2017 Vol. 12, No. 4
2017, 12(4): .
Abstract:
[1] Scientific consciousness: an important dimension in ship innovation…WU Chongjian(1)[2] Structural and acoustic response due to excitation from ship stern: overview and suggestions for future research…HUA Hongxing, YU Qiang(6)[3] Active noise control technique and its application on ships…CHEN Kean(17)[4] Application of system concept in vibration and noise reduction…SHENG Meiping, WANG Minqing, LI Qiaojiao(22)[5] Design and optimization of sound package using FE-SEA numerical reverberation method…YANG Deqing, SHI Jiaxin, YU Yang(26)[6] Acoustic performance design and optimal allocation of sound package in ship cabin noise reduction…YANG Deqing, XU Zixuan, GAO Chu(35)[7] Damping layout optimization for ship's cabin noise reduction based on statistical energy analysis…WU Weiguo, WEI Jiezheng, LIN Yongshui, et al(41)[8] Acoustic design method of ship's cabin based on geometrical acoustics…FENG Aijing, WEI Qiang, ZHANG Dahai(49)[9] Low-noise hydraulic power unit design based on vibration modal and transfer function analysis…SUN Yinghui, LI Zhiyin, LI Jia, et al(55)[10] Analytical research of vibration and far-field acoustic radiation of cylindrical shell immersed at finite depth…GUO Wenjie, LI Tianyun, ZHU Xiang, et al(62)[11] Numerical calculation of acoustic radiation from band-vibrating structures via FEM/FAQP method…GAO Honglin, LI Sheng(71)[12] Numerical method for calculating sound radiation characteristics of plate structure excited by turbulent boundary layer…LI Zuhui, CHEN Meixia(76)[13] Prediction of waterjet excited underwater radiated noise by boundary element method…LIU Qiang, WANG Yongsheng, ZHANG Mingyu, et al(83)[14] Accuracy verification and analysis of SEA method for calculating radiation noise pressure of submerged cylindrical shell…ZHANG Kai, JI Gang, ZHOU Qidou, et al(89)[15] Vibration analysis of multi-span beam system under arbitrary boundary and coupling conditions…ZHENG Chaofan, WU Xiaoguang, ZHANG Cheng(95)[16] Free vibration characteristics analysis of rectangular plate with rectangular opening based on Fourier series method …WANG Minhao, LI Kai, QIU Yongkang, et al(102)[17] Calculation method for natural vibration frequency of stern cabin in oceanographic research vessel…LIU Xi'an, WU Guangming, LI Weijie(110)[18] Experiments of opening and cavity shear flow-induced vibration and structural coupling resonance…XIONG Jishi, LV Shijin, QIU Changlin, et al(117)[19] Experimental research into active control of low-frequency line spectral disturbances in liquid-filled pipe…SUN Yunping, SUN Hongling, ZHANG Wei, et al(122)[20] Measurement method of reverberation field reciprocity parameter…SUN Jundong, SHANG Dajing, SUN Xiaoyue(128)[21] Measurement and analysis of self-noise in hybrid-driven underwater gliders…LIU Lu, XIAO Ling(132)[22] Research and application of abnormal noise source positioning experiment based on double cylindrical shell…LI Ruibiao, XU Rongwu, CUI Lilin, et al(140)[23] Near-field and high-resolution cylindrical noise source location method based on vector sound pressure array…ZUO Xiang, CHEN Huan(147)
[1] Scientific consciousness: an important dimension in ship innovation…WU Chongjian(1)[2] Structural and acoustic response due to excitation from ship stern: overview and suggestions for future research…HUA Hongxing, YU Qiang(6)[3] Active noise control technique and its application on ships…CHEN Kean(17)[4] Application of system concept in vibration and noise reduction…SHENG Meiping, WANG Minqing, LI Qiaojiao(22)[5] Design and optimization of sound package using FE-SEA numerical reverberation method…YANG Deqing, SHI Jiaxin, YU Yang(26)[6] Acoustic performance design and optimal allocation of sound package in ship cabin noise reduction…YANG Deqing, XU Zixuan, GAO Chu(35)[7] Damping layout optimization for ship's cabin noise reduction based on statistical energy analysis…WU Weiguo, WEI Jiezheng, LIN Yongshui, et al(41)[8] Acoustic design method of ship's cabin based on geometrical acoustics…FENG Aijing, WEI Qiang, ZHANG Dahai(49)[9] Low-noise hydraulic power unit design based on vibration modal and transfer function analysis…SUN Yinghui, LI Zhiyin, LI Jia, et al(55)[10] Analytical research of vibration and far-field acoustic radiation of cylindrical shell immersed at finite depth…GUO Wenjie, LI Tianyun, ZHU Xiang, et al(62)[11] Numerical calculation of acoustic radiation from band-vibrating structures via FEM/FAQP method…GAO Honglin, LI Sheng(71)[12] Numerical method for calculating sound radiation characteristics of plate structure excited by turbulent boundary layer…LI Zuhui, CHEN Meixia(76)[13] Prediction of waterjet excited underwater radiated noise by boundary element method…LIU Qiang, WANG Yongsheng, ZHANG Mingyu, et al(83)[14] Accuracy verification and analysis of SEA method for calculating radiation noise pressure of submerged cylindrical shell…ZHANG Kai, JI Gang, ZHOU Qidou, et al(89)[15] Vibration analysis of multi-span beam system under arbitrary boundary and coupling conditions…ZHENG Chaofan, WU Xiaoguang, ZHANG Cheng(95)[16] Free vibration characteristics analysis of rectangular plate with rectangular opening based on Fourier series method …WANG Minhao, LI Kai, QIU Yongkang, et al(102)[17] Calculation method for natural vibration frequency of stern cabin in oceanographic research vessel…LIU Xi'an, WU Guangming, LI Weijie(110)[18] Experiments of opening and cavity shear flow-induced vibration and structural coupling resonance…XIONG Jishi, LV Shijin, QIU Changlin, et al(117)[19] Experimental research into active control of low-frequency line spectral disturbances in liquid-filled pipe…SUN Yunping, SUN Hongling, ZHANG Wei, et al(122)[20] Measurement method of reverberation field reciprocity parameter…SUN Jundong, SHANG Dajing, SUN Xiaoyue(128)[21] Measurement and analysis of self-noise in hybrid-driven underwater gliders…LIU Lu, XIAO Ling(132)[22] Research and application of abnormal noise source positioning experiment based on double cylindrical shell…LI Ruibiao, XU Rongwu, CUI Lilin, et al(140)[23] Near-field and high-resolution cylindrical noise source location method based on vector sound pressure array…ZUO Xiang, CHEN Huan(147)
2017, 12(4): 1-5.
