the acoustic scattering field,respectively,which is a high-order Bragg scattering phenomenon.Unlike the conventional Doppler effect,the frequency shifts of the Bragg scattering phenomenon are multiples of the undulating sea surface frequency and are independent of the incident sound wave frequency.Therefore,even if a low-frequency underwater acoustic field is incident,it will produce obvious frequency shifts.Moreover,under the action of ideal sinusoidal waves,swells,fully grown wind waves,unsteady wind waves,or mixed waves,different moving rough sea surfaces create different acoustic scattering processes and possess different frequency shift characteristics.For the swell wave,which tends to be a single harmonic wave,the moving rough sea surface produces more obvious high-order scattering and frequency shifts.The same phenomena are observed on the sea surface under fully grown wind waves,however,the frequency shift slightly offsets the multiple peak frequencies of the wind wave spectrum.Comparing with the swell and fully-grown wind waves,the acoustic scattering and frequency shift are not obvious for the sea surface under unsteady wind waves.展开更多
In earlier approach, the 2-D acoustical field profiles on the substrate region are often calculated with BPM. In this paper, we present a new approach based on the finite element -artificial transmitting boundary meth...In earlier approach, the 2-D acoustical field profiles on the substrate region are often calculated with BPM. In this paper, we present a new approach based on the finite element -artificial transmitting boundary method and calculate acoustical field on the substrate region.展开更多
Transducers that are widely applied in cement bond evaluation tools, such as cement bond logs and variable density logs, cannot radiate acoustic energy directionally because of the characteristics of monopole sources....Transducers that are widely applied in cement bond evaluation tools, such as cement bond logs and variable density logs, cannot radiate acoustic energy directionally because of the characteristics of monopole sources. A phased arc array transmitter, which is a novel transducer that differs from monopole and dipole transducers, is presented in this study. To simulate the acoustic field generated by a phased arc array in a fluid-filled cased borehole with different channelings, a 3D finite-difference time-domain method is adopted. The acoustic field generated by a traditional monopole source is also simulated and compared with the field generated by the phased arc array transmitter. Numerical simulation results show that the phased arc array radiates energy directionally in a narrow angular range in the borehole, thereby compressing the acoustic energy into a narrow range in the casing pipe, the cement, and the formation. We present the analyses of first-arrival waveforms and the amplitudes of casing waves at different azimuthal angles for the two different sources. The results indicate that employing a directional source facilitates azimuthal identification and analysis of possible channeling behind the casing pipe.展开更多
The acoustic tools widely used in borehole well logging and being developed in borehole acoustic reflection imaging do not have the function of azimuthal measurement due to a symmetric source, so they can not be used ...The acoustic tools widely used in borehole well logging and being developed in borehole acoustic reflection imaging do not have the function of azimuthal measurement due to a symmetric source, so they can not be used to evaluate the azimuthal character of borehole formation. In this paper, a 3D finite difference method was used to simulate the acoustic fields in a fluid-filled borehole generated by a traditional monopole source and a phased arc array. Acoustic waveforms were presented for both cases. The analysis of the simulated waveforms showed that different from the monopole source, the acoustic energy generated by the phased arc array transmitter mainly radiated to the borehole in a narrow azimuthal range, which was the key technique to implement azimuthal acoustic well logging. Similar to the monopole source, the waveforms generated by the phased arc array in the fluid-filled borehole also contain compressional (P) waves and shear (S) waves refracted along the borehole, which is the theoretical foundation of phased arc array acoustic well logging.展开更多
The horizontal-longitudinal correlations of the acoustic field in deep water are investigated based on the experi- mental data obtained in the South China Sea. It is shown that the horizontal-longitudinal correlation ...The horizontal-longitudinal correlations of the acoustic field in deep water are investigated based on the experi- mental data obtained in the South China Sea. It is shown that the horizontal-longitudinal correlation coefficients in the convergence zone are high, and the correlation length is consistent with the convergence zone width, which depends on the receiver depth and range. The horizontal-longitudinal correlation coefficients in the convergence zone also have a division structure for the deeper receiver. The signals from the second part of the convergence zone are still correlated with the reference signal in the first part. The horizontal-longitudinal correlation coeffi- cients in the shadow zone are lower than that in the convergence zone, and the correlation length in the shadow zone is also much shorter than that in the convergence zone. The numerical simulation results by using the normal modes theory are qualitatively consistent with the experimental results.展开更多
