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Far-field sonic boom prediction considering atmospheric turbulence effects: An improved approach

Chinese Journal of Aeronautics 2022年第9期35卷 208-225页

作者： Jianling QIAO Zhonghua HAN Liwen ZHANG Wenping SONG Bifeng SONG Institute of Aerodynamic and Multidisciplinary Design Optimization School of AeronauticsNorthwestern Polytechnical UniversityXi'an 710071China National Key Laboratory of Science and Technology on Aerodynamic Design and Research School of AeronauticsNorthwestern Polytechnical UniversityXi'an710071China

Accurate prediction of sonic boom is one of key challenges for the design of a low-boom supersonic aircraft. For most of available far-field prediction methods, the effect of atmospheric turbulence appearing in the planetary boundary layer cannot be considered, which results in remarkable inaccuracy of predicting ground-level sonic boom waveform. Although some efforts have been made to overcome the shortcoming, the turbulence effects are not yet well described so far. This article proposes an improved method by extending the two-dimensional Heterogeneous One-Way Approximation for the Resolution of Diffraction(HOWARD) equation to account for the axial and transverse convections of wind fluctuation as well as the effect of temperature fluctuation. The proposed method is validated by comparing the predictions with the flight-test data of JAXA D-SEND#1 LBM, which shows that the result of the proposed method is in better agreement with the flight-test data than that of the method without considering atmospheric turbulence effects.Then, distortion mechanism of sonic boom waveforms caused by atmospheric turbulence is analyzed by using the proposed method. It is indicated that the effect of turbulent convection makes uniform sonic-boom wavefronts irregular, which creates the condition of diffraction effect to perturb waveforms. Finally, the proposed method is applied to investigate the behavior of two types of waveforms given by the sonic boom minimization theory. Results show that a far-field waveform with a weaker initial shock is more beneficial for low-boom design of a supersonic aircraft.

关键词： atmospheric turbulence Augmented Burgers equation HOWARD equation Sonic boom Supersonic transport

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Diffraction deep neural network-based classification for vector vortex beams

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Chinese Physics B 2024年第3期33卷 387-392页

作者：彭怡翔陈兵王乐赵生妹 Institute of Signal Processing and Transmission Nanjing University of Posts and Telecommunications (NJUPT)Nanjing 210003China Key Laboratory of Broadband Wireless Communication and Sensor Network Technology Ministry of EducationNanjing 210003China National Laboratory of Solid State Microstructures Nanjing UniversityNanjing 210093China

The vector vortex beam(VVB)has attracted significant attention due to its intrinsic diversity of information and has found great applications in both classical and quantum communications.However,a VVB is unavoidably affected by atmospheric turbulence(AT)when it propagates through the free-space optical communication environment,which results in detection errors at the receiver.In this paper,we propose a VVB classification scheme to detect VVBs with continuously changing polarization states under AT,where a diffractive deep neural network(DDNN)is designed and trained to classify the intensity distribution of the input distorted VVBs,and the horizontal direction of polarization of the input distorted beam is adopted as the feature for the classification through the DDNN.The numerical simulations and experimental results demonstrate that the proposed scheme has high accuracy in classification tasks.The energy distribution percentage remains above 95%from weak to medium AT,and the classification accuracy can remain above 95%for various strengths of turbulence.It has a faster convergence and better accuracy than that based on a convolutional neural network.

关键词： vector vortex beam diffractive deep neural network classification atmospheric turbulence

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Theoretical analysis of the optical rotational Doppler effect under atmospheric turbulence by mode decomposition

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Chinese Physics B 2023年第10期32卷 459-467页

作者：马圣杰徐世龙董骁张鑫源陈友龙胡以华 State Key Laboratory of Pulsed Power Laser Technology National University of Defense TechnologyHefei 230037China Key Laboratory of Electronic Restriction of Anhui Province National University of Defense TechnologyHefei 230037China

The optical rotational Doppler effect associated with orbital angular momentum provides a new means for rotational velocity detection.In this paper,we investigate the influence of atmospheric turbulence on the rotational Doppler effect.First,we deduce the generalized formula of the rotational Doppler shift in atmospheric turbulence by mode decomposition.It is found that the rotational Doppler signal frequency spectrum will be broadened,and the bandwidth is related to the turbulence intensity.In addition,as the propagation distance increases,the bandwidth also increases.And when C_(n)^(2)≤5×10^(-15)m^(-2/3)and 2z≤2 km,the rotational Doppler signal frequency spectrum width d and the spiral spectrum width d_(0)satisfy the relationship d=2d_(0-1).Finally,we analyze the influence of mode crosstalk on the rotational Doppler effect,and the results show that it destroys the symmetrical distribution of the rotational Doppler spectrum about 2l·Ω/2π.This theoretical model enables us to better understand the generation of the rotational Doppler frequency and may help us better analyze the influence of the complex atmospheric environment on the rotational Doppler frequency.