doi: 10.3969/j.issn.1673-3185.2017.04.001
Abstract:
Innovation features huge uncertainties and risks. According to statistics, less than one percent of discoveries and inventions convert successfully into innovations and real applications. The key element in converting innovative ideas into applications is the scientific consciousness of the innovators, which is very important for such open, complex and large-scale system engineering as naval architecture. Due to the lack of early warning for the cognition of dimension, many innovative ideas fail to convert into successful applications. Thus, enhancing scientific consciousness is important for holding the general interest and forming an integral vision of innovation so as to lead innovative design to the correct roads and approaches, and control risks in advance.
Innovation features huge uncertainties and risks. According to statistics, less than one percent of discoveries and inventions convert successfully into innovations and real applications. The key element in converting innovative ideas into applications is the scientific consciousness of the innovators, which is very important for such open, complex and large-scale system engineering as naval architecture. Due to the lack of early warning for the cognition of dimension, many innovative ideas fail to convert into successful applications. Thus, enhancing scientific consciousness is important for holding the general interest and forming an integral vision of innovation so as to lead innovative design to the correct roads and approaches, and control risks in advance.
2017, 12(4): 6-16.
doi: 10.3969/j.issn.1673-3185.2017.04.002
Abstract:
Several decades after the development of acoustic stealth technology for ships, there remains an urgent necessity to reduce low frequency structural and acoustic response due to excitation from the stern. This paper reviews research into the coupled vibration and acoustic problems of the sterns of vessels. Attention is especially paid to three key aspects: the characteristics of propeller forces, the vibration-acoustic signatures of coupled propeller-shaft-hull systems, and vibration/noise controls. Therefore, the mapping relationships of vibration noise from the stern excitation and propeller-shaft-hull system is obtained, and the control approaches for low frequency vibration noise is presented. Thereafter, several suggestions are made for further research work in the testing technology of the unsteady force of propellers, the structural vibration induced by the stern bearing friction and the vibration control of propeller-shaft systems in the future.
Several decades after the development of acoustic stealth technology for ships, there remains an urgent necessity to reduce low frequency structural and acoustic response due to excitation from the stern. This paper reviews research into the coupled vibration and acoustic problems of the sterns of vessels. Attention is especially paid to three key aspects: the characteristics of propeller forces, the vibration-acoustic signatures of coupled propeller-shaft-hull systems, and vibration/noise controls. Therefore, the mapping relationships of vibration noise from the stern excitation and propeller-shaft-hull system is obtained, and the control approaches for low frequency vibration noise is presented. Thereafter, several suggestions are made for further research work in the testing technology of the unsteady force of propellers, the structural vibration induced by the stern bearing friction and the vibration control of propeller-shaft systems in the future.
2017, 12(4): 17-21, 34.
doi: 10.3969/j.issn.1673-3185.2017.04.003
Abstract:
Due to the rapid development during past three decades, Active Noise Control(ANC) has become a highly complementary noise control approach in comparison with traditional approaches, and has formed a complete system including basic theory, investigation approach, key techniques and system implementation. Meanwhile, substantial progress has been achieved in such fields as the practical application, industrialization development and commercial popularization of ANC, and this developed technique provides a practical and feasible choice for the active control of ship noise. In this review paper, its sound field analysis, system setup and key techniques are summarized, typical examples of ANC-based engineering applications including control of cabin noise and duct noise are briefly described, and a variety of forefronts and problems associated with the applications of ANC in ship noise control, such as active sound absorption, active sound insulation and smart acoustic structure, are subsequently discussed.
Due to the rapid development during past three decades, Active Noise Control(ANC) has become a highly complementary noise control approach in comparison with traditional approaches, and has formed a complete system including basic theory, investigation approach, key techniques and system implementation. Meanwhile, substantial progress has been achieved in such fields as the practical application, industrialization development and commercial popularization of ANC, and this developed technique provides a practical and feasible choice for the active control of ship noise. In this review paper, its sound field analysis, system setup and key techniques are summarized, typical examples of ANC-based engineering applications including control of cabin noise and duct noise are briefly described, and a variety of forefronts and problems associated with the applications of ANC in ship noise control, such as active sound absorption, active sound insulation and smart acoustic structure, are subsequently discussed.
2017, 12(4): 22-25.
doi: 10.3969/j.issn.1673-3185.2017.04.004
Abstract:
Although certain vibration and noise control technologies are maturing, such as vibration absorption, vibration isolation, sound absorption and sound insulation, and new methods for specific frequency bands or special environments have been proposed unceasingly, there is still no guarantee that practical effective vibration and noise reduction can be obtained. An important constraint for vibration and noise reduction is the lack of a system concept, and the integrity and relevance of such practical systems as ship structure have not obtained enough attention. We have tried to use the system engineering theory in guiding vibration and noise reduction, and have already achieved certain effects. Based on the system concept, the noise control of a petroleum pipeline production workshop has been completed satisfactorily, and the abnormal noise source identification of an airplane has been accomplished successfully. We want to share our experience and suggestions to promote the popularization of the system engineering theory in vibration and noise control.
Although certain vibration and noise control technologies are maturing, such as vibration absorption, vibration isolation, sound absorption and sound insulation, and new methods for specific frequency bands or special environments have been proposed unceasingly, there is still no guarantee that practical effective vibration and noise reduction can be obtained. An important constraint for vibration and noise reduction is the lack of a system concept, and the integrity and relevance of such practical systems as ship structure have not obtained enough attention. We have tried to use the system engineering theory in guiding vibration and noise reduction, and have already achieved certain effects. Based on the system concept, the noise control of a petroleum pipeline production workshop has been completed satisfactorily, and the abnormal noise source identification of an airplane has been accomplished successfully. We want to share our experience and suggestions to promote the popularization of the system engineering theory in vibration and noise control.