In the semi-free acoustic field, the actual acoustic pressure at any point is composed of two parts: The direct acoustic pressure and the reflected acoustic pressure. The general acoustic holographic theories and alg...In the semi-free acoustic field, the actual acoustic pressure at any point is composed of two parts: The direct acoustic pressure and the reflected acoustic pressure. The general acoustic holographic theories and algorithms request that there is only the direct acoustic pressure contained in the pressure at any point on the hologram surface, consequently, they cannot be used to reconstruct acoustic source and predict acoustic field directly. To take the reflected pressure into consideration, near-field acoustic holography for semi-free acoustic field based on wave superposition approach is proposed to realize the holographic reconstruction and prediction of the semi-free acoustic field, and the wave superposition approach is adopted as a holographic transform algorithm. The proposed theory and algorithm are realized and verified with a numerical example, and the drawbacks of the general theories and algorithms in the holographic reconstruction and prediction of the semi-free acoustic field are also demonstrated by this numerical example.展开更多
The horizontal-longitudinal correlation of acoustic field for the receiver near the bottom is analyzed by using nu- merical modeling. An approximate analytical solution of horizontal-longitudinal correlation coefficie...The horizontal-longitudinal correlation of acoustic field for the receiver near the bottom is analyzed by using nu- merical modeling. An approximate analytical solution of horizontal-longitudinal correlation coefficient is derived based on the ray method. Combining the characteristic of Lloyd's mirror interference pattern, the variability of acoustic field and its effect on horizontal-longitudinal spatial correlation are discussed. The theoretical pre- diction agrees well with the numerical results. Experimental results confirm the validity of analytical solution. Finally, the applicability of the analytical solution is summarized. The conclusion is beneficial for the design of bottom-moored array and the estimation of integral time for moving source localization.展开更多
The pressure and horizontal particle velocity combined descriptions in the very low frequency acoustic field of shallow wa- ter integrated with the concept of effective depth of Pekeris wave- guide is proposed, especi...The pressure and horizontal particle velocity combined descriptions in the very low frequency acoustic field of shallow wa- ter integrated with the concept of effective depth of Pekeris wave- guide is proposed, especially the active component of the pressure and horizontal particle velocity cross-spectrum, also called ho- rizontal complex cross acoustic intensity, when only two normal modes are trapped in the waveguide. Both the approximate theo- retic analysis and the numerical results show that the sign of the horizontal complex cross acoustic intensity active component is independent of the range when vertically deployed receiving dual sensors are placed in appropriate depths, the sum of which is equal to the waveguide effective depth, so it can be used to tell whether the sound source is near the surface or underwater; while the range rate is expected to be measured by utilizing the sign distribution characteristic of the reactive component. The further robustness analysis of the depth classification algorithm shows that the existence of shear waves in semi infinite basement and the change of acoustic velocity profiles have few effects on the application of this method, and the seabed attenuation will limit the detection range, but the algorithm still has a good robustness in the valid detection range.展开更多
We developed a parallelized scheme of 3D finite difference (3DFD)with non-oniform staggered grid to simulate the eccentric borehole acoustic field with side-wall acoustic logging tools in open and cased wells. Highe...We developed a parallelized scheme of 3D finite difference (3DFD)with non-oniform staggered grid to simulate the eccentric borehole acoustic field with side-wall acoustic logging tools in open and cased wells. Higher accuracy and lower computation cost were achieved with this scheme for modeling such an asymmetric wave field generated by a high frequency source near or on the borehole wall. We also modeled the cases with and without considering the effects of the tool body. The simulation results demonstrated that the logging tool body would attenuate the direct waves but have only little influence on the interface waves in such a borehole condition. The effects of the tool body on the wave field were significant only when the contrast of the elastic properties between tool body and borehole fluid was large.展开更多
The present study analyzes the effect of stirring on ultrasonic degradation experiments through acoustic field distribution,which provides a guidance for further improvement of the degradation rate of organic solution...The present study analyzes the effect of stirring on ultrasonic degradation experiments through acoustic field distribution,which provides a guidance for further improvement of the degradation rate of organic solutions.It is known that in order to eliminate the standing wave field formed by ultrasonic radiation in the water tank,the liquid in the water tank needs to be stirred and the corresponding distribution of acoustic field is simulated by using the finite element method(FEM).The standing wave leads to an uneven distribution of the acoustic field when it is not stirred,and disappears after being stirred,which increases the cavitation area in the ultrasonic cleaning tank.Then,the degradation experiment with agitation is carried out.The experimental results show that the degradation rate of the solution is higher than that when there is no agitation,which confirms the importance of the acoustic field distribution to ultrasonic degradation.In addition,it is clear that with the increase of the stirring speed,the degradation rate increases first and reaches a maximum at 600 rpm before decreasing.Finally,the distribution of flow field is simulated and analyzed.展开更多
