The potential based low order surface panel method is used to predict the hydrodynamic performance of marine propellers. In present method the hyperboloidal quadrilateral panels are employed to avoid the gap between t...The potential based low order surface panel method is used to predict the hydrodynamic performance of marine propellers. In present method the hyperboloidal quadrilateral panels are employed to avoid the gap between the panels. The influencecoefficients of panels are calculated by Morino’s analytical formulations for increasing numerically calculating speed.The pres-sure Kutta condition is satisfied on the trailing edge of propeller blade by Newton-Raphson iterative procedure.Therefore展开更多
The blade frequency noise of non-cavitation propeller in a uniform flow is analyzed in time domain. The unsteady loading (dipole source) on the blade surface is calculated by a potential-based surface panel method. ...The blade frequency noise of non-cavitation propeller in a uniform flow is analyzed in time domain. The unsteady loading (dipole source) on the blade surface is calculated by a potential-based surface panel method. Then the time- dependent pressure data is used as the input for Ffowcs Williams-Hawkings formulation to predict the acoustics pressure. The integration of noise source is performed over the true blade surface rather than the nothickness blade surface, and the effect of hub can be considered. The noise characteristics of the non-cavitation propeller and the numerical discretization forms are discussed.展开更多
Outdoor power transformers are one of the most pervasive noise sources in power transmission and distribution systems.Accurate prediction of outdoor noise propagation plays a dominant role for the evaluation and contr...Outdoor power transformers are one of the most pervasive noise sources in power transmission and distribution systems.Accurate prediction of outdoor noise propagation plays a dominant role for the evaluation and control of noise relevant to the transformer stations.In this paper surface vibration tests are carried out on a scale model of a single-phase transformer tank wall at different excitation frequencies.The phase and amplitude of test data are found to be randomly distributed when the excitation frequency exceeds the seventh mode frequency,which allows the single-phase power transformer to be simplified as incoherent point sources.An outdoor-coherent model is subsequently developed and incorporated with the image source method to investigate noise propagation from single-phase power transformers,due to the occurrence of multiple reflections and diffractions in the propagation path of each point source.The proposed model is used to calculate the sound field of the power transformer group by exploiting the additional phase information.In comparison with the ISO9613 model and the boundary element method,it is found that the proposed coherent image source method leads to more accurate prediction results,and hence better performance for the prediction of the outdoor noise induced by single-phase power transformers.展开更多
The unsteady sheet cavitation of podded propeller was predicted by using a surface panel method. The interaction between propeller and pod was treated with the iterative calculation of induced velocity potential, and ...The unsteady sheet cavitation of podded propeller was predicted by using a surface panel method. The interaction between propeller and pod was treated with the iterative calculation of induced velocity potential, and the method of induced velocity potential can save a great deal of storage and computation time compared to the method of induced velocity. The induced velocity potential of unit singularity on every pod panel to every key blade panel and of unit singularity on every key blade panel and its wake panel to every pod panel were calculated when the key blade is at every angle position. Based on the wake model of the conventional single propeller, a new wake model of podded propeller was constructed. The propeller is analyzed only on the key blade in order to save computation time and memory space. The method can be used to calculate the hydrodynamics performance and cavitation of propeller in uniform and non-uniform inflows. It can give the unsteady force and cavitation shape of propeller. The propeller cavitation range determined by the present method agrees with the observation results of cavity image given in cavitation tunnel well, and this proves the practicability of the method.展开更多