2017, 12(4): 26-34.
doi: 10.3969/j.issn.1673-3185.2017.04.005
Abstract:
To solve the low efficiency problem of the conventional sound package, the FE-SEA numerical reverberation method is applied in the design and optimization of sound packages in the whole frequency domain. Two types of sound package with and without air layers are designed and optimized. The FE-SEA numerical reverberation method is used to calculate sound transmission loss. The thicknesses of the air layers of the sound packages are defined as design variables. The optimization results reveal that the sound package with air layer has better acoustic performance than the one without air layers, and the sound transmission loss can be raised 2-6 dB after optimization. The research results have important guiding values for ship sound package design in actual engineering.
To solve the low efficiency problem of the conventional sound package, the FE-SEA numerical reverberation method is applied in the design and optimization of sound packages in the whole frequency domain. Two types of sound package with and without air layers are designed and optimized. The FE-SEA numerical reverberation method is used to calculate sound transmission loss. The thicknesses of the air layers of the sound packages are defined as design variables. The optimization results reveal that the sound package with air layer has better acoustic performance than the one without air layers, and the sound transmission loss can be raised 2-6 dB after optimization. The research results have important guiding values for ship sound package design in actual engineering.
2017, 12(4): 35-40, 54.
doi: 10.3969/j.issn.1673-3185.2017.04.006
Abstract:
The sound package in noise reduction design of ship cabins has become the main approach for the future. The sound package is a specially designed acoustic component consisting of damping materials, absorption materials, sound isolation materials and base structural materials which can achieve the prescribed performance of noise reduction. Based on the Statistical Energy Analysis(SEA)method, quick evaluation and design methods, and the optimal allocation theory of sound packages are investigated. The standard numerical acoustic performance evaluation model, sound package optimization design model and sound package optimal allocation model are presented. A genetic algorithm is applied to solve the presented optimization problems. Design examples demonstrate the validity and efficiency of the proposed models and solutions. The presented theory and methods benefit the standardization and programming of sound package design, and decrease noise reduction costs.
The sound package in noise reduction design of ship cabins has become the main approach for the future. The sound package is a specially designed acoustic component consisting of damping materials, absorption materials, sound isolation materials and base structural materials which can achieve the prescribed performance of noise reduction. Based on the Statistical Energy Analysis(SEA)method, quick evaluation and design methods, and the optimal allocation theory of sound packages are investigated. The standard numerical acoustic performance evaluation model, sound package optimization design model and sound package optimal allocation model are presented. A genetic algorithm is applied to solve the presented optimization problems. Design examples demonstrate the validity and efficiency of the proposed models and solutions. The presented theory and methods benefit the standardization and programming of sound package design, and decrease noise reduction costs.
2017, 12(4): 41-48.
doi: 10.3969/j.issn.1673-3185.2017.04.007
Abstract:
An optimization analysis study concerning the damping control of ship's cabin noise was carried out in order to improve the effect and reduce the weight of damping. Based on the Statistical Energy Analysis (SEA) method, a theoretical deduction and numerical analysis of the first-order sensitivity analysis of the A-weighted sound pressure level concerning the damping loss factor of the subsystem were carried out. On this basis, a mathematical optimization model was proposed and an optimization program developed. Next, the secondary development of VA One software was implemented through the use of MATLAB, while the cabin noise damping control layout optimization system was established. Finally, the optimization model of the ship was constructed and numerical experiments of damping control optimization conducted. The damping installation region was divided into five parts with different damping thicknesses. The total weight of damping was set as an objective function and the A-weighted sound pressure level of the target cabin was set as a constraint condition. The best damping thickness was obtained through the optimization program, and the total damping weight was reduced by 60.4%. The results show that the damping noise reduction effect of unit weight is significantly improved through the optimization method. This research successfully solves the installation position and thickness selection problems in the acoustic design of damping control, providing a reliable analysis method and guidance for the design.
An optimization analysis study concerning the damping control of ship's cabin noise was carried out in order to improve the effect and reduce the weight of damping. Based on the Statistical Energy Analysis (SEA) method, a theoretical deduction and numerical analysis of the first-order sensitivity analysis of the A-weighted sound pressure level concerning the damping loss factor of the subsystem were carried out. On this basis, a mathematical optimization model was proposed and an optimization program developed. Next, the secondary development of VA One software was implemented through the use of MATLAB, while the cabin noise damping control layout optimization system was established. Finally, the optimization model of the ship was constructed and numerical experiments of damping control optimization conducted. The damping installation region was divided into five parts with different damping thicknesses. The total weight of damping was set as an objective function and the A-weighted sound pressure level of the target cabin was set as a constraint condition. The best damping thickness was obtained through the optimization program, and the total damping weight was reduced by 60.4%. The results show that the damping noise reduction effect of unit weight is significantly improved through the optimization method. This research successfully solves the installation position and thickness selection problems in the acoustic design of damping control, providing a reliable analysis method and guidance for the design.
2017, 12(4): 49-54.
doi: 10.3969/j.issn.1673-3185.2017.04.008
Abstract:
In light of the question of how to select the best noise control position and measures in the large noise transmission path of the cabins of a ship, based on the acoustic ray-tracing method in the theory of geometrical acoustics, and by considering the effect of the sound transmission of the bulkhead, this paper proposes the sound line search method. It is used to calculate the sound pressure of a ship's cabin, allowing the sound field distribution of multiple compartments to be simulated. The paper proposes a sound ray-searching method in which the acoustic sensitivity of different positions of the bulkhead to the noise of the target cabin is calculated by searching for the sound ray passing the target cabin. According to this, a cabin noise reduction plan can be designed to optimize medium and high frequency cabin noise. With this method, the noise of a typical cabin can be optimized and reduced by 7.3 dB. Through comparative analysis with the statistical energy method, it is proven that the method is feasible and can guide the refined design of noise reduction in ships' cabins.