关键词： optical rotational Doppler effect atmospheric turbulence vortex beam mode decomposition mode crosstalk

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Characteristics of a partially coherent Gaussian Schell-model beam propagating in slanted atmospheric turbulence

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Chinese Physics B 2012年第5期21卷 233-240页

作者：李亚清吴振森 School of Science Xidian University

On the basis of the extended Huygens-Fresnel principle and the model of the refractive-index structure constant in the atmospheric turbulence proposed by the International Telecommunication Union-Radio Communication Sector,the characteristics of the partially coherent Gaussian Schell-model（GSM） beams propagating in slanted atmospheric turbulence are studied.Using the cross-spectral density function（CSDF）,we derive the expressions for the effective beam radius,the spreading angle,and the average intensity.The variance of the angle-of-arrival fluctuation and the wander effect of the GSM beam in the turbulence are calculated numerically.The influences of the coherence degree,the propagation distance,the propagation height,and the waist radius on the propagation characteristics of the partially coherent beams are discussed and compared with those of the fully coherent Gaussian beams.

关键词： atmospheric turbulence partially coherent beam propagation in a slanted path

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Partially coherent Gaussian–Schell model pulse beam propagation in slant atmospheric turbulence

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Chinese Physics B 2014年第6期23卷 295-303页

作者：李亚清吴振森张元元王明军 School of Physics and Optoelectronic Engineering Xidian University School of Physics and Electronic Engineering Xianyang Normal College

Based on the extended Huygens-Fresnel principle, a two-frequency, two-point cross-spectral density function of partially coherent Gaussian-Schell model pulse （GSMP） beam propagation in slant atmospheric turbulence is derived. Using the Markov approximation method and on the assumption that （w1 - w2）/（w1 ＋ w2） ≤ 1, the theory obtained is valid for turbulence of any strength and can be applied to narrow-band signals. The expressions for average beam intensity, the beam size, and the two-frequency complex degree of coherence of a GSMP beam are obtained. The numerical results are presented, and the effects of the frequency, initial pulse width, initial beam radius, zenith angle, and outer scales on the complex degree of coherence are discussed. This study provides a better understanding of the second-order statistics of a GSMP beam propagating through atmospheric turbulence in the space-frequency domain.

关键词： atmospheric propagation partial coherence atmospheric turbulence

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Propagation of the off-axis superposition of partially coherent beams through atmospheric turbulence

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Chinese Physics B 2009年第2期18卷 571-580页

作者：张恩涛季小玲吕百达 Institute of Laser Physics and Chemistry Sichuan University School of Sciences of Southwest Petroleum University College of Electronic Engineering Sichuan Normal University

The propagation properties of the off-axis superposition of partially coherent beams through atmospheric turbulence and their beam quality in terms of the mean-squared beam width w（z） and the power in the bucket （PIB） are studied in detail, where the effects of partial coherence, off-axis beam superposition and atmospheric turbulence are considered. The analytical expressions for the intensity, the beam width and the PIB are derived, and illustrative examples are given numerically. It is shown that the maximum intensity/max and the PIB decrease and w（z） increases as the refraction index structure constant Cn^2 increases. Therefore, the turbulence results in a degradation of the beam quality. However, the resulting partially coherent beam with a smaller value of spatial correlation parameter γ and larger values of separate distance Xd and beam number M is less affected by the turbulence than that with a larger value of y and smaller values of Xd and M. The main results obtained in this paper are explained physically.

关键词： off-axis superposition of partially coherent beams atmospheric turbulence propagation property beam quality

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Scintillation of partially coherent Gaussian–Schell model beam propagation in slant atmospheric turbulence considering inner- and outer-scale effects

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Chinese Physics B 2014年第7期23卷 409-416页

作者：李亚清吴振森张元元王明军 School of Physics and Optoelectronic Engineering Xidian University School of Physics and Electronic Engineering Xianyang Normal College

Based on the modified Rytov theory and the international telecommunication union-radio （ITU-R） slant atmospheric structure constant model, the uniform scintillation index of partially coherent Gaussian-Schell model （GSM） beam propa- gation in the slant path is derived from weak- to strong-turbulence regions considering inner- and outer-scale effects. The effects of wavelength of beams and inner- and outer-scale of turbulence on scintillation are analyzed numerically. Compar- ison between the scintillation of GSM beams under the von Karman spectrum and that of beams under the modified Hill spectrum is made. The results obtained show that the scintillation index obtained under the von Karman spectrum is smaller than that under the modified Hill spectrum. This study can find theory bases for the experiments of the partially coherent GSM beam propagation through atmospheric turbulence.

