Restoration of phase aberrations is crucial for addressing atmospheric turbulence in light propagation.Traditional restoration algorithms based on Zernike polynomials(ZPs)often encounter challenges related to high com...Restoration of phase aberrations is crucial for addressing atmospheric turbulence in light propagation.Traditional restoration algorithms based on Zernike polynomials(ZPs)often encounter challenges related to high computational complexity and insufficient capture of high-frequency phase aberration components,so we proposed a Principal-Component-Analysis-based method for representing phase aberrations.This paper discusses the factors influencing the accuracy of restoration,mainly including the sample space size and the sampling interval of D/r_(0),on the basis of characterizing phase aberrations by Principal Components(PCs).The experimental results show that a larger D/r_(0)sampling interval can ensure the generalization ability and robustness of the principal components in the case of a limited amount of original data,which can help to achieve high-precision deployment of the model in practical applications quickly.In the environment with relatively strong turbulence in the test set of D/r_(0)=24,the use of 34 terms of PCs can improve the corrected Strehl ratio(SR)from 0.007 to 0.1585,while the Strehl ratio of the light spot after restoration using 34 terms of ZPs is only 0.0215,demonstrating almost no correction effect.The results indicate that PCs can serve as a better alternative in representing and restoring the characteristics of atmospheric turbulence induced phase aberrations.These findings pave the way to use PCs of phase aberrations with fewer terms than traditional ZPs to achieve data dimensionality reduction,and offer a reference to accelerate and stabilize the model and deep learning based adaptive optics correction.展开更多
Atmospheric turbulence is an important parameter affecting laser atmospheric transmission.This paper reports on a self-developed atmospheric turbulence detection Li DAR system(scanning differential image motion Li DAR...Atmospheric turbulence is an important parameter affecting laser atmospheric transmission.This paper reports on a self-developed atmospheric turbulence detection Li DAR system(scanning differential image motion Li DAR(DIM-Li DAR)system).By designing and simulating the optical system of atmospheric turbulence detection Li DAR,the basic optical imaging accuracy has been determined.展开更多
This study evaluates the accuracy of large-eddy simulation(LES)analyses using a commonly used subgrid-scale(SGS)model based on the eddy viscosity hypothesis.The evaluation is performed by examining the Reynolds number...This study evaluates the accuracy of large-eddy simulation(LES)analyses using a commonly used subgrid-scale(SGS)model based on the eddy viscosity hypothesis.The evaluation is performed by examining the Reynolds number dependence of turbulence maintained by anisotropic and isotropic forcing techniques derived from Tay-lor analytical solutions.The Smagorinsky model,the Vreman model,and the coherent structure model are used as SGS models.LES outcomes were evaluated against those produced by direct numerical simulation(DNS).In contrast to the results with isotropic forcing,the turbulent kinetic energy of anisotropic forcing-induced tur-bulence,as calculated by DNS,exhibits a minimum in the intermediate Reynolds number range.However,all three LES analyses fail to reproduce this minimum and instead show overestimated values.This discrepancy is attributed to reduced spatial inhomogeneity of the turbulent diffusion,pressure diffusion,and pressure-strain correlation terms in the transport equations of the velocity fluctuation intensities in this Reynolds number range.Visualization results for the LES and DNS analyses further show that within this range,LES analyses reproduce two-dimensional tubular flow structures that are not observed in DNS results.展开更多
Numerical simulations were conducted on a 10-blade Sevik rotor ingesting wake downstream of two turbulence-generating grids.These simulations were based on implicit large-eddy simulation(ILES)and the boundary data imm...Numerical simulations were conducted on a 10-blade Sevik rotor ingesting wake downstream of two turbulence-generating grids.These simulations were based on implicit large-eddy simulation(ILES)and the boundary data immersion method(BDIM)for compressible flows,which were solved using a fully self-programmed Fortran code.Results show that the predicted thrust spectrum aligns closely with the experimental measurements.In addition,it captures the thrust dipole directivity of the noise around the rotating propeller due to random pressure pulsations on the blades,as well as the flow structures simultaneously.Furthermore,the differences in the statistical characteristics,flow structures,and low-frequency broadband thrust spectra due to different turbulence levels were investigated.This analysis indicates that the interaction between the upstream,which is characterized by a lower turbulence level and a higher turbulent length of scale,and the rotating propeller results in a lower amplitude in force spectra and a slight increase in the scale of tip vortices.展开更多