In light of the question of how to select the best noise control position and measures in the large noise transmission path of the cabins of a ship, based on the acoustic ray-tracing method in the theory of geometrical acoustics, and by considering the effect of the sound transmission of the bulkhead, this paper proposes the sound line search method. It is used to calculate the sound pressure of a ship's cabin, allowing the sound field distribution of multiple compartments to be simulated. The paper proposes a sound ray-searching method in which the acoustic sensitivity of different positions of the bulkhead to the noise of the target cabin is calculated by searching for the sound ray passing the target cabin. According to this, a cabin noise reduction plan can be designed to optimize medium and high frequency cabin noise. With this method, the noise of a typical cabin can be optimized and reduced by 7.3 dB. Through comparative analysis with the statistical energy method, it is proven that the method is feasible and can guide the refined design of noise reduction in ships' cabins.
2017, 12(4): 55-61.
doi: 10.3969/j.issn.1673-3185.2017.04.009
Abstract:
The hydraulic power unit is the power source of a hydraulic system, and also the source causing hydraulic system vibration and noise. In order to further reduce the vibration and noise level of hydraulic systems, this paper presents a low-noise hydraulic station design method based on modal analysis and Vibration Transfer Function(VTF) analysis. The finite element model of the hydraulic station is established, the mode of the oil station solved and the modal superposition method used to optimize the structure of the station and the installation position of the hydraulic pump. The optimal structure of the station and the improved installation location of the pump are obtained. The VTF is used to optimize the structure of the oil tank, and the influence of the pump vibration on the station is further reduced. The test results for vibration and noise show that the design method is effective in significantly reducing the vibration and noise of the hydraulic station. The vibration acceleration of the hydraulic station is reduced by 5.7 dB, and the air noise is reduced by 2 dB. In short, this paper provides a better way for reducing the vibration and noise of hydraulic systems.
The hydraulic power unit is the power source of a hydraulic system, and also the source causing hydraulic system vibration and noise. In order to further reduce the vibration and noise level of hydraulic systems, this paper presents a low-noise hydraulic station design method based on modal analysis and Vibration Transfer Function(VTF) analysis. The finite element model of the hydraulic station is established, the mode of the oil station solved and the modal superposition method used to optimize the structure of the station and the installation position of the hydraulic pump. The optimal structure of the station and the improved installation location of the pump are obtained. The VTF is used to optimize the structure of the oil tank, and the influence of the pump vibration on the station is further reduced. The test results for vibration and noise show that the design method is effective in significantly reducing the vibration and noise of the hydraulic station. The vibration acceleration of the hydraulic station is reduced by 5.7 dB, and the air noise is reduced by 2 dB. In short, this paper provides a better way for reducing the vibration and noise of hydraulic systems.
2017, 12(4): 62-70.
doi: 10.3969/j.issn.1673-3185.2017.04.010
Abstract:
Aiming at the current lack of analytical research concerning the cylindrical shell-flow field coupling vibration and sound radiation system under the influence of a free surface, this paper proposes an analytical method which solves the vibration response and far-field acoustic radiation of a finite cylindrical shell immersed at a finite depth. Based on the image method and Graf addition theorem, the analytical expression of the fluid velocity potential can be obtained, then combined with the energy functional of the variation method to deduce the shell-liquid coupling vibration equation, which can in turn solve the forced vibration response. The research shows that, compared with an infinite fluid, a free surface can increase at the same order of resonance frequency; but as the depth of immersion gradually increases, the mean square vibration velocity tends to become the same as that in an infinite fluid. Compared with numerical results from Nastran software, this shows that the present method is accurate and reliable, and has such advantages as a simple method and a small amount of calculation. The far-field radiated pressure can be obtained by the vibration response using the Fourier transformation and stationary phase method. The results indicate that the directivity and volatility of the far-field acoustic pressure of a cylindrical shell is similar to that of an acoustical dipole due to the free surface. However, the far-field acoustic pressure is very different from the vibration characteristics, and will not tend to an infinite fluid as the submerging depth increases. Compared with the numerical method, the method in this paper is simpler and has a higher computational efficiency. It enables the far-field acoustic radiation of an underwater cylindrical shell to be predicted quickly under the influence of external incentives and the free surface, providing guiding significance for acoustic research into the half space structure vibration problem.
Aiming at the current lack of analytical research concerning the cylindrical shell-flow field coupling vibration and sound radiation system under the influence of a free surface, this paper proposes an analytical method which solves the vibration response and far-field acoustic radiation of a finite cylindrical shell immersed at a finite depth. Based on the image method and Graf addition theorem, the analytical expression of the fluid velocity potential can be obtained, then combined with the energy functional of the variation method to deduce the shell-liquid coupling vibration equation, which can in turn solve the forced vibration response. The research shows that, compared with an infinite fluid, a free surface can increase at the same order of resonance frequency; but as the depth of immersion gradually increases, the mean square vibration velocity tends to become the same as that in an infinite fluid. Compared with numerical results from Nastran software, this shows that the present method is accurate and reliable, and has such advantages as a simple method and a small amount of calculation. The far-field radiated pressure can be obtained by the vibration response using the Fourier transformation and stationary phase method. The results indicate that the directivity and volatility of the far-field acoustic pressure of a cylindrical shell is similar to that of an acoustical dipole due to the free surface. However, the far-field acoustic pressure is very different from the vibration characteristics, and will not tend to an infinite fluid as the submerging depth increases. Compared with the numerical method, the method in this paper is simpler and has a higher computational efficiency. It enables the far-field acoustic radiation of an underwater cylindrical shell to be predicted quickly under the influence of external incentives and the free surface, providing guiding significance for acoustic research into the half space structure vibration problem.
2017, 12(4): 71-75, 82.
doi: 10.3969/j.issn.1673-3185.2017.04.011
Abstract:
The Finite Element Method (FEM) combined with the Frequency Averaged Quadratic Pressure method (FAQP) are used to calculate the acoustic radiation of structures excited in the frequency band. The surface particle velocity of stiffened cylindrical shells under frequency band excitation is calculated using finite element software, the normal vibration velocity is converted from the surface particle velocity to calculate the average energy source (frequency averaged across intensity, frequency averaged across pressure and frequency averaged across velocity), and the FAQP method is used to calculate the average sound pressure level within the bandwidth. The average sound pressure levels are then compared with the bandwidth using finite element and boundary element software, and the results show that FEM combined with FAQP is more suitable for high frequencies and can be used to calculate the average sound pressure level in the 1/3 octave band with good stability, presenting an alternative to applying frequency-by-frequency calculation and the average frequency process. The FEM/FAQP method can be used as a prediction method for calculating acoustic radiation while taking the randomness of vibration at medium and high frequencies into consideration.