The shape of aluminum alloy extrudate used in high-speed train is complex, structural noises from the surfaces of the extrudate will be received when using ultrasonic phased array to detect the flaws in FSW. To solve ...The shape of aluminum alloy extrudate used in high-speed train is complex, structural noises from the surfaces of the extrudate will be received when using ultrasonic phased array to detect the flaws in FSW. To solve this problem, ultrasonic phased array acoustic field model and propagation simulation of acoustic waves were introduced to simulate the acoustic pressure distribution and the propagation of the acoustic waves. With the methods above, the detection parameters can be optimized and as a result, the experimental process can be simplified and the detection efficiency can be improved. Meanwhile, the echoes in the S-scan images can be predicted, which can help analyze the detection results and judge the defects.展开更多
In this paper, by using functional analysis and integral equation method, we obtain some results about the properties of far field of acoustic waves in an inhomogeneous medium. And we also discuss some ill-posed inver...In this paper, by using functional analysis and integral equation method, we obtain some results about the properties of far field of acoustic waves in an inhomogeneous medium. And we also discuss some ill-posed inverse scattering problems by Tikhonov regularization method.展开更多
Interdigitated transducers(IDTs)were originally designed as delay lines for radars.Half a century later,they have found new life as actuators for microfluidic systems.By generating strong acoustic fields,they trigger ...Interdigitated transducers(IDTs)were originally designed as delay lines for radars.Half a century later,they have found new life as actuators for microfluidic systems.By generating strong acoustic fields,they trigger nonlinear effects that enable pumping and mixing of fluids,and moving particles without contact.However,the transition from signal processing to actuators comes with a range of challenges concerning power density and spatial resolution that have spurred exciting developments in solid-state acoustics and especially in IDT design.Assuming some familiarity with acoustofluidics,this paper aims to provide a tutorial for IDT design and characterization for the purpose of acoustofluidic actuation.It is targeted at a diverse audience of researchers in various fields,including fluid mechanics,acoustics,and microelectronics.展开更多
The search for the development of a reliable mathematical model for understanding bubble dynamics behavior is an ongoing endeavor.A long list of complex phenomena underlies the physics of this problem.In the past deca...The search for the development of a reliable mathematical model for understanding bubble dynamics behavior is an ongoing endeavor.A long list of complex phenomena underlies the physics of this problem.In the past decades,the lattice Boltzmann method has emerged as a promising tool to address such complexities.In this regard,we have applied a 121-velocity multiphase lattice Boltzmann model to an asymmetric cluster of bubbles in an acoustic field.A problem as a benchmark is studied to check the consistency and applicability of the model.The problem of interest is to study the deformation and coalescence phenomena in bubble cluster dynamics,as well as the screening effect on an acoustic multibubble medium.It has been observed that the LB model is able to simulate the combination of the three aforementioned phenomena for a bubble cluster as a whole and for every individual bubble in the cluster.展开更多
Based on cavity resonance and sandwich composite plate (3D) theoretical model for frequency dispersion characterization theory, this paper presents a universal three-dimensional and displacement profile shapes of th...Based on cavity resonance and sandwich composite plate (3D) theoretical model for frequency dispersion characterization theory, this paper presents a universal three-dimensional and displacement profile shapes of the film bulk acoustic resonator (FBARs). This model provides results of FBAR excited thickness-extensional and flexure modes, and the result of frequency dispersion is proposed in which the thicknesses and impedance of the electrodes and the piezoelectric material are taken into consideration; its further simplification shows good agreement with the modified Butterworth-Van-Dyke (MBVD) model. The displacement profile reflects the vibration stress distribution of electrode shapes and the lateral resonance effect, which depends on the axis ratio of the electrode shapes a/b. The results are consistent with the 3D finite element method modeling and laser interferometry measurement in general.展开更多