While Metaheuristic optimization techniques are known to work well for clustering and large-scale numerical optimization,algorithms in this category suffer from issues like reinforcement stagnation and poor late-stage...While Metaheuristic optimization techniques are known to work well for clustering and large-scale numerical optimization,algorithms in this category suffer from issues like reinforcement stagnation and poor late-stage refinement.In this paper,we propose the Improved Geyser-Inspired Optimization Algorithm(IGIOA),an enhancement of the Geyser-Inspired Optimization Algorithm(GIOA),which integrates two primary components:the Adaptive Turbulence Operator(ATO)and the Dynamic Pressure Equilibrium Operator(DPEO).ATO allows IGIOA to periodically disrupt stagnation and explore different regions by using turbulence,while DPEO ensures refinement in later iterations by adaptively modulating convergence pressure.We implemented IGIOA on 23 benchmark functions with both unimodal and multimodal contours,in addition to eight problems pertaining to cluster analysis at the UCI.IGIOA,out of all the tested methods,was able to converge most accurately while also achieving a stable convergence rate.The mitigation of premature convergence and low-level exploitation was made possible by the turbulence and pressure-based refinements.The findings from the tests confirm that the adaptation of baseline strategies by IGIOA helps deal with complex data distributions more effectively.However,additional hyperparameters which add complexity are introduced,along with increased computational cost.These include automatic tuning of parameters,ensemble or parallel variations,and hybridization with dedicated local search strategies to extend the reach of IGIOA for general optimization while also specializing it for clustering focused tasks and applications.展开更多
Due to the arid and sandy surface of the Taklimakan Desert(TD)in China,the turbulence structure and vertical distribution of ozone exhibit unique and complex characteristics.However,few studies have focused on these i...Due to the arid and sandy surface of the Taklimakan Desert(TD)in China,the turbulence structure and vertical distribution of ozone exhibit unique and complex characteristics.However,few studies have focused on these issues.To reveal the variation characteristics of summertime atmospheric turbulence and ozone concentration over the TD,we conducted joint detection experiments in July 2016 and July 2021 at Tazhong in the hinterland of the TD using an eddy covariance detection system,a GPS(Global Positioning System)sounding system,and a meteorological gradient tower.Using methods such as statistical analysis,nonlinear fitting,and Fast Fourier Transform,this study analyzed and processed parameters including temperature,relative humidity,wind speed,turbulence parameters,turbulence spectra,and ozone concentration.The high average temperature is accompanied by low relative humidity over the TD,showing a negative correlation between the two.The temperature of the 10.0-cm-deep sand layer lags the near-surface air temperature by nearly 4 h.From 09:30 to 21:00(Beijing Time),under conditions where the sensible heat flux is positive but stability parameter(z/L,where z is the height and L is the Obukhov length)is negative,the atmosphere is heated by the land surface,with the occurrence of unstable stratification;however,the conditions are the opposite(sensible heat flux is negative and z/L is positive)after 22:00,which are accompanied with the cooling of the surface radiation,occurrence of temperature inversion in the lower atmosphere,and stable stratification.A positive correlation is identified between the diurnal variation of turbulent kinetic energy(TKE)and the atmospheric boundary layer(ABL)height,with significant contributions from both the buoyancy and shear terms during the daytime.Under unstable stratification,the normalized standard deviations of the three-dimensional wind speed,temperature,and humidity conform to the Monin-Obukhov Similarity Theory(MOST).As the stability parameter z/L transitions from strongly unstable to strongly stable,the energy of the dimensionless turbulent velocity spectra gradually decreases and conforms to the -2/3 power law within the inertial subrange.In the hinterland of the TD,the summertime tropospheric ozone concentration remains below approximately 0.70×10^(-6)(volume concentration).Above the troposphere,within the range of 16,500.0-30,000.0 m,a significant increasing trend is identified in the ozone concentration with altitude.At an altitude of 30,000.0 m,the maximum ozone concentration can reach up to 7.50×10^(-6).The research findings provide both theoretical and data foundations for future in-depth studies of turbulent motion and ozone concentration distribution in the TD,as well as in the similar areas around the world.展开更多
On August 24,2020,General Secretary Xi Jinping,for the first time,raised the idea that“the world has entered a period of turbulence and change”at a symposium with experts in the economic and social fields.The report...On August 24,2020,General Secretary Xi Jinping,for the first time,raised the idea that“the world has entered a period of turbulence and change”at a symposium with experts in the economic and social fields.The report to the 20th National Congress of the Communist Party of China(CPC)further elaborated on the notion that“the world has entered a new period of turbulence and change”.展开更多