The Finite Element Method (FEM) combined with the Frequency Averaged Quadratic Pressure method (FAQP) are used to calculate the acoustic radiation of structures excited in the frequency band. The surface particle velocity of stiffened cylindrical shells under frequency band excitation is calculated using finite element software, the normal vibration velocity is converted from the surface particle velocity to calculate the average energy source (frequency averaged across intensity, frequency averaged across pressure and frequency averaged across velocity), and the FAQP method is used to calculate the average sound pressure level within the bandwidth. The average sound pressure levels are then compared with the bandwidth using finite element and boundary element software, and the results show that FEM combined with FAQP is more suitable for high frequencies and can be used to calculate the average sound pressure level in the 1/3 octave band with good stability, presenting an alternative to applying frequency-by-frequency calculation and the average frequency process. The FEM/FAQP method can be used as a prediction method for calculating acoustic radiation while taking the randomness of vibration at medium and high frequencies into consideration.
2017, 12(4): 76-82.
doi: 10.3969/j.issn.1673-3185.2017.04.012
Abstract:
As the turbulent boundary layer (TBL) is one of the most important sources of vibration and noise in underwater vehicles, there is an important significance in studying the numerical method for the calculation of flow-induced noise. In this paper, the methods of Principal Component Analysis (PCA) and Vibro-Acoustic Transfer Vectors (VATV) based on LMS Virtual Lab software are used to calculate the sound characteristics of a plate structure excited by TBL. The Corcos model of the wave number-frequency spectrum of the wall pressure field beneath the TBL is used to describe random excitation. By comparing the calculating time and sound pressure auto power spectra curves of the two methods, the following conclusions are obtained: both the VATV method and PCA method can be used effectively for the calculation of the flow-induced noise of structures excited by the TBL, and the results of the two methods match; the VATV method can quickly forecast the structure of flow-induced noise and takes up fewer computing resources than the PCA method; the PCA method can also obtain the structure vibration response in comparison with the VATV method. The current work can serve as a reference for the rapid prediction of the flow-induced noise of underwater structures.
As the turbulent boundary layer (TBL) is one of the most important sources of vibration and noise in underwater vehicles, there is an important significance in studying the numerical method for the calculation of flow-induced noise. In this paper, the methods of Principal Component Analysis (PCA) and Vibro-Acoustic Transfer Vectors (VATV) based on LMS Virtual Lab software are used to calculate the sound characteristics of a plate structure excited by TBL. The Corcos model of the wave number-frequency spectrum of the wall pressure field beneath the TBL is used to describe random excitation. By comparing the calculating time and sound pressure auto power spectra curves of the two methods, the following conclusions are obtained: both the VATV method and PCA method can be used effectively for the calculation of the flow-induced noise of structures excited by the TBL, and the results of the two methods match; the VATV method can quickly forecast the structure of flow-induced noise and takes up fewer computing resources than the PCA method; the PCA method can also obtain the structure vibration response in comparison with the VATV method. The current work can serve as a reference for the rapid prediction of the flow-induced noise of underwater structures.
2017, 12(4): 83-88.
doi: 10.3969/j.issn.1673-3185.2017.04.013
Abstract:
Aiming to mitigate impact of the uncertain boundary conditions setting on the underwater radiated noise calculation, the numerical prediction method of calculating the underwater radiated noise of a waterjet by the one-step boundary element method was explored. First, the transient flow field of the waterjet was calculated on the basis of Detached Eddy Simulation(DES), and the pressure fluctuations were transformed to the pulsant source with computational acoustic software. Next, taking the pulsant source as the radiant source, the underwater radiated noise of the waterjet was numerically predicted by the one-step boundary element method. The results show that the underwater radiated noise of a waterjet can be obtained by using the one-step boundary element method, which gives a more procise prodiction.
Aiming to mitigate impact of the uncertain boundary conditions setting on the underwater radiated noise calculation, the numerical prediction method of calculating the underwater radiated noise of a waterjet by the one-step boundary element method was explored. First, the transient flow field of the waterjet was calculated on the basis of Detached Eddy Simulation(DES), and the pressure fluctuations were transformed to the pulsant source with computational acoustic software. Next, taking the pulsant source as the radiant source, the underwater radiated noise of the waterjet was numerically predicted by the one-step boundary element method. The results show that the underwater radiated noise of a waterjet can be obtained by using the one-step boundary element method, which gives a more procise prodiction.
2017, 12(4): 89-94.
doi: 10.3969/j.issn.1673-3185.2017.04.014
Abstract:
Statistical Energy Analysis(SEA)is an effective method for solving high frequency structural vibration and acoustic radiation problems. When we use it to analyze submerged structures, it is necessary to consider the actions of fluid as'heavy fluid' relative to structures, which differs from when it is used in the air. The simple model of a submerged cylindrical shell is used to calculate at a higher frequency using FEM/BEM. The SEA and FEM method are then used to calculate the radiation sound pressure level, verifying the accuracy of the SEA prediction for submerged structures. The classified method of subsystems and the effect of the error of the internal loss factor on the accuracy of the results are explored. The calculated results of SEA and FEM/BEM are very different below 400 Hz, and basically the same above 400 Hz. The error caused by the division of different subsystems is about 5 dB. The error in the calculation results caused by the error of the internal loss factor is 2-3 dB. It is possible to use SEA to calculate the radiated noise of an underwater cylindrical shell when the modal density is high enough.For the cylindrical shell, dividing the subsystems along the circumference is not reliable at a low frequency, as it may lead to inaccurate calculation results. At a high frequency, it is more accurate to divide the subsystems along the circumference than the axle. For subsystems with high energy, the internal loss factor has a greater effect on the simulation results, so a more accurate way should be taken to determine the internal loss factor of subsystems with high energy.
