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Effects of confining pressure and pore pressure on multipole borehole acoustic field in fluid-saturated porous media
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作者 赵志强 刘金霞 +1 位作者 刘建宇 崔志文 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第1期468-476,共9页
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
关键词 confining pressure pore pressure fluid-saturated porous media multipole borehole acoustic field
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A Numerical Investigation of the Effect of Boundary Conditions on Acoustic Pressure Distribution in a Sonochemical Reactor Chamber
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作者 Ivan Sboev Tatyana Lyubimova +1 位作者 Konstantin Rybkin Michael Kuchinskiy 《Fluid Dynamics & Materials Processing》 EI 2024年第6期1425-1439,共15页
The intensification of physicochemical processes in the sonochemical reactor chamber is widely used in problems of synthesis,extraction and separation.One of the most important mechanisms at play in such processes is ... The intensification of physicochemical processes in the sonochemical reactor chamber is widely used in problems of synthesis,extraction and separation.One of the most important mechanisms at play in such processes is the acoustic cavitation due to the non-uniform distribution of acoustic pressure in the chamber.Cavitation has a strong impact on the surface degradation mechanisms.In this work,a numerical calculation of the acoustic pressure distribution inside the reactor chamber was performed using COMSOL Multiphysics.The numerical results have revealed the dependence of the structure of the acoustic pressure field on the boundary conditions for various thicknesses of the piezoelectric transducer.In particular,the amplitude of the acoustic pressure is minimal in the case of absorbing boundaries,and the attenuation becomes more significant as the thickness of the piezoelectric transducer increases.In addition,reflective boundaries play a significant role in the formation and distribution of zones of maximum cavitation activity. 展开更多
关键词 ULTRASOUND numerical simulation acoustic pressure field cavitation erosion foil test
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Numerical simulation of acoustic pressure field for ultrasonic grain refinement of AZ80 magnesium alloy 被引量:6
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作者 邵志文 乐启炽 +1 位作者 张志强 崔建忠 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2011年第11期2476-2483,共8页
Ultrasound with different intensities was applied to treating AZ80 alloy melt to improve its solidification structure.The average grain size of the alloy could be decreased from 303 to 148 μm after the ultrasound wit... Ultrasound with different intensities was applied to treating AZ80 alloy melt to improve its solidification structure.The average grain size of the alloy could be decreased from 303 to 148 μm after the ultrasound with intensity of 30.48 W/cm2 was applied.To gain insight into the mechanism of ultrasonic treatment which affected the microstructure of the alloy,numerical simulations were carried out and the effects of different ultrasonic pressures on the behaviors of cavitation bubble in the melt were studied.The ultrasonic field propagation in the melt was also characterized.The results show that samples from different positions are subjected to different acoustic pressures and the effect of grain refinement by ultrasonic treatment for these samples is different.With the increase of ultrasonic intensity,the acoustic pressure is increased and the grain size is decreased generally. 展开更多
关键词 numerical simulation acoustic pressure ultrasonic treatment grain refinement magnesium alloy
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Acoustic pressure simulation and experiment design in seafloor mining environment 被引量:2
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作者 ZHAO Hai-ming WANG Yan-li +2 位作者 HAN Feng-lin JI Ya-qian LUO Bo-wen 《Journal of Central South University》 SCIE EI CAS CSCD 2018年第6期1409-1417,共9页
Since the suspended sediments have severe influence on acoustic radiated field of transducer, it is significant for sonar system to analyze the influence of suspended sediments on acoustic pressure in the seafloor min... Since the suspended sediments have severe influence on acoustic radiated field of transducer, it is significant for sonar system to analyze the influence of suspended sediments on acoustic pressure in the seafloor mining environment. Based on the KZK (Khokhlov-Zabolotkaya-Kuznetsov) equation, the method of sound field analysis in turbid water is proposed. Firstly, based on the analysis of absorption in clean water and viscous absorption of suspended sediments, the sound attenuation coefficient as a function of frequency in the mining environment is calculated. Then, based on the solution of KZK equation in frequency domain, the axial sound pressure of transducer in clear water as well as turbid water is simulated using MATLAB. Simulation results show that the influence of the suspended sediments on the pressure of near field is negligible. With the increase of distance, the axial sound pressures of transducer decay rapidly. Suspended sediments seriously affect the pressure in far-field. To verify the validity of this numerical method, experiment is designed and the axial sound pressure of transducer with a frequency of 200 kHz and a beam width of 7.5~ is measured in simulated mining experiment. The results show that the simulation results agree well with the experiments, and the KZK equation can be used to calculate the sound field in turbid water. 展开更多
