The elimination of transverse wavevectors during the propagation of electromagnetic waves is highly desirable because this would have a wide range of applications in probing,imaging,and communication.In this research,...The elimination of transverse wavevectors during the propagation of electromagnetic waves is highly desirable because this would have a wide range of applications in probing,imaging,and communication.In this research,we propose and experimentally demonstrate a simple method to suppress transverse wavevectors by using coherent wave combinations.Using theoretical analysis and numerical simulation,we show that transverse wavevectors can be greatly suppressed during propagation.For further verification,we perform experiments with light waves to realize coherently combined beams;our experimental results are in good agreement with the simulated results.More importantly,we generate pin-like optical beams using this method,and pin-like optical beams exhibit superior propagation behavior over conventional Gaussian beams in turbulent fluids.展开更多
Following the wall pressure spectrum of the turbulent boundary layer developed by Corcos, a method in the frequency-wavenumber space was presented to analyze the flow noise in the vector hydrophone towed linear array....Following the wall pressure spectrum of the turbulent boundary layer developed by Corcos, a method in the frequency-wavenumber space was presented to analyze the flow noise in the vector hydrophone towed linear array. The general forms of the acoustic pressure and particle velocity in the flow noise field were obtained, and the spatial correlations of the flow noise were calculated. The numerical analysis results based on wavenumber integration show that： （1） The spatial correlations of flow noise drops rapidly with increasing axial separation between the elements, so the flow noise received by different vector hydrophones usually sampled in a half-wavelength rate can be considered as independent; （2） The flow noise is highly correlated in the radial direction at low frequency, and only those of high frequency componet can be neglected.展开更多
文摘The elimination of transverse wavevectors during the propagation of electromagnetic waves is highly desirable because this would have a wide range of applications in probing,imaging,and communication.In this research,we propose and experimentally demonstrate a simple method to suppress transverse wavevectors by using coherent wave combinations.Using theoretical analysis and numerical simulation,we show that transverse wavevectors can be greatly suppressed during propagation.For further verification,we perform experiments with light waves to realize coherently combined beams;our experimental results are in good agreement with the simulated results.More importantly,we generate pin-like optical beams using this method,and pin-like optical beams exhibit superior propagation behavior over conventional Gaussian beams in turbulent fluids.
基金the National Natural Science Foundation of China(60532040)the National Safty Basic Research Program of China(613660201,513210Z8T22)the Institute Foundation(GS08SJJ09)
文摘Following the wall pressure spectrum of the turbulent boundary layer developed by Corcos, a method in the frequency-wavenumber space was presented to analyze the flow noise in the vector hydrophone towed linear array. The general forms of the acoustic pressure and particle velocity in the flow noise field were obtained, and the spatial correlations of the flow noise were calculated. The numerical analysis results based on wavenumber integration show that： （1） The spatial correlations of flow noise drops rapidly with increasing axial separation between the elements, so the flow noise received by different vector hydrophones usually sampled in a half-wavelength rate can be considered as independent; （2） The flow noise is highly correlated in the radial direction at low frequency, and only those of high frequency componet can be neglected.