The Light Detection and Ranging(LiDAR)data analysis method has emerged as a powerful and versatile tool for characterizing atmospheric conditions and modeling light propagation through various media.In the context of ...The Light Detection and Ranging(LiDAR)data analysis method has emerged as a powerful and versatile tool for characterizing atmospheric conditions and modeling light propagation through various media.In the context of renewable energy,particularly wind energy,LiDAR is increasingly utilized to analyze wind flow,turbine wake effects,and turbulence in complex terrains.This study focuses on advancing LiDAR data interpretation through the development and application of the LiDAR Statistical Barnes Objective Analysis(LiSBOA)method.LiSBOA enhances the capacity of scanning LiDAR systems by enabling more precise optimization of scan configurations and improving the retrieval of wind statistics across Cartesian grids.Unlike conventional approaches,LiSBOA offers fine-grained control over azimuthal resolution and spatial filtering,which allows for the detailed reconstruction of wind fields and turbulence structures.These capabilities are crucial for accurately simulating wind turbine wakes and power capture,particularly in environments with variable atmospheric stability and complex topography.Field deployments and comparative assessments against traditional meteorological mast data demonstrate the effectiveness of LiSBOA.The method reduces wind velocity estimation errors to within 3%and increases the accuracy of turbulence intensity measurements by over 4%.Such improvements are significant for enhancing wind resource assessment,optimizing turbine placement,and refining control strategies for operational turbines.LiSBOA represents a robust advancement in LiDAR data processing for wind energy applications.By addressing limitations in spatial resolution and measurement uncertainty,it supports more reliable modeling of wake interactions and flow variability.This work contributes to improving the efficiency and reliability of wind energy systems through advanced remote sensing and statistical analysis techniques.展开更多
Daytime star images captured by dedicated near-space star sensors are characterized by short exposures,high noise,and low Signal-to-Noise Ratios(SNRs).Such imaging is also affected by atmospheric turbulence,causing op...Daytime star images captured by dedicated near-space star sensors are characterized by short exposures,high noise,and low Signal-to-Noise Ratios(SNRs).Such imaging is also affected by atmospheric turbulence,causing optical phenomena,such as scintillation,distortion,and jitter.This causes difficulty in recording high-precision star images during the daytime.This study proposes an adaptive star point extraction method based on dynamically predicting stars'positions.First,it predicts the approximate position of stars based on the star catalog,sensor attitude,observation time,and other information,improving the extraction accuracy.Second,it employs a regional SNR sorting method that adaptively selects star images with higher SNRs,suppressing the scintillation effect and enhancing the SNR of star images.Third,depending on the star's motion trajectory characteristics on the image plane,it utilizes the centroid smoothing method for extraction,thus overcoming the impact of star drift.Field experiments demonstrate that the proposed method can effectively overcome star scintillation,drift,and irregular imaging caused by atmospheric turbulence,achieving a 100%success rate.Moreover,the extraction accuracy improves by more than 80%compared to traditional adaptive methods,attaining a value of 0.05 pixels(0.5"),thereby meeting the requirements of daytime astronomical attitude determination and positioning.展开更多
The turbulent characteristics of the top-blown Laval nozzle and the influence of pressure and Mach number were studied through numerical simulation.With 2.72%error between the results and the empirical formula,the res...The turbulent characteristics of the top-blown Laval nozzle and the influence of pressure and Mach number were studied through numerical simulation.With 2.72%error between the results and the empirical formula,the results are reliable.Nozzle fluid is influenced by pipe structure,causing pressure and density to drop as speed increases.Differences in pressure and velocity between the jet and surrounding gas lead to jet velocity attenuation,flow expansion,deflection,and eddy currents.The optimal top blowing pressure is 0.6 MPa,and the center velocity and width of the jet are 345 m/s and 0.124 m,respectively,at 20De(De is the nozzle exit diameter).It achieves a maximum jet velocity of 456 m/s.The optimal nozzle Mach number is 1.75,with a maximum jet velocity of 451 m/s.At 20D_(e),the jet center velocity is 338 m/s,with a width of 0.12 m.展开更多
Primordial black holes(PBHs) offer a compelling candidate for dark matter. The production of PBHs through well-tested and accepted physical processes is highly worthy of investigation. This work highlights the role of...Primordial black holes(PBHs) offer a compelling candidate for dark matter. The production of PBHs through well-tested and accepted physical processes is highly worthy of investigation. This work highlights the role of turbulences in the very early universe in sustaining intense and persistent fluctuations in energy or mass density,which could provide a natural mechanism for PBH formation in the primordial universe. We analyze the mass range and abundance of PBHs produced in the magnetohydrodynamic turbulence induced by the electroweak phase transition. Remarkably, we find that the mass range of the produced PBHs falls within the most viable“asteroid mass” window from the present-day observations, and within natural parameter regions their abundance can be sufficiently large. These findings suggest that PBHs produced during magnetohydrodynamic turbulence in the very early universe may comprise a dominant part of dark matter.展开更多