关键词 seafloor mining acoustic pressure KZK equation turbid seawater sound attenuation
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The Relationship of Cavitation to the Negative Acoustic Pressure Amplitude in Ultrasonic Therapy 被引量:1
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作者 范庭波 屠娟 +3 位作者 罗林姣 郭霞生 黄品同 章东 《Chinese Physics Letters》 SCIE CAS CSCD 2016年第8期59-63,共5页
The relationship between the cavitation and acoustic peak negative pressure in the high-intensity focused ultrasound (HIFU) field is analyzed in water and tissue phantom. The peak negative pressure at the focus is d... The relationship between the cavitation and acoustic peak negative pressure in the high-intensity focused ultrasound (HIFU) field is analyzed in water and tissue phantom. The peak negative pressure at the focus is determined by a hybrid approach combining the measurement with the simulation. The spheroidal beam equation is utilized to describe the nonlinear acoustic propagation. The waveform at the focus is measured by a fiber optic probe hydrophone in water. The relationship between the source pressure amplitude and the excitation voltage is determined by fitting the measured ratio of the second harmonic to the fundamental component at the focus, based on the model simulation. Then the focal negative pressure is calculated for arbitrary voltage excita- tion in water and tissue phantom. A portable B-mode ultrasound scanner is applied to monitor HIFU-indueed cavitation in real time, and a passive cavitation detection (PCD) system is used to acquire the bubble scattering signals in the HIFU focal volume for the cavitation quantification. The results show that: (1) unstable cavitation starts to appear in degassed water when the peak negative pressure of HIFU signals reaches 13.5 MPa; and (2) the cavitation activity can be detected in tissue phantom by B-mode images and in the PCD system with HIFU peak negative pressures of 9.0 MPa and 7.8 MPa, respectively, which suggests that real-time B-mode images could be used to monitor the cavitation activity in two dimensions, while PCD systems are more sensitive to detect scattering and emission signals from cavitation bubbles. 展开更多
关键词 of on HIFU The Relationship of Cavitation to the Negative acoustic pressure Amplitude in Ultrasonic Therapy in MODE is for
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Boundary normal pressure-based electrical conductivity reconstruction for magneto–acoustic tomography with magnetic induction 被引量:1
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作者 郭各朴 丁鹤平 +1 位作者 戴思捷 马青玉 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第8期193-200,共8页
As a kind of multi-physics imaging approach integrating the advantages of electrical impedance tomography and ul- trasound imaging with the improved spatial resolution and image contrast, magneto-acoustic tomography w... As a kind of multi-physics imaging approach integrating the advantages of electrical impedance tomography and ul- trasound imaging with the improved spatial resolution and image contrast, magneto-acoustic tomography with magnetic induction (MAT-MI) is demonstrated to have the capability of electrical impedance contrast imaging for biological tissues with conductivity differences. By being detected with a strong directional transducer, abrupt pressure change is proved to be generated by the gradient of the induced Lorentz force along the force direction at conductivity boundary. A simplified boundary normal pressure (BNP)-based conductivity reconstruction algorithm is proposed and the formula for conductivity distribution inside the object with the clear physical meaning of pressure derivative, is derived. Numerical simulations of acoustic pressure and conductivity reconstruction are conducted based on a 2-layer eccentric cylindrical phantom model using Hilbert transform. The reconstructed two-dimensional conductivity images accord well with the model, thus success- fully making up the deficiency of only imaging conductivity boundary in traditional MAT-MI. The proposed method is also demonstrated to have a spatial resolution of one wavelength. This study provides a new method of reconstructing accurate electrical conductivity and suggests the potential applications of MAT-MI in imaging biological tissues with conductivity difference. 展开更多
关键词 magneto-acoustic tomography with magnetic induction boundary normal pressure conductivityreconstruction pressure derivative Hilbert transform
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Cold Flow Experiments and Acoustic Investigation on Pressure Oscillation Induced by Flow Instability