An optimal marine propeller design method is proposed,which integrates the lifting line and surface panel method and is characterized by the use of the surface panel method to take the hub effect into consideration.By...An optimal marine propeller design method is proposed,which integrates the lifting line and surface panel method and is characterized by the use of the surface panel method to take the hub effect into consideration.By developing an integrated approach instead of an iterative method for the calculation of the interaction between the hub and the designed blades,the hub effects on the optimal circulation can be accounted for throughout the theoretical design procedure.This new integrated method provides a fast and accurate enough method to model the straight forward hub surface,in the optimal propeller design.A systematic design procedure from the basic design inputs to the blade geometry determination is performed and the designed propellers are validated by the surface panel method and the RANS method.The design and analysis cases are considered by different approaches with comparison and validation.And a comparative study including different hub geometries is also performed to reveal the mechanism of the hub effect on the distributions of the propeller optimal loads.展开更多
An improved localization method consisting of "filtering-time delay estimationhyperbolic localization" is proposed. Combining the empirical mode decomposition(EMD)and time delay estimation method based on generali...An improved localization method consisting of "filtering-time delay estimationhyperbolic localization" is proposed. Combining the empirical mode decomposition(EMD)and time delay estimation method based on generalized average magnitude difference function,the original signals are decomposed into intrinsic mode function(IMF) components. The energy distribution criterion and spectrum consistency criterion are used to select the IMFs, which can represent the physical characteristics of the source signal. Several sets of signals are applied to estimate the time delay, and then a vector matching criterion is proposed to select the correct time delay estimation. Considering the hydrophones location, a shell model is established and projected to a plane according to the quadrant before the hyperbolic localization. Results of mooring and sailing tests show that the proposed method improves the localization accuracy,and reduces the error caused by time delay estimation.展开更多
This paper shows the presence of noises and technique to reduce these noises during the surface wave analysis. The frequency-dependent properties of Rayleigh-type surface waves can be used for imaging and characterizi...This paper shows the presence of noises and technique to reduce these noises during the surface wave analysis. The frequency-dependent properties of Rayleigh-type surface waves can be used for imaging and characterizing the shallow subsurface. Interference by coherent source-generated noise inhibits the reliability of shear-wave velocities determined through inversion of the phase velocities of Rayleigh waves. Among these interferences by non-planar, non-fundamental mode Rayleigh waves (noise) are body waves, scattered and non-source-generated surface waves, and highermode surface waves. For the reduction of noise, the filtering technique is implemented in this paper for the multichannel analysis of surface wave method (MASW). With the de-noising technique during the MASW method, more robust and reliable outcome is achieved. The significance of this paper is to obtain pre-awareness about noises during surface wave analysis and take better outcomes with denoising performance in near surface soil investigations.展开更多
This paper proposes a novel optimization framework in passive control techniques to reduce noise pollution.The geometries of the structures are represented by Catmull-Clark subdivision surfaces,which are able to build...This paper proposes a novel optimization framework in passive control techniques to reduce noise pollution.The geometries of the structures are represented by Catmull-Clark subdivision surfaces,which are able to build gap-free Computer-Aided Design models and meanwhile tackle the extraordinary points that are commonly encountered in geometricmodelling.The acoustic fields are simulated using the isogeometric boundary elementmethod,and a density-based topology optimization is conducted to optimize distribution of sound-absorbing materials adhered to structural surfaces.The approach enables one to perform acoustic optimization from Computer-Aided Design models directly without needingmeshing and volume parameterization,thereby avoiding the geometric errors and time-consuming preprocessing steps in conventional simulation and optimization methods.The effectiveness of the present method is demonstrated by three dimensional numerical examples.展开更多