As a clean,efficient,and sustainable energy,hydrogen is expected to replace traditional fossil energy.A series of studies focusing on morphology regulation,surface modification,and structural reconstruction have been ...As a clean,efficient,and sustainable energy,hydrogen is expected to replace traditional fossil energy.A series of studies focusing on morphology regulation,surface modification,and structural reconstruction have been devoted to improving the intrinsic catalytic activity of non-noble metal catalysts.However,complex system structure design and the mutual interference of various chemical components would hinder the further improvement of hydrogen evolution performance.In recent years,external field assisted hydrogen evolution reaction(HER)has become a new research hotspot.Herein,we systematically summarize the promoting effects of various external fields on catalytic hydrogen production from the aspects of system design and catalytic mechanism,including electric field,thermal field,optical field,magnetic field,and acoustic field.Ultimately,we discuss the key challenges facing this external field regulation strategy and put forward the prospect of future research topics.We sincerely expect that this review could not only provide a new insight into the basic mechanism of external-assisted catalysis,but also promote further research on improving HER performance from a more diverse and comprehensive perspective.展开更多
Being an emerging body-shaping technology of fat cell disruption,high-intensity focused ultrasound has been investigated intensively in recent years for its favorable natures such as painlessness,safety and noninvasio...Being an emerging body-shaping technology of fat cell disruption,high-intensity focused ultrasound has been investigated intensively in recent years for its favorable natures such as painlessness,safety and noninvasion.One of the major problems for the technology,however,is the overheating of transducers.In this study,we modified the transducer design in order to solve the overheating problem.We simulated the performance of the modified design by finite element analysis and fabricated the newly designed transducer.By measuring the actual performance data,we proved that the new design can effectively reduce temperature rise while keeping the acoustic intensity field unaffected.展开更多
This investigation was performed to study acoustic field signal in order to improve RSW quality. Researchers firstly built an acoustic array sensor system, which included 8 MPA-416 acoustic sensors, data acquisition c...This investigation was performed to study acoustic field signal in order to improve RSW quality. Researchers firstly built an acoustic array sensor system, which included 8 MPA-416 acoustic sensors, data acquisition card and LabVIEW. The system obtained the acoustic field information in the process of nugget growing. Due to the nonlinearity field signal, array sensor algorithm was utilized to quantitatively analyze the characteristics of acoustie field and reduced noise. The experiment and calculation results show that array sensor system can acquire acoustic field signal of nugget growing in the RSW process and array processing algorithm based on acoustic field can extract characteristic parameters to evaluate RSW quality. It was concluded that the acoustic array sensor system offers a new methodology for RSW quality inspection.展开更多
Magnetic field and acoustic field coupled imaging methods mainly include magnetoacoustic tomography,magneto-acousto-electrical tomography,and thermoacoustic tomography,all of which non-invasively achieve the electrica...Magnetic field and acoustic field coupled imaging methods mainly include magnetoacoustic tomography,magneto-acousto-electrical tomography,and thermoacoustic tomography,all of which non-invasively achieve the electrical conductivity imaging of tissues with a resolution of up to the millimeter scale.The principles of these three imaging methods and the research progress in the last two decades are reviewed.First,the principles of the three magnetic and acoustic field coupled methods are individually introduced.The progress in medical electromagnetic imaging is further elaborated,and finally the future directions and summary of the coupled imaging methods are summarized.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.42074139)the Natural Science Foundation of Jilin Province,China (Grant No.20210101140JC)。
文摘In-situ stress is a common stress in the exploration and development of oil reservoirs. Therefore, it is of great significance to study the propagation characteristics of borehole acoustic waves in fluid-saturated porous media under stress.Based on the acoustoelastic theory of fluid-saturated porous media, the field equation of fluid-saturated porous media under the conditions of confining pressure and pore pressure and the acoustic field formula of multipole source excitation in open hole are given. The influences of pore pressure and confining pressure on guided waves of multipole borehole acoustic field in fluid-saturated porous media are investigated. The numerical results show that the phase velocity and excitation intensity of guided wave increase significantly under the confining pressure. For a given confining pressure, the phase velocity of the guided wave decreases with pore pressure increasing. The excitation intensity of guided wave increases at low frequency and then decreases at high frequency with pore pressure increasing, except for that of Stoneley wave which decreases in the whole frequency range. These results will help us get an insight into the influences of confining pressure and pore pressure on the acoustic field of multipole source in borehole around fluid-saturated porous media.