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作者 陈晓龙 何国强 刘佩进 《Defence Technology(防务技术)》 SCIE EI CAS 2010年第2期85-90,共6页
Pressure oscillation in solid rocket motor is believed to be the results of the interaction between the flow instability and the acoustics of combustion chamber.Several reasonable and necessary hypothesizes are given ... Pressure oscillation in solid rocket motor is believed to be the results of the interaction between the flow instability and the acoustics of combustion chamber.Several reasonable and necessary hypothesizes are given to establish an equation to describe this coupling.A cold flow motor called CVS60D(corner vortex shedding 60°)was designed to study the flow-acoustic coupling based on theoretical analysis.Experimental investigations were carried out to determine the acoustics of CVS60D.Corner vortex shedding is generated at the backward facing step which is designed similar to the geometry of the motor with finocyl propellant after the burnout of its fins.A pintle was used to modify the velocity in the duct to change the frequency of vortex shedding.It is found that large amplitude pressure oscillation occurs when the pintle moves to a range of specific position,which indicates that the frequency of vortex shedding is close to one order of acoustic modes of combustion chamber.The amplitude of pressure oscillation changes as the pintle moves. 展开更多
关键词 propulsion system of aviation & aerospace cold flow experiment acousticS pressure oscillation flow instability
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Granite deformation and behavior of acoustic emission sequence under the temperature and pressure condition at different crust depths
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作者 蒋海昆 张流 周永胜 《Acta Seismologica Sinica(English Edition)》 CSCD 2000年第4期424-433,共10页
Results of triaxial compression experiment results show that granite rock strength increases with the depth until 30 km. In shallow crust, rock failure exhibits abrupt or quasi-abrupt instability under lower pressure.... Results of triaxial compression experiment results show that granite rock strength increases with the depth until 30 km. In shallow crust, rock failure exhibits abrupt or quasi-abrupt instability under lower pressure. Acoustic Emission (AE for short) distributed almost uniformly before and after failure. Go through downwards into the depth range with progressive failure feature, there are no or only a few number of AE before and after failure. In deeper range, rock failure shows some feature of quasi-abrupt instability under high pressure. There are still few AE before failure, but with the stick-slip, much more An events were detected after failure. Under the temperature and pressure condition of more deep crust (about 26 km), rock failure takes abrupt instability under high pressure as main feature, there are dense AE activities before failure and cumulated frequency of AE increases exponentially before the failure. In about 35 km depth range, rock strength decreases quickly with the depth and sample exhibits semi-ductile or ductile progressive fails, there are no AE being detected before and after failure. The b value of AE sequence before failure seems a little smaller than that after failure, and b value roughly decreased with depth. The numerical range of index α is the widest in about 18 km depth and becomes narrow in the condition of more shallow or more deep crust. So, when the temperature and pressure condition simulating the real environment of focal depth changes from shallow to deep in the crust, the range of a of microfracture sequence would undergo such an evolvement process that a changes from narrow to wide and then to narrow again. 展开更多
关键词 high temperature and high pressure GRANITE deformation and failure acoustic emission local scale index spectra
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Numerical Study on the Low-Frequency Pressure Fluctuation Characteristics of Liquid Oxygen Delivery System Based on Acoustic Theory 被引量:1
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作者 CHEN Erfeng ZHENG Maoqi +2 位作者 FANG Hongrong XUE Lipeng MA Fei 《Aerospace China》 2021年第2期65-72,共8页
Aiming at the low-frequency pressure fluctuation phenomena in certain liquid oxygen delivery systems during dual engine operation,a numerical study on the intrinsic frequency of the liquid oxygen delivery system was c... Aiming at the low-frequency pressure fluctuation phenomena in certain liquid oxygen delivery systems during dual engine operation,a numerical study on the intrinsic frequency of the liquid oxygen delivery system was conducted by adopting an acoustic unit in Abaqus.Factors such as condensation characteristics of the oxygen-enriched gas gas in the liquid oxygen’s pipeline between pumps,flexibility of the accumulator,and cavitation flexibility of the engine were considered in the simulation models.The simulation results show that the second order frequency of the liquid oxygen delivery system is 8.77 Hz,and the phase difference of the corresponding acoustic modal is 180°,which is the liquid circuit frequency of the small loop between the two branches of the tee.This is consistent with the low-frequency fluctuation phenomenon during flight.Moreover,the simulation results were consistent with the liquid circuit frequency solved via the transfer matrix,which also verified the effectiveness of the frequency analysis method based on acoustic theory. 展开更多