Statistical Energy Analysis(SEA)is an effective method for solving high frequency structural vibration and acoustic radiation problems. When we use it to analyze submerged structures, it is necessary to consider the actions of fluid as'heavy fluid' relative to structures, which differs from when it is used in the air. The simple model of a submerged cylindrical shell is used to calculate at a higher frequency using FEM/BEM. The SEA and FEM method are then used to calculate the radiation sound pressure level, verifying the accuracy of the SEA prediction for submerged structures. The classified method of subsystems and the effect of the error of the internal loss factor on the accuracy of the results are explored. The calculated results of SEA and FEM/BEM are very different below 400 Hz, and basically the same above 400 Hz. The error caused by the division of different subsystems is about 5 dB. The error in the calculation results caused by the error of the internal loss factor is 2-3 dB. It is possible to use SEA to calculate the radiated noise of an underwater cylindrical shell when the modal density is high enough.For the cylindrical shell, dividing the subsystems along the circumference is not reliable at a low frequency, as it may lead to inaccurate calculation results. At a high frequency, it is more accurate to divide the subsystems along the circumference than the axle. For subsystems with high energy, the internal loss factor has a greater effect on the simulation results, so a more accurate way should be taken to determine the internal loss factor of subsystems with high energy.
2017, 12(4): 95-101.
doi: 10.3969/j.issn.1673-3185.2017.04.015
Abstract:
In order to overcome the difficulties of studying the vibration analysis model of a multi-span beam system under various boundary and coupling conditions, this paper constructs a free vibration analysis model of a multi-span beam system on the basis of the Bernoulli-Euler beam theory. The vibration characteristics of a multi-span beam system under arbitrary boundary supports and elastic coupling conditions are investigated using the current analysis model. Unlike most existing techniques, the beam displacement function is generally sought as an improved Fourier cosine series, and four sine terms are introduced to overcome all the relevant discontinuities or jumps of elastic boundary conditions. On this basis, the unknown series coefficients of the displacement function are treated as the generalized coordinates and solved using the Rayleigh-Ritz method, and the vibration problem of multi-span bean systems is converted into a standard eigenvalue problem concerning the unknown displacement expansion coefficient. By comparing the free vibration characteristics of the proposed method with those of the FEA method, the efficiency and accuracy of the present method are validated, providing a reliable and theoretical basis for multi-span beam system structure in engineering applications.
In order to overcome the difficulties of studying the vibration analysis model of a multi-span beam system under various boundary and coupling conditions, this paper constructs a free vibration analysis model of a multi-span beam system on the basis of the Bernoulli-Euler beam theory. The vibration characteristics of a multi-span beam system under arbitrary boundary supports and elastic coupling conditions are investigated using the current analysis model. Unlike most existing techniques, the beam displacement function is generally sought as an improved Fourier cosine series, and four sine terms are introduced to overcome all the relevant discontinuities or jumps of elastic boundary conditions. On this basis, the unknown series coefficients of the displacement function are treated as the generalized coordinates and solved using the Rayleigh-Ritz method, and the vibration problem of multi-span bean systems is converted into a standard eigenvalue problem concerning the unknown displacement expansion coefficient. By comparing the free vibration characteristics of the proposed method with those of the FEA method, the efficiency and accuracy of the present method are validated, providing a reliable and theoretical basis for multi-span beam system structure in engineering applications.
2017, 12(4): 102-109.
doi: 10.3969/j.issn.1673-3185.2017.04.016
Abstract:
Plate structures with openings are common in many engineering structures. The study of the vibration characteristics of such structures is directly related to the vibration reduction, noise reduction and stability analysis of an overall structure. This paper conducts research into the free vibration characteristics of a thin elastic plate with a rectangular opening parallel to the plate in an arbitrary position. We use the improved Fourier series to represent the displacement tolerance function of the rectangular plate with an opening. We can divide the plate into an eight zone plate to simplify the calculation. We then use linear springs, which are uniformly distributed along the boundary, to simulate the classical boundary conditions and the boundary conditions of the boundaries between the regions. According to the energy functional and variational method, we can obtain the overall energy functional. We can also obtain the generalized eigenvalue matrix equation by studying the extremum of the unknown improved Fourier series expansion coefficients. We can then obtain the natural frequencies and corresponding vibration modes of the rectangular plate with an opening by solving the equation. We then compare the calculated results with the finite element method to verify the accuracy and effectiveness of the method proposed in this paper. Finally, we research the influence of the boundary condition, opening size and opening position on the vibration characteristics of a plate with an opening. This provides a theoretical reference for practical engineering application.
Plate structures with openings are common in many engineering structures. The study of the vibration characteristics of such structures is directly related to the vibration reduction, noise reduction and stability analysis of an overall structure. This paper conducts research into the free vibration characteristics of a thin elastic plate with a rectangular opening parallel to the plate in an arbitrary position. We use the improved Fourier series to represent the displacement tolerance function of the rectangular plate with an opening. We can divide the plate into an eight zone plate to simplify the calculation. We then use linear springs, which are uniformly distributed along the boundary, to simulate the classical boundary conditions and the boundary conditions of the boundaries between the regions. According to the energy functional and variational method, we can obtain the overall energy functional. We can also obtain the generalized eigenvalue matrix equation by studying the extremum of the unknown improved Fourier series expansion coefficients. We can then obtain the natural frequencies and corresponding vibration modes of the rectangular plate with an opening by solving the equation. We then compare the calculated results with the finite element method to verify the accuracy and effectiveness of the method proposed in this paper. Finally, we research the influence of the boundary condition, opening size and opening position on the vibration characteristics of a plate with an opening. This provides a theoretical reference for practical engineering application.
2017, 12(4): 110-116.
doi: 10.3969/j.issn.1673-3185.2017.04.017
Abstract:
Vibration prediction for stern cabins is an important part of research into the global vibration of ships. To address the need to improve precision and efficiency, a study is carried out on the proportion of a mixed model and the length of a 3D stern cabin model to investigate the natural frequency of a ship. Using the FE method, different types of model are established for a research vessel, including six mixed models that are used for the basis of a detailed discussion on the different proportions of mixed models, and five stern cabin models that are used to analyze the impact of the modeling range on the natural frequency. Moreover, the Lewis method and virtual mass method are both used to consider the impact of outside water in the analysis of the wet mode. It is observed that the results of the calculated natural frequency of the mixed models are approximately the same when the proportion of the mixed models is over 1/5 the length of the ship, and in good agreement with the results of the calculations when the modeling range of the stern cabin models is exactly in the vicinity of the vibration node of the ship. For the local vibration calculation of ships using the Lewis method and virtual mass method, the results of various schemes differ greatly when applied to the stern cabin models. The results suggest that the proportion of local cabin models should be 1/4 the length of the ship in the natural frequency calculation, and the virtual mass method is recommended for considering the impact of local additional water mass.