基金Project supported by the IACAS Young Elite Researcher Project(Grant No.QNYC201703)the Rising Star Foundation of Integrated Research Center for Islands and Reefs Sciences,CAS(Grant No.ZDRW-XH-2021-2-04)the Key Laboratory Foundation of Acoustic Science and Technology(Grant No.2021-JCJQ-LB-066-08).
文摘Acoustic scattering modulation caused by an undulating sea surface on the space-time dimension seriously affects underwater detection and target recognition.Herein,underwater acoustic scattering modulation from a moving rough sea surface is studied based on integral equation and parabolic equation.And with the principles of grating and constructive interference,the mechanism of this acoustic scattering modulation is explained.The periodicity of the interference of moving rough sea surface will lead to the interference of the scattering field at a series of discrete angles,which will form comb-like and frequency-shift characteristics on the intensity and the frequency spectrum of the acoustic scattering field,respectively,which is a high-order Bragg scattering phenomenon.Unlike the conventional Doppler effect,the frequency shifts of the Bragg scattering phenomenon are multiples of the undulating sea surface frequency and are independent of the incident sound wave frequency.Therefore,even if a low-frequency underwater acoustic field is incident,it will produce obvious frequency shifts.Moreover,under the action of ideal sinusoidal waves,swells,fully grown wind waves,unsteady wind waves,or mixed waves,different moving rough sea surfaces create different acoustic scattering processes and possess different frequency shift characteristics.For the swell wave,which tends to be a single harmonic wave,the moving rough sea surface produces more obvious high-order scattering and frequency shifts.The same phenomena are observed on the sea surface under fully grown wind waves,however,the frequency shift slightly offsets the multiple peak frequencies of the wind wave spectrum.Comparing with the swell and fully-grown wind waves,the acoustic scattering and frequency shift are not obvious for the sea surface under unsteady wind waves.
基金This work was supported by the National Natural Science Fund of China (10084001) the Action Plan for Booming Education of Tianjin University.
文摘In earlier approach, the 2-D acoustical field profiles on the substrate region are often calculated with BPM. In this paper, we present a new approach based on the finite element -artificial transmitting boundary method and calculate acoustical field on the substrate region.
基金supported by the National Natural ScienceFoundation of China (Grant Nos. 11204380, 11374371, 11134011 and 61102102)National Science and Technology Major Project (Grant No. 2011ZX05020-009)PetroChina Innovation Foundation (2013D-5006-0304)
文摘Transducers that are widely applied in cement bond evaluation tools, such as cement bond logs and variable density logs, cannot radiate acoustic energy directionally because of the characteristics of monopole sources. A phased arc array transmitter, which is a novel transducer that differs from monopole and dipole transducers, is presented in this study. To simulate the acoustic field generated by a phased arc array in a fluid-filled cased borehole with different channelings, a 3D finite-difference time-domain method is adopted. The acoustic field generated by a traditional monopole source is also simulated and compared with the field generated by the phased arc array transmitter. Numerical simulation results show that the phased arc array radiates energy directionally in a narrow angular range in the borehole, thereby compressing the acoustic energy into a narrow range in the casing pipe, the cement, and the formation. We present the analyses of first-arrival waveforms and the amplitudes of casing waves at different azimuthal angles for the two different sources. The results indicate that employing a directional source facilitates azimuthal identification and analysis of possible channeling behind the casing pipe.
基金supported by the National Natural ScienceFoundation of China(Grant Nos.10534040,40574049 and 40874097)the Research Fund for the Doctoral Programof Higher Education(Grant No.20070425028)the Foundation of State Key Laboratory of Petroleum Resourceand Prospecting,China University of Petroleum(Grant No.PRPDX2008-08).