关键词 acoustic unit low-frequency pressure fluctuation liquid circuit frequency
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Impact of load impedance on the performance of a thermoacoustic system employing acoustic pressure amplifier
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作者 Ke TANG Zhong-jie HUANG +1 位作者 Tao JIN Guo-bang CHEN 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2008年第1期79-87,共9页
An acoustic pressure amplifier (APA) is capable of improving the match between a thermoacoustic engine and a load by elevating pressure ratio and acoustic power output. A standing-wave thermoacoustic engine driving a ... An acoustic pressure amplifier (APA) is capable of improving the match between a thermoacoustic engine and a load by elevating pressure ratio and acoustic power output. A standing-wave thermoacoustic engine driving a resistance- and-compliance (RC) load through an APA was simulated with linear thermoacoustics to study the impact of load impedance on the performance of the thermoacoustic system. Based on the simulation results, analysis focuses on the distribution of pressure amplitude and velocity amplitude in APA with an RC load of diverse acoustic resistances and compliance impedances. Variation of operating parameters, including pressure ratio, acoustic power, hot end temperature of stack, etc., versus impedance of the RC load is presented and analyzed according to the abovementioned distribution. A verifying experiment has been performed, which indicates that the simulation can roughly predict the system operation in the fundamental-frequency mode. 展开更多
关键词 Thermoacoustic engine acoustic pressure amplifier (APA) THERMOacousticS
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CONFINING PRESSURE EFFECT ON ACOUSTIC EMISSIONS IN ROCK FAILURE
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作者 陈忠辉 唐春安 傅宇方 《Journal of Coal Science & Engineering(China)》 1998年第1期56-63,共8页
Based on the phenomenon that acoustic emissions (AE) generated by rock mass increase suddenly because of underground excavation, time sequence of AE rate in rock failure has been discussed by using statistical damage ... Based on the phenomenon that acoustic emissions (AE) generated by rock mass increase suddenly because of underground excavation, time sequence of AE rate in rock failure has been discussed by using statistical damage theory. It has been demonstrated that how the influence of confining pressure on the deformation behavior and AE characteristics in rocks can be inferred from a simple mechanics model. The results show that loading confining pressure sharply brings out increasing of AE. On the other hand, few AE emits when confining pressure is loaded sharply, and AE occurs again when axial pressure keeps on increasing. These results have been well simulated with computer and show close correspondence with directly measured curves in experiments. 展开更多
关键词 acoustic emissions confining pressure effect rock failure
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PROGRESS OF ACOUSTIC WAVE TECHNIQUE ANDITS APPLICATION IN UNDERGROUND PRESSURE MEASUREMENT
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作者 周楚良 李新元 张晓龙 《Journal of China University of Mining and Technology》 1994年第1期80-91,共12页
This paper carries out tbe experirnent study on the correlation between am stress-strain process of rock samples and the acoustie parameter change of rock by using the measurement system of KS acoustic wave data proce... This paper carries out tbe experirnent study on the correlation between am stress-strain process of rock samples and the acoustie parameter change of rock by using the measurement system of KS acoustic wave data processing device. On the spot, the stability of surrounding rock is studied by means of experiments on the relationship between the change process (from elastie to plastic failure zone) in surrounding rock of roadway and the change law of acoustic parameters of rock. These acoustie parameters inelude wave amplitude, spectral amplitude, spectrum area, spectral density,wave veloeity and attenuation coefficient etc. 展开更多
关键词 acoustic wave technique underground pressure measurement rockmass stability
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Experimental investigations on effects of gas pressure on mechanical behaviors and failure characteristic of coals 被引量:3
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作者 Yi Xue P.G.Ranjith +2 位作者 Feng Gao Zhizhen Zhang Songhe Wang 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2023年第2期412-428,共17页