The methods of modifying dimension and shape of structure, or covering damping material are effective to reduce structure-borne noise, while these methods are based on the knowledge of qualitative and quantitative rel...The methods of modifying dimension and shape of structure, or covering damping material are effective to reduce structure-borne noise, while these methods are based on the knowledge of qualitative and quantitative relationship between sound radiation and design parameters. In order to decrease the complexity of the problem, response surface method(RSM) was utilized to analyze and optimize the vibro-acoustic properties of the damping structure. A simple case was illustrated to demonstrate the capabilities of the developed procedure. A structure-born noise problem was approximated by a series of polynomials using RSM. Three main performances were considered, i.e. sound radiation power, first order modal frequency and total mass. Consequently, the response surface model not only gives the direction of design modification, it also leads to an optimal design of complex systems.展开更多
The blade frequency noise of a cavitating propeller in a uniform flow is analyzed in the time domain. The unsteady loading (of a dipole source) and the sheet cavity volume (of a monopole source) on the propeller s...The blade frequency noise of a cavitating propeller in a uniform flow is analyzed in the time domain. The unsteady loading (of a dipole source) and the sheet cavity volume (of a monopole source) on the propeller surface are calculated by a potential-based surface panel method. Then the time-dependent pressure and the cavity volume data are used as the input for the Fowcs Williams-Hawkings formulation to predict the acoustics pressure. The integration of the noise source is performed over the true blade surface rather than the ideal blade surface without thickness. The noise characteristics of the cavitating propeller are discussed. With the sheet cavitation, the thickness (cavitation) noise is larger than the loading noise and is the dominant noise source. The noise directivity is not as clear as that of the noise under a non-cavitation condition. The cavitation noise is attenuated more slowly than the non-cavitation noise.展开更多
声学黑洞(Acoustic Black Hole,ABH)对弯曲波的聚集效应具有宽频、高效、实现方法简单灵活等特点,在结构减振降噪领域具有广泛的应用前景。以一维声学黑洞梁为对象,结合声学黑洞半解析建模计算方法和响应面优化方法,分析声学黑洞特征长...声学黑洞(Acoustic Black Hole,ABH)对弯曲波的聚集效应具有宽频、高效、实现方法简单灵活等特点,在结构减振降噪领域具有广泛的应用前景。以一维声学黑洞梁为对象,结合声学黑洞半解析建模计算方法和响应面优化方法,分析声学黑洞特征长度、截断厚度、幂律以及阻尼层特征长度和厚度这5个参数对一维声学黑洞梁减振效果的影响规律。以一维声学黑洞梁的减振效果为优化目标,对梁和阻尼的结构参数进行优化设计,优化后的一维声学黑洞梁结构在10~8000Hz频率范围内的平均加速度级降低19.03dB。研究对一维声学黑洞梁结构在减振领域的工程应用具有参考价值。展开更多
The hydrodynamic performance of a propeller in unsteady inflow was calculated using the surface panel method. The surfaces of blades and hub were discreted by a number of hyperboloidal quadrilateral panels with consta...The hydrodynamic performance of a propeller in unsteady inflow was calculated using the surface panel method. The surfaces of blades and hub were discreted by a number of hyperboloidal quadrilateral panels with constant source and doublet distribution. Each panel's corner coordinates were calculated by spline interpolation between the main parameter and the blade geometry of the propeller. The integral equation was derived using the Green Formula. The influence coefficient of the matrix was calculated by the Morino analytic formula. The tangential velocity distribution was calculated with the Yanagizawa method, and the pressure coefficient was calculated using the Bonuli equation. The pressure Kutta condition was satisfied at the trailing edge of the propeller blade using the Newton-Raphson iterative procedure, so as to make the pressure coefficients of the suction and pressure faces of the blade equal at the trailing edge. Calculated results for the propeller in steady inflow were taken as initialization values for the unsteady inflow calculation process. Calculations were carried out from the moment the propeller achieved steady rotation. At each time interval, a linear algebraic equation combined with Kutta condition was established on a key blade and solved numerically. Comparison between calculated results and experimental results indicates that this method is correct and effective.展开更多
A doublet integral equation is formulated for the two-dimensional dissipative potential flow around a hydrofoil submerged below a free-water surface. The free-water surface is assumed to involve energy dissipation, an...A doublet integral equation is formulated for the two-dimensional dissipative potential flow around a hydrofoil submerged below a free-water surface. The free-water surface is assumed to involve energy dissipation, and thus it is the source of damping. A doublet panel method is developed from incorporation of the dissipative Green function approach and the doublet distributions on the hydrofoil surface. Numerical computations are implemented, and the derived numerical results are in good agreement with analytic solutions and experimental measurements.展开更多
