The object of research of this paper is the DSA380 high-speed pantograph.The near-field unsteady flow around the pantograph was investigated using large eddy simulation(LES)while the far-field aerodynamic noise was an...The object of research of this paper is the DSA380 high-speed pantograph.The near-field unsteady flow around the pantograph was investigated using large eddy simulation(LES)while the far-field aerodynamic noise was analysed in the frame of the Ffowcs Williams-Hawkings(FW-H)acoustic analogy.According to the results,the contact strip,base frame and knuckle are the main aerodynamic noise sources,with vortex shedding,flow separation and recombination around the pantograph being related key physical factors.The aerodynamic noise radiates outwards in the form of spherical waves when the distance of the noise receiving point is farther than 8 m.The sound pressure level(SPL)grows approximately as the 6th power of pantograph operating speed.The aerodynamic noise energy is mainly concentrated in the region of 400-1000 Hz,and the frequency band is wider with crosswind than without crosswind.The peak frequency displays a linear relationships with the operating speed and crosswind velocity,respectively.The aerodynamic and aeroacoustic generation from the knuckle-downstream orientation of the pantograph is superior to those of the knuckle-upstream orientation model.This finding may be used for the optimal design of future pantograph configurations in the presence of crosswind.展开更多
The sound generated by a NACA0012 airfoil in the wake of a rod is numerically simulated by two approaches, one is the large eddy simulation （LES） with the FW-H acoustic analogy and the other is the LES with the Powe...The sound generated by a NACA0012 airfoil in the wake of a rod is numerically simulated by two approaches, one is the large eddy simulation （LES） with the FW-H acoustic analogy and the other is the LES with the Powell vortex sound theory, in order to compare the accuracies of their predictions. The vortical structures around the rod-airfoil are computed by the LES and captured by the vortex identification （Q）. The acoustic predictions are verified by the measurements. It is shown that the computed results by the two hybrid approa- ches （LES and FW-H, LES and Powell） are very similar. Both are shown to be satisfactory in the prediction of the noise generated by an unsteady flow. Subsequently, the numerical simulations of the wall pressure fluctuations and the flow-induced noise of a NACA0015 airfoil are made by the two hybrid approaches. At two angles of attack （ 0~ and 8~ ）, the wall pressure fluctuations of the NACA0015 airfoil are computed. The obtained power spectra of the wall pressure fluctuations are analyzed and compared with the measured data. And the vortical structures around the airfoil at two angles of attack are simulated and analyzed. After that, the flow induced noises of the NACA0015 airfoil at two angles of attack are predicted by the two hybrid approaches （LES and FW-H, LES and Powell）. The radiated sound spectra are analyzed and compared with the experimental data. Comparisons show that both are robust, credible and satisfactory in the numerical prediction of the flow induced noise. All numerical simulations are carried out by parallel processing in the Wuxi supercomputing center.展开更多
The flow past various mechanical cavity, which is a common structure on the surface of the underwater vehicle, and generating hydrodynamic noise has attracted considerable attention in recent years. In this paper, a h...The flow past various mechanical cavity, which is a common structure on the surface of the underwater vehicle, and generating hydrodynamic noise has attracted considerable attention in recent years. In this paper, a hybrid method is presented to investigate the hydrodynamic noise induced by mechanical cavities with various shapes. With this method, the noise sources in the near wall turbulences or in the wake are computed by the large eddy simulation （LES） and the generation and propagation of the acoustic waves are solved by the Ffowcs Williams-Hawkings （FW-H） acoustic analogy method with acoustic source terms extracted from the time-dependent solutions of the unsteady flow. The feasibility and reliability of the current method was verified by comparing with experimental data （Wang, 2009）. The 2D cavity models with different cross-section shapes and 3D cavity models with different cavity mouth shapes （rectangular and circular） are developed to study the influence of cavity shape on the hydrodynamic noise. By comparing the flow mechanisms, wall pressure fluctuations, near-field and far-field sound propagation distributions, it is found that the quadrangular cavity with equal depths of leading-edge and trailing-edge is preferred for its inducing lower hydrodynamic noise than the cylindrical cavity does.展开更多
Varieties of research on turbulent-induced noise are conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyse efficiently and accurately. Application of FW-H acoustic ...Varieties of research on turbulent-induced noise are conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyse efficiently and accurately. Application of FW-H acoustic analogy without turbulent noise is the most popular method due to its calculation cost. In this paper, turbulent-induced noise is predicted using RANS turbulence model and permeable FW-H method. For simplicity, noise from 2D cylinder is examined using three different methods: direct method of RANS, FW-H method without turbulent noise and permeable FW-H method which can take into account of turbulent-induced noise. Turbulent noise was well predicted using permeable FW-H method with same computational cost of original FW-H method. Also, ability of permeable FW-H method to predict highly accurate turbulent-induced noise by applying adequate permeable surface is presented. The procedure to predict turbulent- induced noise using permeable FW-H is established and its usability is shown.展开更多