The mechanical behavior of coal is the key factor affecting underground coal mining and coalbed methane extraction.In this study,triaxial compression and seepage tests were carried out on coal at different gas pressur... The mechanical behavior of coal is the key factor affecting underground coal mining and coalbed methane extraction.In this study,triaxial compression and seepage tests were carried out on coal at different gas pressures.The mechanical properties and failure process of coal were studied,as well as the acoustic emission(AE)and strain energy.The influence of gas pressure on the mechanical parameters of this coal was analyzed.Based on the conventional energy calculation formula,the pore pressure was introduced through the effective stress formula,and each energy component of coal containing gas was refined innovatively.The contribution of gas pressure to the total energy input and dissipation during loading was quantitatively described.Finally,the influence of gas pressure on coal strength was theo-retically analyzed from the perspectives of MohreCoulomb criterion and fracture mechanics.The results show that the total absorbed energy comprises the absorbed energy in the axial pressure direction(positive)and in the confining pressure direction(negative),as well as that induced by the pore pressure(initially negative and then positive).The absorbed energy in the axial pressure direction accounts for the main proportion of the total energy absorbed by coal.The quiet period of AE in the initial stage shortens,and AE activity increases during the pre-peak stage under high gas pressure.The fractal characteristics of AE in three stages are studied using the correlation dimension.The AE process has different forms of self-similarity in various deformation stages. 展开更多
关键词 COAL Gas pressure acoustic emission(AE) Strain energy Fractal characteristics
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Rock physics model for velocity–pressure relations and its application to shale pore pressure estimation
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作者 GUO Jingyi LI Min +1 位作者 ZHUANG Mingwei SUN Yuefeng 《Petroleum Exploration and Development》 SCIE 2023年第2期404-418,共15页
Acoustic wave velocity has been commonly utilized to predict subsurface geopressure using empirical relations.Acoustic wave velocity is, however, affected by many factors. To estimate pore pressure accurately, we here... Acoustic wave velocity has been commonly utilized to predict subsurface geopressure using empirical relations.Acoustic wave velocity is, however, affected by many factors. To estimate pore pressure accurately, we here propose to use elastic rock physics models to understand and analyze quantitatively the various contributions from these different factors affecting wave velocity. We report a closed-form relationship between the frame flexibility factor(γ) in a rock physics model and differential pressure, which presents the major control of pressure on elastic properties such as bulk modulus and compressional wave velocity. For a gas-bearing shale with abundant micro-cracks and fractures, its bulk modulus is much lower at abnormally high pore pressure(high γ values) where thin cracks and flat pores are open than that at normal hydrostatic pressure(low γ values) where pores are more rounded on average. The developed relations between bulk modulus and differential pressure have been successfully applied to the Upper Ordovician Wufeng and Lower Silurian Longmaxi formations in the Dingshan area of the Sichuan Basin to map the three-dimensional spatial distribution of pore pressure in the shale, integrating core, log and seismic data. The estimated results agree well with field measurements. Pressure coefficient is positively correlated to gas content. The relations and methods reported here could be useful for hydrocarbon exploration, production, and drilling safety in both unconventional and conventional fields. 展开更多
关键词 pore pressure pressure coefficient acoustic velocity bulk modulus pore structure shale gas Upper Ordovician Wufeng Formation Lower Silurian Longmaxi Formation Sichuan Basin
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Study on Transient Properties of Levitated Object in Near-Field Acoustic Levitation 被引量:1
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作者 贾兵 陈超 赵淳生 《Communications in Theoretical Physics》 SCIE CAS CSCD 2011年第12期1119-1124,共6页
A new approach to the study on the transient properties of the levitated object in near-field acoustic levitation (NFAL) is presented. In this article, the transient response characteristics, including the levitated... A new approach to the study on the transient properties of the levitated object in near-field acoustic levitation (NFAL) is presented. In this article, the transient response characteristics, including the levitated height of an object with radius of 24 mm and thickness of 5 mm, the radial velocity and pressure difference of gas at the boundary of clearance between the levitated object and radiating surface (squeeze film), is calculated according to severa/velocity amplitudes of radiating surface. First, the basic equations in fluid areas on Arbitrary Lagrange--Euler (ALE) form are numericaJly solved by using streamline upwind petrov gaJerkin (SUPG) finite elements method. Second, the formed a/gebraic equations and solid control equations are solved by using synchronous alternating method to gain the transient messages of the levitated object and gas in the squeeze film. Through theoretical and numerical analyses, it is found that there is a oscillation time in the transient process and that the response time does not simply increase with the increasing of velocity amplitudes of radiating surface. More investigations in this paper are helpful for the understanding of the transient properties of levitated object in NFAL, which are in favor of enhancing stabilities and responsiveness of levitated object. 展开更多