Vibration prediction for stern cabins is an important part of research into the global vibration of ships. To address the need to improve precision and efficiency, a study is carried out on the proportion of a mixed model and the length of a 3D stern cabin model to investigate the natural frequency of a ship. Using the FE method, different types of model are established for a research vessel, including six mixed models that are used for the basis of a detailed discussion on the different proportions of mixed models, and five stern cabin models that are used to analyze the impact of the modeling range on the natural frequency. Moreover, the Lewis method and virtual mass method are both used to consider the impact of outside water in the analysis of the wet mode. It is observed that the results of the calculated natural frequency of the mixed models are approximately the same when the proportion of the mixed models is over 1/5 the length of the ship, and in good agreement with the results of the calculations when the modeling range of the stern cabin models is exactly in the vicinity of the vibration node of the ship. For the local vibration calculation of ships using the Lewis method and virtual mass method, the results of various schemes differ greatly when applied to the stern cabin models. The results suggest that the proportion of local cabin models should be 1/4 the length of the ship in the natural frequency calculation, and the virtual mass method is recommended for considering the impact of local additional water mass.
2017, 12(4): 117-121.
doi: 10.3969/j.issn.1673-3185.2017.04.018
Abstract:
In order to discuss opening and cavity shear flow-induced vibration and structural coupling resonance, experiments of opening and cavity shear flow-induced vibration and structural noise control are carried out. The impact of the opening size, flow velocity and cavity thickness on shear oscillation noise, self-noise in the cavity and radiated noise are analyzed. The results show that the empirical formula of the opening shear oscillation in air is also applicable to the condition underwater, which the shear oscillation and amplitude of modal frequencies are directly proportional to the flow velocity; in case that no coupling resonance occurs, the thickness of the cavity wall will bring slight influence on the amplitude of the shear oscillation, but not on the mode frequencies; also the coupling of shear oscillatory mode and cavity wall mode show dramatic coupling resonance under certain conditions, and leads to self-noise and acoustic radiation. The findings supply useful exploration and technical support concerning the application of opening and cavity structural noise control measures.
In order to discuss opening and cavity shear flow-induced vibration and structural coupling resonance, experiments of opening and cavity shear flow-induced vibration and structural noise control are carried out. The impact of the opening size, flow velocity and cavity thickness on shear oscillation noise, self-noise in the cavity and radiated noise are analyzed. The results show that the empirical formula of the opening shear oscillation in air is also applicable to the condition underwater, which the shear oscillation and amplitude of modal frequencies are directly proportional to the flow velocity; in case that no coupling resonance occurs, the thickness of the cavity wall will bring slight influence on the amplitude of the shear oscillation, but not on the mode frequencies; also the coupling of shear oscillatory mode and cavity wall mode show dramatic coupling resonance under certain conditions, and leads to self-noise and acoustic radiation. The findings supply useful exploration and technical support concerning the application of opening and cavity structural noise control measures.
2017, 12(4): 122-127, 131.
doi: 10.3969/j.issn.1673-3185.2017.04.019
Abstract:
Noise radiation through the liquid-filled pipe system is the focus of noise control in the pipe systems of ships, while low-frequency line spectral disturbances with high energy need to be further suppressed. An Active Noise Control (ANC) system adapted to liquid-filled pipes is designed to attenuate low-frequency line spectral disturbances. This system is made up of the secondary source, controller, power amplifier, sensor etc. The system uses a frequency tracking algorithm to estimate the frequencies of noise, and a complex LMS algorithm to design the controller. A pump water circulation pipe system is implemented to validate the control system's performance in noise reduction through experiments. Active control experiments on noise sources with fixed frequency, sweeping frequency and multi-frequency are carried out respectively. The results show that the control system can track frequencies automatically, and effectively reduce the noise radiating from the pipe in cases of fixed frequency, sweeping frequency and multi-frequency. The ANC system can achieve noise attenuation of over 8 dB at multi-frequencies in liquid-filled pipes, and has good robustness. This provides a possible solution for the noise control of low-frequency line spectral disturbances in the pipe systems of ships.
Noise radiation through the liquid-filled pipe system is the focus of noise control in the pipe systems of ships, while low-frequency line spectral disturbances with high energy need to be further suppressed. An Active Noise Control (ANC) system adapted to liquid-filled pipes is designed to attenuate low-frequency line spectral disturbances. This system is made up of the secondary source, controller, power amplifier, sensor etc. The system uses a frequency tracking algorithm to estimate the frequencies of noise, and a complex LMS algorithm to design the controller. A pump water circulation pipe system is implemented to validate the control system's performance in noise reduction through experiments. Active control experiments on noise sources with fixed frequency, sweeping frequency and multi-frequency are carried out respectively. The results show that the control system can track frequencies automatically, and effectively reduce the noise radiating from the pipe in cases of fixed frequency, sweeping frequency and multi-frequency. The ANC system can achieve noise attenuation of over 8 dB at multi-frequencies in liquid-filled pipes, and has good robustness. This provides a possible solution for the noise control of low-frequency line spectral disturbances in the pipe systems of ships.
2017, 12(4): 128-131.
doi: 10.3969/j.issn.1673-3185.2017.04.020
Abstract:
This paper presents a method for measuring the reciprocity parameter based on the free field. It is able to achieve accurate measurement of the reverberation constant in a narrow band. The method uses the same transmitting and receiving system, and keeps the same set of parameters to measure the open circuit voltage output under different frequencies in a free field. The open circuit output voltage is measured through average technology in the reverberation control region, then the reverberation radius is calculated and the reciprocity constant obtained. This method uses a single frequency signal and the spatial averaging technique. It is simple, convenient and not suitable for complex measuring instruments. The validity of the method is verified by comparing the measured results with the reverberation time measurement.