为探究水平管内气液两相流流型变化激励流动噪声特性,结合VOF(volume of fluid)多相流模型与Lighthill声类比理论开展数值计算研究。结果表明,随着气相和液相流速增加,气液两相流呈现弹状流–层状流–泡状流的演变规律,进而导致噪声呈...为探究水平管内气液两相流流型变化激励流动噪声特性,结合VOF(volume of fluid)多相流模型与Lighthill声类比理论开展数值计算研究。结果表明,随着气相和液相流速增加,气液两相流呈现弹状流–层状流–泡状流的演变规律,进而导致噪声呈现不同变化趋势。随着频率增加,弹状流噪声呈现先减小后增大的趋势,而层状流和泡状流噪声分别呈现逐渐减小和增大的趋势。此外,在不同工况下,泡状流诱导噪声最大,弹状流噪声次之,层状流噪声最小。研究成果对于气液两相流噪声控制技术研究具有重要指导作用。展开更多
As one of the main aerodynamic noise sources of high-speed trains, the pantograph is a complex structure containing many components, and the flow around it is extremely dynamic, with high-level turbulence. This study ...As one of the main aerodynamic noise sources of high-speed trains, the pantograph is a complex structure containing many components, and the flow around it is extremely dynamic, with high-level turbulence. This study analyzed the near-field unsteady flow around a pantograph using a large-eddy simulation(LES) with high-order finite difference schemes. The far-field aerodynamic noise from a pantograph was predicted using a computational fluid dynamics(CFD)/Ffowcs Williams-Hawkings(FW-H) acoustic analogy. The surface oscillating pressure data were also used in a boundary element method(BEM) acoustic analysis to predict the aerodynamic noise sources of a pantograph and the far-field sound radiation. The results indicated that the main aerodynamic noise sources of the pantograph were the panhead, base frame and knuckle. The panhead had the largest contribution to the far-field aerodynamic noise of the pantograph. The vortex shedding from the panhead generated tonal noise with the dominant peak corresponding to the vortex shedding frequency and the oscillating lift force exerted back on the fluid around the panhead.Additionally, the peak at the second harmonic frequency was associated with the oscillating drag force. The contribution of the knuckle-downstream direction to the pantograph aerodynamic noise was less than that of the knuckle-upstream direction of the pantograph, and the average sound pressure level(SPL) was 3.4 dBA. The directivity of the noise radiated exhibited a typical dipole pattern in which the noise directivity was obvious at the horizontal plane of θ=0°,the longitudinal plane of θ=120°,and the vertical plane of θ=90°.展开更多
基金supported in part by National Key R&D Program of China(Grant No.2016YFE0205200)High-Speed Railway Basic Research Fund Key Project of China(Grant No.U1234208)+1 种基金National Natural Science Foundation of China(Grant No.11972179,51475394)China Postdoctoral Science Foundation Grant(Grant No.2019M662201).
文摘The object of research of this paper is the DSA380 high-speed pantograph.The near-field unsteady flow around the pantograph was investigated using large eddy simulation(LES)while the far-field aerodynamic noise was analysed in the frame of the Ffowcs Williams-Hawkings(FW-H)acoustic analogy.According to the results,the contact strip,base frame and knuckle are the main aerodynamic noise sources,with vortex shedding,flow separation and recombination around the pantograph being related key physical factors.The aerodynamic noise radiates outwards in the form of spherical waves when the distance of the noise receiving point is farther than 8 m.The sound pressure level(SPL)grows approximately as the 6th power of pantograph operating speed.The aerodynamic noise energy is mainly concentrated in the region of 400-1000 Hz,and the frequency band is wider with crosswind than without crosswind.The peak frequency displays a linear relationships with the operating speed and crosswind velocity,respectively.The aerodynamic and aeroacoustic generation from the knuckle-downstream orientation of the pantograph is superior to those of the knuckle-upstream orientation model.This finding may be used for the optimal design of future pantograph configurations in the presence of crosswind.
文摘The sound generated by a NACA0012 airfoil in the wake of a rod is numerically simulated by two approaches, one is the large eddy simulation （LES） with the FW-H acoustic analogy and the other is the LES with the Powell vortex sound theory, in order to compare the accuracies of their predictions. The vortical structures around the rod-airfoil are computed by the LES and captured by the vortex identification （Q）. The acoustic predictions are verified by the measurements. It is shown that the computed results by the two hybrid approa- ches （LES and FW-H, LES and Powell） are very similar. Both are shown to be satisfactory in the prediction of the noise generated by an unsteady flow. Subsequently, the numerical simulations of the wall pressure fluctuations and the flow-induced noise of a NACA0015 airfoil are made by the two hybrid approaches. At two angles of attack （ 0~ and 8~ ）, the wall pressure fluctuations of the NACA0015 airfoil are computed. The obtained power spectra of the wall pressure fluctuations are analyzed and compared with the measured data. And the vortical structures around the airfoil at two angles of attack are simulated and analyzed. After that, the flow induced noises of the NACA0015 airfoil at two angles of attack are predicted by the two hybrid approaches （LES and FW-H, LES and Powell）. The radiated sound spectra are analyzed and compared with the experimental data. Comparisons show that both are robust, credible and satisfactory in the numerical prediction of the flow induced noise. All numerical simulations are carried out by parallel processing in the Wuxi supercomputing center.