文摘The acoustic tools widely used in borehole well logging and being developed in borehole acoustic reflection imaging do not have the function of azimuthal measurement due to a symmetric source, so they can not be used to evaluate the azimuthal character of borehole formation. In this paper, a 3D finite difference method was used to simulate the acoustic fields in a fluid-filled borehole generated by a traditional monopole source and a phased arc array. Acoustic waveforms were presented for both cases. The analysis of the simulated waveforms showed that different from the monopole source, the acoustic energy generated by the phased arc array transmitter mainly radiated to the borehole in a narrow azimuthal range, which was the key technique to implement azimuthal acoustic well logging. Similar to the monopole source, the waveforms generated by the phased arc array in the fluid-filled borehole also contain compressional (P) waves and shear (S) waves refracted along the borehole, which is the theoretical foundation of phased arc array acoustic well logging.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11434012 and 11174312
文摘The horizontal-longitudinal correlations of the acoustic field in deep water are investigated based on the experi- mental data obtained in the South China Sea. It is shown that the horizontal-longitudinal correlation coefficients in the convergence zone are high, and the correlation length is consistent with the convergence zone width, which depends on the receiver depth and range. The horizontal-longitudinal correlation coefficients in the convergence zone also have a division structure for the deeper receiver. The signals from the second part of the convergence zone are still correlated with the reference signal in the first part. The horizontal-longitudinal correlation coeffi- cients in the shadow zone are lower than that in the convergence zone, and the correlation length in the shadow zone is also much shorter than that in the convergence zone. The numerical simulation results by using the normal modes theory are qualitatively consistent with the experimental results.
基金This project is supported by National Natural Science Foundation of China (No.10504006, No.50575063).
文摘In the semi-free acoustic field, the actual acoustic pressure at any point is composed of two parts: The direct acoustic pressure and the reflected acoustic pressure. The general acoustic holographic theories and algorithms request that there is only the direct acoustic pressure contained in the pressure at any point on the hologram surface, consequently, they cannot be used to reconstruct acoustic source and predict acoustic field directly. To take the reflected pressure into consideration, near-field acoustic holography for semi-free acoustic field based on wave superposition approach is proposed to realize the holographic reconstruction and prediction of the semi-free acoustic field, and the wave superposition approach is adopted as a holographic transform algorithm. The proposed theory and algorithm are realized and verified with a numerical example, and the drawbacks of the general theories and algorithms in the holographic reconstruction and prediction of the semi-free acoustic field are also demonstrated by this numerical example.
基金Supported by the National Natural Science Foundation of China under Grant No 11174235
文摘The horizontal-longitudinal correlation of acoustic field for the receiver near the bottom is analyzed by using nu- merical modeling. An approximate analytical solution of horizontal-longitudinal correlation coefficient is derived based on the ray method. Combining the characteristic of Lloyd's mirror interference pattern, the variability of acoustic field and its effect on horizontal-longitudinal spatial correlation are discussed. The theoretical pre- diction agrees well with the numerical results. Experimental results confirm the validity of analytical solution. Finally, the applicability of the analytical solution is summarized. The conclusion is beneficial for the design of bottom-moored array and the estimation of integral time for moving source localization.
基金supported by the National Natural Science Foundation of China(1140440611374072)
文摘The pressure and horizontal particle velocity combined descriptions in the very low frequency acoustic field of shallow wa- ter integrated with the concept of effective depth of Pekeris wave- guide is proposed, especially the active component of the pressure and horizontal particle velocity cross-spectrum, also called ho- rizontal complex cross acoustic intensity, when only two normal modes are trapped in the waveguide. Both the approximate theo- retic analysis and the numerical results show that the sign of the horizontal complex cross acoustic intensity active component is independent of the range when vertically deployed receiving dual sensors are placed in appropriate depths, the sum of which is equal to the waveguide effective depth, so it can be used to tell whether the sound source is near the surface or underwater; while the range rate is expected to be measured by utilizing the sign distribution characteristic of the reactive component. The further robustness analysis of the depth classification algorithm shows that the existence of shear waves in semi infinite basement and the change of acoustic velocity profiles have few effects on the application of this method, and the seabed attenuation will limit the detection range, but the algorithm still has a good robustness in the valid detection range.