This paper presents a method for measuring the reciprocity parameter based on the free field. It is able to achieve accurate measurement of the reverberation constant in a narrow band. The method uses the same transmitting and receiving system, and keeps the same set of parameters to measure the open circuit voltage output under different frequencies in a free field. The open circuit output voltage is measured through average technology in the reverberation control region, then the reverberation radius is calculated and the reciprocity constant obtained. This method uses a single frequency signal and the spatial averaging technique. It is simple, convenient and not suitable for complex measuring instruments. The validity of the method is verified by comparing the measured results with the reverberation time measurement.
2017, 12(4): 132-139.
doi: 10.3969/j.issn.1673-3185.2017.04.021
Abstract:
The Hybrid-driven Underwater Glider (HUG) is a new type of submersible vehicle which combines the functions of traditional Autonomous Underwater Vehicles(AUV)and Autonomous Underwater Gliders(AUG). In order to study its noise source distribution and basic self-noise characteristics, a self-noise acquisition system based on the HUG was designed and developed, and a noise analysis test carried out in a free-field pool. In August 2016, the sea trial of the Petrel Ⅱ glider was conducted in the South China Sea, with observation data at a depth range of 1 000 m as the research object. The self-noise data of the glider platform under different working conditions was obtained through the step-by-step operation method. The experimental analysis and results show that the self-noise acquisition system is stable. The contribution of mechanical noise to self-noise is greatest when the glider works in the gliding mode, while the self-noise band above 500 Hz is closely related to the work of the buoyancy adjustment unit, and peaks at 1 kHz. According to the analysis of the basic characteristics of self-noise, this provides some guidance for the implementation of vibration and noise reduction.
The Hybrid-driven Underwater Glider (HUG) is a new type of submersible vehicle which combines the functions of traditional Autonomous Underwater Vehicles(AUV)and Autonomous Underwater Gliders(AUG). In order to study its noise source distribution and basic self-noise characteristics, a self-noise acquisition system based on the HUG was designed and developed, and a noise analysis test carried out in a free-field pool. In August 2016, the sea trial of the Petrel Ⅱ glider was conducted in the South China Sea, with observation data at a depth range of 1 000 m as the research object. The self-noise data of the glider platform under different working conditions was obtained through the step-by-step operation method. The experimental analysis and results show that the self-noise acquisition system is stable. The contribution of mechanical noise to self-noise is greatest when the glider works in the gliding mode, while the self-noise band above 500 Hz is closely related to the work of the buoyancy adjustment unit, and peaks at 1 kHz. According to the analysis of the basic characteristics of self-noise, this provides some guidance for the implementation of vibration and noise reduction.
2017, 12(4): 140-146.
doi: 10.3969/j.issn.1673-3185.2017.04.022
Abstract:
Aiming at the problem of frequent abnormal outboard noise in ships, an abnormal noise source location method is proposed, and a location model checked by the double cylindrical shell experiment is built. The model calculates the coordinates through the improved hyperbolic positioning method on the basis of the traditional hyperbolic positioning method, with the time-delay estimation by the generalized cross-correlation method as the input. In the process of the experiment, the outboard abnormal noise source is simulated by the percussion, comparing the positioning accuracy of the two methods and analyzing the influence of time-delay estimation on positioning accuracy. The results show that the hyperbolic positioning method based on double cylindrical shell can accurately locate the coordinates of abnormal noise sources, and is feasible for the abnormal outboard noise source positioning of ships. In addition, the method can provide theoretical guidance for the location of abnormal outboard noise sources.
Aiming at the problem of frequent abnormal outboard noise in ships, an abnormal noise source location method is proposed, and a location model checked by the double cylindrical shell experiment is built. The model calculates the coordinates through the improved hyperbolic positioning method on the basis of the traditional hyperbolic positioning method, with the time-delay estimation by the generalized cross-correlation method as the input. In the process of the experiment, the outboard abnormal noise source is simulated by the percussion, comparing the positioning accuracy of the two methods and analyzing the influence of time-delay estimation on positioning accuracy. The results show that the hyperbolic positioning method based on double cylindrical shell can accurately locate the coordinates of abnormal noise sources, and is feasible for the abnormal outboard noise source positioning of ships. In addition, the method can provide theoretical guidance for the location of abnormal outboard noise sources.
2017, 12(4): 147-150.
doi: 10.3969/j.issn.1673-3185.2017.04.023
Abstract:
The existing underwater noise source near-field location method usually assumes that the measurement plane is flat, which increases the difficulty of applying the underwater noise target test for cylindrical distribution. Simultaneously, the conventional near-field focused beam has a lower spatial resolution when used to locate an underwater noise source with cylindrical distribution. Moreover, the near-field underwater noise source location method based on the sound pressure array has a left and right side fuzzy problem. In order to solve these problems, by establishing the near-field measurement model of the noise source with cylindrical distribution as the measurement surface, and combining the unilateral directivity of the vector hydrophone and the high resolution characteristics of the MUSIC algorithm, a near-field and high resolution location method is proposed for cylindrical distribution based on vector sound pressure, and a computer simulation is carried out. The results show that the method can use a smaller array aperture to locate the underwater noise source, enabling it to be used to locate and recognize the noise sources of complex and large-scale cylindrical systems.
The existing underwater noise source near-field location method usually assumes that the measurement plane is flat, which increases the difficulty of applying the underwater noise target test for cylindrical distribution. Simultaneously, the conventional near-field focused beam has a lower spatial resolution when used to locate an underwater noise source with cylindrical distribution. Moreover, the near-field underwater noise source location method based on the sound pressure array has a left and right side fuzzy problem. In order to solve these problems, by establishing the near-field measurement model of the noise source with cylindrical distribution as the measurement surface, and combining the unilateral directivity of the vector hydrophone and the high resolution characteristics of the MUSIC algorithm, a near-field and high resolution location method is proposed for cylindrical distribution based on vector sound pressure, and a computer simulation is carried out. The results show that the method can use a smaller array aperture to locate the underwater noise source, enabling it to be used to locate and recognize the noise sources of complex and large-scale cylindrical systems.