This paper has predicted the range and volume of unsteady sheet cavitation of a propeller by using the surface panel method. The linearization in cavity thickness is adopted to reduce the computing time and storage sp...This paper has predicted the range and volume of unsteady sheet cavitation of a propeller by using the surface panel method. The linearization in cavity thickness is adopted to reduce the computing time and storage space. The iteration scheme between chordwise strips has been used because the range and volume of cavitation are both unknown. The propeller cavitation range determined by the calculation method presented in this paper agrees with the observation results of cavity image at cavitation tunnel very well, and this proves the practicability of the method.展开更多
文摘The potential based low order surface panel method is used to predict the hydrodynamic performance of marine propellers. In present method the hyperboloidal quadrilateral panels are employed to avoid the gap between the panels. The influencecoefficients of panels are calculated by Morino’s analytical formulations for increasing numerically calculating speed.The pres-sure Kutta condition is satisfied on the trailing edge of propeller blade by Newton-Raphson iterative procedure.Therefore
基金supported by the National Natural Science Foundation of China (Grant No. 51009145)the Research Foundation of the State Key Lab of Ocean Engineering (Grant No. 0811)+1 种基金the Research Foundation of the Ministry of Education Key Laboratory of High Speed Ship Engineering (Grant No. HSSE1004)the Natural Science Foundation of Naval University of Engineering (Grant No. HGDQNJJ10010)
文摘The blade frequency noise of non-cavitation propeller in a uniform flow is analyzed in time domain. The unsteady loading (dipole source) on the blade surface is calculated by a potential-based surface panel method. Then the time- dependent pressure data is used as the input for Ffowcs Williams-Hawkings formulation to predict the acoustics pressure. The integration of noise source is performed over the true blade surface rather than the nothickness blade surface, and the effect of hub can be considered. The noise characteristics of the non-cavitation propeller and the numerical discretization forms are discussed.
基金This work is funded by the Anhui Natural Science Foundation Project of China(under Grant KJ2016A201)the National Natural Science Foundation of China(under Grant 11774378).
文摘Outdoor power transformers are one of the most pervasive noise sources in power transmission and distribution systems.Accurate prediction of outdoor noise propagation plays a dominant role for the evaluation and control of noise relevant to the transformer stations.In this paper surface vibration tests are carried out on a scale model of a single-phase transformer tank wall at different excitation frequencies.The phase and amplitude of test data are found to be randomly distributed when the excitation frequency exceeds the seventh mode frequency,which allows the single-phase power transformer to be simplified as incoherent point sources.An outdoor-coherent model is subsequently developed and incorporated with the image source method to investigate noise propagation from single-phase power transformers,due to the occurrence of multiple reflections and diffractions in the propagation path of each point source.The proposed model is used to calculate the sound field of the power transformer group by exploiting the additional phase information.In comparison with the ISO9613 model and the boundary element method,it is found that the proposed coherent image source method leads to more accurate prediction results,and hence better performance for the prediction of the outdoor noise induced by single-phase power transformers.
基金Project supported by the Research Foundation of the Ministry of Education Key Laboratory of High Speed Ship Engineering(Grant No. HSSE0803).
文摘The unsteady sheet cavitation of podded propeller was predicted by using a surface panel method. The interaction between propeller and pod was treated with the iterative calculation of induced velocity potential, and the method of induced velocity potential can save a great deal of storage and computation time compared to the method of induced velocity. The induced velocity potential of unit singularity on every pod panel to every key blade panel and of unit singularity on every key blade panel and its wake panel to every pod panel were calculated when the key blade is at every angle position. Based on the wake model of the conventional single propeller, a new wake model of podded propeller was constructed. The propeller is analyzed only on the key blade in order to save computation time and memory space. The method can be used to calculate the hydrodynamics performance and cavitation of propeller in uniform and non-uniform inflows. It can give the unsteady force and cavitation shape of propeller. The propeller cavitation range determined by the present method agrees with the observation results of cavity image given in cavitation tunnel well, and this proves the practicability of the method.