关键词： atmospheric turbulence partially coherent beam scintillation atmospheric propagation

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Orbital angular momentum multiplexing communication system over atmospheric turbulence with K-best detection

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Science China(Information Sciences) 2021年第9期64卷 175-186页

作者： Yingmeng GE Liang WU Chuan ZHANG Zaichen ZHANG Laboratory of Efficient Architectures for Digital-communication and Signal-processing (LEADS) Southeast University National Mobile Communications Research Laboratory Southeast University Purple Mountain Laboratories

As the optical communication technology advances, vortex beam with orbital angular momentum(OAM) has gained wide attention due to its potential to significantly increase the channel capacity. Under the influence of atmospheric turbulence, there are still challenging problems in the OAM multiplexing system. To the best of our knowledge, in this paper one multiple-input-multiple-output(MIMO) detection technology named K-best detection, is first applied to the OAM multiplexing system. Numerical simulation results indicate the proposed solution enhances the performance of the optical communication system compared with data-aided least mean square(DA-LMS) and minimum mean squared error(MMSE) detection. Furthermore,with MMSE sorted QR decomposition(MMSE-SQRD) preprocessing, the performance of K-best detection can be further improved. When Cn~2= 1×10.14, about 4.4 dB signal-to-noise ratio(SNR) gain can be obtained by preprocessing at k = 2 while the complexity is not significantly increased. Computational complexity is also analyzed in this paper, results show that K-best detection with winner path extension(WPE) algorithm can achieve 43% system complexity reduction, achieving a compromise between performance and complexity in K-best detection.

关键词： orbital angular momentum atmospheric turbulence K-best detection MMSE-SQRD preprocessing WPE algorithm

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Propagation of partially coherent beams carrying an edge dislocation through atmospheric turbulence along a slant path

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Chinese Physics B 2010年第9期19卷 647-654页

作者：李晋红张洪润吕百达 Institute of Laser Physics and Chemistry Sichuan University Department of Applied Physics Sichuan University

This paper derives the explicit expressions for the average intensity, beam width and angular spread of Gaussian Schell-model （GSM） beams with edge dislocation propagating through atmospheric turbulence along a slant path. The propagation of GSM beams with edge dislocation through horizontal atmospheric turbulence can be treated as a special case through a slant one. The propagation properties of GSM beams with edge dislocation through slant atmospheric turbulence are studied, where the influence of edge dislocation parameters including the slope p and off-axis distance d on the spreading of GSM beams with edge dislocation in atmospheric turbulence is stressed. It shows that the spreading of the intensity profile of GSM beams with edge dislocation along a slant path is smaller than that along a horizontal path in the long-distance atmospheric propagation. The larger the slope ｜p｜ and the smaller the off-axis distance ｜d｜ are, the less the beam-width spreading and angular spread of GSM beams with edge dislocation are affected by turbulence. The CSM beams with edge dislocation is less affected by turbulence than that of GSM beams without edge dislocation. The results are illustrated numerically and their validity is interpreted physically.

关键词： partially coherent beams with edge dislocation atmospheric turbulence slant path

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Progress in Natural Science:Materials International 2005年第12期15卷 1110-1116页

作者： LIU Gang,LI Xin,JIANG Weimei and LI Min Department of atmospheric Sciences,Nanjing University,Nanjing 210093,China Beijing Municipal Environmental Protection Bureau,Beijing 100044,China Department of atmospheric Sciences Nanjing University Nanjing 210093 China Beijing Municipal Environmental Protection Bureau Beijing 100044 China

The S-L (She and Leveque) scaling law,also named the hierarchical similarity theory,has been extensively tested for the turbulence made in the laboratory,but seldom been tested for the turbulence in the atmospheric boundary layer (ABL).In this paper, the S-L scaling law is applied to the turbulence in the ABL observed under unstably stratified conditions and over different types of underlying surfaces.The results of analyses show that over this type of homogeneous and flat underlying surface,such as the underlying surface in HUBEX (Huaihe River Basin Energy and Water Cycle Experiment),vertical speed and temperature fields well satisfy the S-L scaling law.For the turbulence over the homogeneous but rather rough underlying surface of forest and under unstably stratified conditions in PFRD (Park Falls Ranger District of the Chequamegon National Forest,Wisconsin,USA),the analyses show that the vertical speed and temperature fields sometimes conform sometimes do not conform to the S-L scaling law.However,at a time,either both of the vertical speed and temperature fields conform to the S-L scaling law,or both of them do not.Horizontal speed fields in both of the field experiments do not satisfy the S-L scaling law.The new explanation of the above-mentioned phenomena is given.

关键词： atmospheric turbulence Reynolds number S-L scaling law in the atmospheric turbulence boundary layer processes nonlinear dynamics

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