文摘We developed a parallelized scheme of 3D finite difference (3DFD)with non-oniform staggered grid to simulate the eccentric borehole acoustic field with side-wall acoustic logging tools in open and cased wells. Higher accuracy and lower computation cost were achieved with this scheme for modeling such an asymmetric wave field generated by a high frequency source near or on the borehole wall. We also modeled the cases with and without considering the effects of the tool body. The simulation results demonstrated that the logging tool body would attenuate the direct waves but have only little influence on the interface waves in such a borehole condition. The effects of the tool body on the wave field were significant only when the contrast of the elastic properties between tool body and borehole fluid was large.
基金supported by the National Natural Science Foundation of China(Grant Nos.11674207 and 11674206)。
文摘The present study analyzes the effect of stirring on ultrasonic degradation experiments through acoustic field distribution,which provides a guidance for further improvement of the degradation rate of organic solutions.It is known that in order to eliminate the standing wave field formed by ultrasonic radiation in the water tank,the liquid in the water tank needs to be stirred and the corresponding distribution of acoustic field is simulated by using the finite element method(FEM).The standing wave leads to an uneven distribution of the acoustic field when it is not stirred,and disappears after being stirred,which increases the cavitation area in the ultrasonic cleaning tank.Then,the degradation experiment with agitation is carried out.The experimental results show that the degradation rate of the solution is higher than that when there is no agitation,which confirms the importance of the acoustic field distribution to ultrasonic degradation.In addition,it is clear that with the increase of the stirring speed,the degradation rate increases first and reaches a maximum at 600 rpm before decreasing.Finally,the distribution of flow field is simulated and analyzed.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 51175113 ).
文摘The shape of aluminum alloy extrudate used in high-speed train is complex, structural noises from the surfaces of the extrudate will be received when using ultrasonic phased array to detect the flaws in FSW. To solve this problem, ultrasonic phased array acoustic field model and propagation simulation of acoustic waves were introduced to simulate the acoustic pressure distribution and the propagation of the acoustic waves. With the methods above, the detection parameters can be optimized and as a result, the experimental process can be simplified and the detection efficiency can be improved. Meanwhile, the echoes in the S-scan images can be predicted, which can help analyze the detection results and judge the defects.
基金Shanghai Youth Science FoundationSupported in Part by Shanghai ScienceTechnology Development Foundation
文摘In this paper, by using functional analysis and integral equation method, we obtain some results about the properties of far field of acoustic waves in an inhomogeneous medium. And we also discuss some ill-posed inverse scattering problems by Tikhonov regularization method.
基金This work was supported by the National Natural Science Foundation of China under Grant Nos.12004078 and 61874033the State Key Lab of ASIC and Systems,the Science and Technology Commission of Shanghai Municipality Award/Grant Nos.22QA1400900 and 22WZ2502200Fudan University 2021MS001,2021MS002 and 2020KF006.
文摘Interdigitated transducers(IDTs)were originally designed as delay lines for radars.Half a century later,they have found new life as actuators for microfluidic systems.By generating strong acoustic fields,they trigger nonlinear effects that enable pumping and mixing of fluids,and moving particles without contact.However,the transition from signal processing to actuators comes with a range of challenges concerning power density and spatial resolution that have spurred exciting developments in solid-state acoustics and especially in IDT design.Assuming some familiarity with acoustofluidics,this paper aims to provide a tutorial for IDT design and characterization for the purpose of acoustofluidic actuation.It is targeted at a diverse audience of researchers in various fields,including fluid mechanics,acoustics,and microelectronics.
文摘The search for the development of a reliable mathematical model for understanding bubble dynamics behavior is an ongoing endeavor.A long list of complex phenomena underlies the physics of this problem.In the past decades,the lattice Boltzmann method has emerged as a promising tool to address such complexities.In this regard,we have applied a 121-velocity multiphase lattice Boltzmann model to an asymmetric cluster of bubbles in an acoustic field.A problem as a benchmark is studied to check the consistency and applicability of the model.The problem of interest is to study the deformation and coalescence phenomena in bubble cluster dynamics,as well as the screening effect on an acoustic multibubble medium.It has been observed that the LB model is able to simulate the combination of the three aforementioned phenomena for a bubble cluster as a whole and for every individual bubble in the cluster.