文摘An optimal marine propeller design method is proposed,which integrates the lifting line and surface panel method and is characterized by the use of the surface panel method to take the hub effect into consideration.By developing an integrated approach instead of an iterative method for the calculation of the interaction between the hub and the designed blades,the hub effects on the optimal circulation can be accounted for throughout the theoretical design procedure.This new integrated method provides a fast and accurate enough method to model the straight forward hub surface,in the optimal propeller design.A systematic design procedure from the basic design inputs to the blade geometry determination is performed and the designed propellers are validated by the surface panel method and the RANS method.The design and analysis cases are considered by different approaches with comparison and validation.And a comparative study including different hub geometries is also performed to reveal the mechanism of the hub effect on the distributions of the propeller optimal loads.
基金supported by the National Natural Science Foundation of China(51209214)the Research Development Foundation of Naval University of Engineering(425517K031)
文摘An improved localization method consisting of "filtering-time delay estimationhyperbolic localization" is proposed. Combining the empirical mode decomposition(EMD)and time delay estimation method based on generalized average magnitude difference function,the original signals are decomposed into intrinsic mode function(IMF) components. The energy distribution criterion and spectrum consistency criterion are used to select the IMFs, which can represent the physical characteristics of the source signal. Several sets of signals are applied to estimate the time delay, and then a vector matching criterion is proposed to select the correct time delay estimation. Considering the hydrophones location, a shell model is established and projected to a plane according to the quadrant before the hyperbolic localization. Results of mooring and sailing tests show that the proposed method improves the localization accuracy,and reduces the error caused by time delay estimation.
基金supported by Research Project of Science Fund No. 01-01-02-SF0338Science Fund No.01-01-02-SF0681 from Ministry of Science, Technologyand Innovation of Malaysia
文摘This paper shows the presence of noises and technique to reduce these noises during the surface wave analysis. The frequency-dependent properties of Rayleigh-type surface waves can be used for imaging and characterizing the shallow subsurface. Interference by coherent source-generated noise inhibits the reliability of shear-wave velocities determined through inversion of the phase velocities of Rayleigh waves. Among these interferences by non-planar, non-fundamental mode Rayleigh waves (noise) are body waves, scattered and non-source-generated surface waves, and highermode surface waves. For the reduction of noise, the filtering technique is implemented in this paper for the multichannel analysis of surface wave method (MASW). With the de-noising technique during the MASW method, more robust and reliable outcome is achieved. The significance of this paper is to obtain pre-awareness about noises during surface wave analysis and take better outcomes with denoising performance in near surface soil investigations.
基金We acknowledge the support of the National Natural Science Foundation of China(NSFC)under Grant Nos.51904202 and 11702238Stephane Bordas thanks the financial support of Intuitive modeling and SIMulation platform(IntuiSIM)(PoC17/12253887)grant by Luxembourg National Research Fund.
文摘This paper proposes a novel optimization framework in passive control techniques to reduce noise pollution.The geometries of the structures are represented by Catmull-Clark subdivision surfaces,which are able to build gap-free Computer-Aided Design models and meanwhile tackle the extraordinary points that are commonly encountered in geometricmodelling.The acoustic fields are simulated using the isogeometric boundary elementmethod,and a density-based topology optimization is conducted to optimize distribution of sound-absorbing materials adhered to structural surfaces.The approach enables one to perform acoustic optimization from Computer-Aided Design models directly without needingmeshing and volume parameterization,thereby avoiding the geometric errors and time-consuming preprocessing steps in conventional simulation and optimization methods.The effectiveness of the present method is demonstrated by three dimensional numerical examples.
文摘The methods of modifying dimension and shape of structure, or covering damping material are effective to reduce structure-borne noise, while these methods are based on the knowledge of qualitative and quantitative relationship between sound radiation and design parameters. In order to decrease the complexity of the problem, response surface method(RSM) was utilized to analyze and optimize the vibro-acoustic properties of the damping structure. A simple case was illustrated to demonstrate the capabilities of the developed procedure. A structure-born noise problem was approximated by a series of polynomials using RSM. Three main performances were considered, i.e. sound radiation power, first order modal frequency and total mass. Consequently, the response surface model not only gives the direction of design modification, it also leads to an optimal design of complex systems.