关键词 near-field acoustic levitation squeeze film transient properties
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NEAR-FIELD ACOUSTIC HOLOGRAPHY FOR SEMI-FREE ACOUSTIC FIELD BASED ON WAVE SUPERPOSITION APPROACH 被引量:1
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作者 LI Weibing CHEN Jian YU Fei CHEN Xinzhao 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2006年第3期455-459,共5页
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
关键词 near-field acoustical holography Semi-free acoustic field Wave superposition approach
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Novel Method for Selection of Regularization Parameter in the Near-field Acoustic Holography
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作者 ZHANG Yongbin BI Chuanxing XU Liang CHEN Xinzhao 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2011年第2期285-292,共8页
Because of the ill-posedness of the near-field acoustic holography(NAH),the regularization method is required to stabilize the computational process of NAH.The regularization effect is related to how to select the p... Because of the ill-posedness of the near-field acoustic holography(NAH),the regularization method is required to stabilize the computational process of NAH.The regularization effect is related to how to select the parameter correctly and effectively.However the L-curve method commonly used for the selection of regularization parameters has the disadvantages of wrong selection and incorrect selection,which influences the application of NAH.For the purpose of solving the problems existed in the L-curve method,the (?)-curve method is introduced into the field of NAH,and the performance applied to NAH directly is analyzed on the basis of equivalent source method-based NAH.However,it is found out via investigations that the(?)-curve method in NAH also has the problem of wrong selection and is unable to choose the regularization parameter correctly.In order to select the parameter correctly and effectively,a novel method for selecting regularization parameters is proposed based on the original(?)-curve method,which can be called improved (?)-curve method.In the proposed method the regularization parameters are discretized linearly between the largest singular value and the smallest singular value,and the solution norm and the residual norm corresponding to these regularization parameters are also described in a linear coordinate instead of in a lg-lg coordinate,which are the two main differences compared with the L-curve and with the original(?)-curve method.In linear coordinate and using the linearly discretized regularization parameters,the solution norm is a monotonically decreasing function of the residual norm as the increase of the regularization parameter,moreover the curve is convex everywhere.So the regularization parameters can be selected correctly and effectively based on the improved(?)-curve method.Then a numerical simulation is done with a simply supported plate to verify the validity of the proposed method.Experiments with two actual sources,a clamped plate and the double speakers,are carried out to do a further demonstration.The simulation result as well as the experimental result shows that the improved(?)-curve method is efficacious and has some advantages over the L-curve method and the original(?)-curve method.The proposed novel method is able to avoid the problem of wrong selection and to select the regularization parameter correctly even if the curve is smooth. 展开更多
关键词 near-field acoustic holography(NAH) REGULARIZATION parameter selection
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Active control of structural sound radiation in an acoustic enclosure consisting of flexible structure
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作者 陈大林 陈南 《Journal of Southeast University(English Edition)》 EI CAS 2014年第3期318-322,共5页
The active control of structural sound radiation in an acoustic enclosure is studied by using distributed point force actuators as the secondary control force, and the control mechanisms for the radiated noise in the ... The active control of structural sound radiation in an acoustic enclosure is studied by using distributed point force actuators as the secondary control force, and the control mechanisms for the radiated noise in the cavity are analyzed. A rectangular enclosure involving two simply supported flexible plates is created for this investigation. The characteristics of the primary and secondary sound field and the structural-acoustic coupled system are analyzed, and the optimal control objective for reducing the sound pressure level (SPL) in the cavity is derived. The response of the SPL in the cavity is analyzed and compared when the secondary point force actuators with different locations and parameters are applied to the two flexible plates. The results indicate that the noise in the cavity can be better controlled when some point force actuators are applied to two flexible plates for cooperative control rather than the point force actuators being only applied to the excited flexible plate. 展开更多