基金supported by the Key Program of National Natural Science Foundation of China (Grant No. 50835006)the National Science and Technology Major Project of China (Grant No. 2008ZX05027-004-03)
文摘The flow past various mechanical cavity, which is a common structure on the surface of the underwater vehicle, and generating hydrodynamic noise has attracted considerable attention in recent years. In this paper, a hybrid method is presented to investigate the hydrodynamic noise induced by mechanical cavities with various shapes. With this method, the noise sources in the near wall turbulences or in the wake are computed by the large eddy simulation （LES） and the generation and propagation of the acoustic waves are solved by the Ffowcs Williams-Hawkings （FW-H） acoustic analogy method with acoustic source terms extracted from the time-dependent solutions of the unsteady flow. The feasibility and reliability of the current method was verified by comparing with experimental data （Wang, 2009）. The 2D cavity models with different cross-section shapes and 3D cavity models with different cavity mouth shapes （rectangular and circular） are developed to study the influence of cavity shape on the hydrodynamic noise. By comparing the flow mechanisms, wall pressure fluctuations, near-field and far-field sound propagation distributions, it is found that the quadrangular cavity with equal depths of leading-edge and trailing-edge is preferred for its inducing lower hydrodynamic noise than the cylindrical cavity does.
文摘Varieties of research on turbulent-induced noise are conducted with combinations of acoustic analogy methods and computational fluid dynamic methods to analyse efficiently and accurately. Application of FW-H acoustic analogy without turbulent noise is the most popular method due to its calculation cost. In this paper, turbulent-induced noise is predicted using RANS turbulence model and permeable FW-H method. For simplicity, noise from 2D cylinder is examined using three different methods: direct method of RANS, FW-H method without turbulent noise and permeable FW-H method which can take into account of turbulent-induced noise. Turbulent noise was well predicted using permeable FW-H method with same computational cost of original FW-H method. Also, ability of permeable FW-H method to predict highly accurate turbulent-induced noise by applying adequate permeable surface is presented. The procedure to predict turbulent- induced noise using permeable FW-H is established and its usability is shown.
文摘为探究水平管内气液两相流流型变化激励流动噪声特性,结合VOF(volume of fluid)多相流模型与Lighthill声类比理论开展数值计算研究。结果表明,随着气相和液相流速增加,气液两相流呈现弹状流–层状流–泡状流的演变规律,进而导致噪声呈现不同变化趋势。随着频率增加,弹状流噪声呈现先减小后增大的趋势,而层状流和泡状流噪声分别呈现逐渐减小和增大的趋势。此外,在不同工况下,泡状流诱导噪声最大,弹状流噪声次之,层状流噪声最小。研究成果对于气液两相流噪声控制技术研究具有重要指导作用。
基金supported by the High-Speed Railway Basic Research Fund Key Project of China(Grant No.U1234208)the National Key Research and Development Program of China(Grant No.2016YFB1200403)+1 种基金the National Natural Science Foundation of China(Grant Nos.51475394&51605397)the Research Project of State Key Laboratory of Traction Power(Grant No.2016TPL_T02)
文摘As one of the main aerodynamic noise sources of high-speed trains, the pantograph is a complex structure containing many components, and the flow around it is extremely dynamic, with high-level turbulence. This study analyzed the near-field unsteady flow around a pantograph using a large-eddy simulation(LES) with high-order finite difference schemes. The far-field aerodynamic noise from a pantograph was predicted using a computational fluid dynamics(CFD)/Ffowcs Williams-Hawkings(FW-H) acoustic analogy. The surface oscillating pressure data were also used in a boundary element method(BEM) acoustic analysis to predict the aerodynamic noise sources of a pantograph and the far-field sound radiation. The results indicated that the main aerodynamic noise sources of the pantograph were the panhead, base frame and knuckle. The panhead had the largest contribution to the far-field aerodynamic noise of the pantograph. The vortex shedding from the panhead generated tonal noise with the dominant peak corresponding to the vortex shedding frequency and the oscillating lift force exerted back on the fluid around the panhead.Additionally, the peak at the second harmonic frequency was associated with the oscillating drag force. The contribution of the knuckle-downstream direction to the pantograph aerodynamic noise was less than that of the knuckle-upstream direction of the pantograph, and the average sound pressure level(SPL) was 3.4 dBA. The directivity of the noise radiated exhibited a typical dipole pattern in which the noise directivity was obvious at the horizontal plane of θ=0°,the longitudinal plane of θ=120°,and the vertical plane of θ=90°.