基金supported by the National Natural Science Foundation of China(Grant No.61275081)
文摘Based on cavity resonance and sandwich composite plate (3D) theoretical model for frequency dispersion characterization theory, this paper presents a universal three-dimensional and displacement profile shapes of the film bulk acoustic resonator (FBARs). This model provides results of FBAR excited thickness-extensional and flexure modes, and the result of frequency dispersion is proposed in which the thicknesses and impedance of the electrodes and the piezoelectric material are taken into consideration; its further simplification shows good agreement with the modified Butterworth-Van-Dyke (MBVD) model. The displacement profile reflects the vibration stress distribution of electrode shapes and the lateral resonance effect, which depends on the axis ratio of the electrode shapes a/b. The results are consistent with the 3D finite element method modeling and laser interferometry measurement in general.
基金This work was financially supported by the National Natural Science Foundation of China(No.51902101)the Youth Natural Science Foundation of Hunan Province(No.2021JJ40044)+2 种基金Natural Science Foundation of Jiangsu Province(No.BK20201381)Science Foundation of Nanjing University of Posts and Telecommunications(Nos.NY219144 and NY221046)the National College Student Innovation and Entrepreneurship Training Program(No.202210293017Z).
文摘As a clean,efficient,and sustainable energy,hydrogen is expected to replace traditional fossil energy.A series of studies focusing on morphology regulation,surface modification,and structural reconstruction have been devoted to improving the intrinsic catalytic activity of non-noble metal catalysts.However,complex system structure design and the mutual interference of various chemical components would hinder the further improvement of hydrogen evolution performance.In recent years,external field assisted hydrogen evolution reaction(HER)has become a new research hotspot.Herein,we systematically summarize the promoting effects of various external fields on catalytic hydrogen production from the aspects of system design and catalytic mechanism,including electric field,thermal field,optical field,magnetic field,and acoustic field.Ultimately,we discuss the key challenges facing this external field regulation strategy and put forward the prospect of future research topics.We sincerely expect that this review could not only provide a new insight into the basic mechanism of external-assisted catalysis,but also promote further research on improving HER performance from a more diverse and comprehensive perspective.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.10904093 and 61031003)the Science and Technology Grant Scheme funds from Shenzhen Government(No.08CXY-23).
文摘Being an emerging body-shaping technology of fat cell disruption,high-intensity focused ultrasound has been investigated intensively in recent years for its favorable natures such as painlessness,safety and noninvasion.One of the major problems for the technology,however,is the overheating of transducers.In this study,we modified the transducer design in order to solve the overheating problem.We simulated the performance of the modified design by finite element analysis and fabricated the newly designed transducer.By measuring the actual performance data,we proved that the new design can effectively reduce temperature rise while keeping the acoustic intensity field unaffected.
基金support for this research from the Natural Science Foundation of China (No.50575159)project of Chinese Ministry of Education (No.106049, 20060056058)+1 种基金Natural Science Foundation of Tianjin (06YFJMJC03400)Natural High-tech R&D 863 Program (2008AA04Z136)
文摘This investigation was performed to study acoustic field signal in order to improve RSW quality. Researchers firstly built an acoustic array sensor system, which included 8 MPA-416 acoustic sensors, data acquisition card and LabVIEW. The system obtained the acoustic field information in the process of nugget growing. Due to the nonlinearity field signal, array sensor algorithm was utilized to quantitatively analyze the characteristics of acoustie field and reduced noise. The experiment and calculation results show that array sensor system can acquire acoustic field signal of nugget growing in the RSW process and array processing algorithm based on acoustic field can extract characteristic parameters to evaluate RSW quality. It was concluded that the acoustic array sensor system offers a new methodology for RSW quality inspection.
基金Supported by the National Natural Science Foundation of China(52007182,51937010).
文摘Magnetic field and acoustic field coupled imaging methods mainly include magnetoacoustic tomography,magneto-acousto-electrical tomography,and thermoacoustic tomography,all of which non-invasively achieve the electrical conductivity imaging of tissues with a resolution of up to the millimeter scale.The principles of these three imaging methods and the research progress in the last two decades are reviewed.First,the principles of the three magnetic and acoustic field coupled methods are individually introduced.The progress in medical electromagnetic imaging is further elaborated,and finally the future directions and summary of the coupled imaging methods are summarized.