关键词 active control acoustic mode radiated noise control mechanism sound pressure level (SPL)
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High-efficiency prediction method for helicopter global/ground noise based on near-field acoustic holography
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作者 Mengxue SHAO Yang LU +1 位作者 Xice XU Jiaxin LU 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2024年第7期271-284,共14页
Noise reduction program design is an effective approach that relies on efficient noise prediction for reducing ground noise during flight.The existing noise prediction methods have the limitations of being computation... Noise reduction program design is an effective approach that relies on efficient noise prediction for reducing ground noise during flight.The existing noise prediction methods have the limitations of being computationally expensive or only applicable to far-fields.In this paper,a High-Efficiency Prediction Method(HEPM)for helicopter global/ground noise based on near-field acoustic holography is proposed.The HEPM can predict the global noise based on acoustic modal analysis and has the advantages of high prediction accuracy and low time cost.The process is given as follows:firstly,the rotor noise on the holographic surface in the specified flight is obtained by simulations or experiments.Secondly,the global noise model,which maps time-domain noise to acoustic modes,is established based on near-field acoustic holography and Fourier acoustic analysis methods.Finally,combined with acoustic modal amplitude,the model established enables efficiently predicting the global/ground noise in the corresponding flight state.To verify the accuracy of the prediction method,a simulation study is conducted in hovering and forward flight states using a model helicopter with a 2-meter rotor and Rotor Body Interaction(ROBIN)fuselage.The comparison of HEPM with numerical results shows that the average prediction errors of the global and ground noise are less than 0.3 dB and 0.2 dB,respectively.For a region containing 100000 observers,the computation time of the HEPM is only one-fifth of that of the acoustic hemisphere method,demonstrating the rapidity of the proposed method. 展开更多
关键词 HELICOPTER Rotor noise prediction Noise abatement procedure design acoustic modal analysis near-field acoustic holography
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Calculation on Cylinder Pressure Fluctuation by Using the Wave Equation in KIVA Program 被引量:5
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作者 WEI Haiqiao WEI Jingsi SHU Gequn 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2012年第2期362-369,共8页
Cylinder pressure fluctuation during combustion process of internal combustion engine is closely related to combustion noise and knock.The current studies are based on cylinder pressure test to obtain information on c... Cylinder pressure fluctuation during combustion process of internal combustion engine is closely related to combustion noise and knock.The current studies are based on cylinder pressure test to obtain information on combustion noise and knock,but there is little for simulation of combustion pressure fluctuation.Based on effects of combustion process in the combustion chamber on cylinder pressure by using wave equation,the mechanism of pressure fluctuation during combustion is researched with three-dimensional acoustic wave equation and flow field model of KIVA program.The cylinder pressure fluctuation curve,temperature field and acoustic field are obtained from the coupled calculation of the wave equation and KIVA program.The frequency spectrum analysis is taken with the cylinder pressure oscillation of cylinder pressure measured and calculated.The calculation result is consistent with the experimental result.This indicates that the cylinder pressure fluctuation can be correctly calculated with the wave equation.Analysis of calculation results of temperature field and acoustic field shows that sound field changes faster than flame propagates,and distribution of sound field is more complicated.Combustion pressure oscillation in the diesel engine is under highly unstable condition.This indicates that the combination of cylinder pressure fluctuation model and combustion model is an effective method to study the pressure oscillations and a new method to study the combustion noise and knock. 展开更多
关键词 COMBUSTION pressure oscillation acoustic pressure KNOCK wave equation
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