基金supported by the National Natural Science Foundation of China(Grant No.51009145)supported by the Research Foundation of the State Key Laboratory of Ocean Engineering,Shanghai Jiao Tong University(Grant Nos.0811,0904)the Research of Ministry of Education,Key Laboratory of High Speed Ship Engineering,Wuhan University of Technology(Grant No.HSSE1004)
文摘The blade frequency noise of a cavitating propeller in a uniform flow is analyzed in the time domain. The unsteady loading (of a dipole source) and the sheet cavity volume (of a monopole source) on the propeller surface are calculated by a potential-based surface panel method. Then the time-dependent pressure and the cavity volume data are used as the input for the Fowcs Williams-Hawkings formulation to predict the acoustics pressure. The integration of the noise source is performed over the true blade surface rather than the ideal blade surface without thickness. The noise characteristics of the cavitating propeller are discussed. With the sheet cavitation, the thickness (cavitation) noise is larger than the loading noise and is the dominant noise source. The noise directivity is not as clear as that of the noise under a non-cavitation condition. The cavitation noise is attenuated more slowly than the non-cavitation noise.
文摘声学黑洞(Acoustic Black Hole,ABH)对弯曲波的聚集效应具有宽频、高效、实现方法简单灵活等特点,在结构减振降噪领域具有广泛的应用前景。以一维声学黑洞梁为对象,结合声学黑洞半解析建模计算方法和响应面优化方法,分析声学黑洞特征长度、截断厚度、幂律以及阻尼层特征长度和厚度这5个参数对一维声学黑洞梁减振效果的影响规律。以一维声学黑洞梁的减振效果为优化目标,对梁和阻尼的结构参数进行优化设计,优化后的一维声学黑洞梁结构在10~8000Hz频率范围内的平均加速度级降低19.03dB。研究对一维声学黑洞梁结构在减振领域的工程应用具有参考价值。
基金Supported by the Doctoral Program of Higher Education Foundation under Grant No. 2006021702.
文摘The hydrodynamic performance of a propeller in unsteady inflow was calculated using the surface panel method. The surfaces of blades and hub were discreted by a number of hyperboloidal quadrilateral panels with constant source and doublet distribution. Each panel's corner coordinates were calculated by spline interpolation between the main parameter and the blade geometry of the propeller. The integral equation was derived using the Green Formula. The influence coefficient of the matrix was calculated by the Morino analytic formula. The tangential velocity distribution was calculated with the Yanagizawa method, and the pressure coefficient was calculated using the Bonuli equation. The pressure Kutta condition was satisfied at the trailing edge of the propeller blade using the Newton-Raphson iterative procedure, so as to make the pressure coefficients of the suction and pressure faces of the blade equal at the trailing edge. Calculated results for the propeller in steady inflow were taken as initialization values for the unsteady inflow calculation process. Calculations were carried out from the moment the propeller achieved steady rotation. At each time interval, a linear algebraic equation combined with Kutta condition was established on a key blade and solved numerically. Comparison between calculated results and experimental results indicates that this method is correct and effective.
文摘A doublet integral equation is formulated for the two-dimensional dissipative potential flow around a hydrofoil submerged below a free-water surface. The free-water surface is assumed to involve energy dissipation, and thus it is the source of damping. A doublet panel method is developed from incorporation of the dissipative Green function approach and the doublet distributions on the hydrofoil surface. Numerical computations are implemented, and the derived numerical results are in good agreement with analytic solutions and experimental measurements.
文摘This paper has predicted the range and volume of unsteady sheet cavitation of a propeller by using the surface panel method. The linearization in cavity thickness is adopted to reduce the computing time and storage space. The iteration scheme between chordwise strips has been used because the range and volume of cavitation are both unknown. The propeller cavitation range determined by the calculation method presented in this paper agrees with the observation results of cavity image at cavitation tunnel very well, and this proves the practicability of the method.