A modified three-dimensional turbulence parameterization scheme,implemented by replacing the conventional eddydiffusivity formulation with the H-gradient model,has shown good performance in representing the subgrid-sc...A modified three-dimensional turbulence parameterization scheme,implemented by replacing the conventional eddydiffusivity formulation with the H-gradient model,has shown good performance in representing the subgrid-scale(SGS)turbulent fluxes associated with convective clouds in idealized tropical cyclone(TC)simulations.To evaluate the capability of the modified scheme in simulating real TCs,two sets of simulations of TC Soudelor(2015),one with the modified scheme and the other with the original scheme,are conducted.Comparisons with observations and coarse-grained results from large eddy simulation benchmarks demonstrate that the modified scheme improves the forecasting of the intensity and structure,as well as the SGS turbulent fluxes of Soudelor.Using the modified turbulence scheme,a TC with stronger intensity,smaller size,a shallower but stronger inflow layer,and a more intense but less inclined convective updraft is simulated.The rapid intensification process and secondary eyewall features can also be captured better by the modified scheme.By analyzing the mechanism by which turbulent transport impacts the intensity and structure of TCs,it is shown that accurately representing the turbulent transport associated with convective clouds above the planetary boundary layer helps to initiate the TC spin-up process.展开更多
The Vortex Particle Method(VPM)is a meshless Lagrangian vortex method.Its low numerical dissipation is exceptionally suitable for wake simulation.Nevertheless,the inadequate numerical stability of VPM prevents its wid...The Vortex Particle Method(VPM)is a meshless Lagrangian vortex method.Its low numerical dissipation is exceptionally suitable for wake simulation.Nevertheless,the inadequate numerical stability of VPM prevents its widespread application in high Reynolds number flow and shear turbulence.To better simulate these flows,this paper proposes the stability-enhanced VPM based on a Reformulated VPM(RVPM)constrained by conservation of angular momentum,integrating a relaxation scheme to suppress the divergence of the vorticity field,and further coupling the Sub-Grid Scale(SGS)model to account for the turbulence dissipation caused by vortex advection and vortex stretching.The validity of the RVPM is confirmed by simulating an isolated vortex ring's evolution.The results also demonstrate that the relaxation scheme of vorticity enhances the numerical stability of the VPM by mitigating the divergence of the vorticity field.The leapfrogging vortex rings simulation demonstrates that the RVPM with the present SGS model can more precisely feature the leapfrog and fusion of vortex rings and has improved numerical stability in high Reynolds number flows.The round turbulent jet simulation confirms that the stability-enhanced VPM can stably simulate shear turbulence and accurately resolve fluctuating components and Reynolds stresses in the turbulence.展开更多
The decoherence of high-dimensional orbital angular momentum(OAM)entanglement in the weak scintillation regime has been investigated.In this study,we simulate atmospheric turbulence by utilizing a multiple-phase scree...The decoherence of high-dimensional orbital angular momentum(OAM)entanglement in the weak scintillation regime has been investigated.In this study,we simulate atmospheric turbulence by utilizing a multiple-phase screen imprinted with anisotropic non-Kolmogorov turbulence.The entanglement negativity and fidelity are introduced to quantify the entanglement of a high-dimensional OAM state.The numerical evaluation results indicate that entanglement negativity and fidelity last longer for a high-dimensional OAM state when the azimuthal mode has a lower value.Additionally,the evolution of higher-dimensional OAM entanglement is significantly influenced by OAM beam parameters and turbulence parameters.Compared to isotropic atmospheric turbulence,anisotropic turbulence has a lesser influence on highdimensional OAM entanglement.展开更多
We present the approaches to implementing the k-√k L turbulence model within the framework of the high-order discontinuous Galerkin(DG)method.We use the DG discretization to solve the full Reynolds-averaged Navier-St...We present the approaches to implementing the k-√k L turbulence model within the framework of the high-order discontinuous Galerkin(DG)method.We use the DG discretization to solve the full Reynolds-averaged Navier-Stokes equations.In order to enhance the robustness of approaches,some effective techniques are designed.The HWENO(Hermite weighted essentially non-oscillatory)limiting strategy is adopted for stabilizing the turbulence model variable k.Modifications have been made to the model equation itself by using the auxiliary variable that is always positive.The 2nd-order derivatives of velocities required in computing the von Karman length scale are evaluated in a way to maintain the compactness of DG methods.Numerical results demonstrate that the approaches have achieved the desirable accuracy for both steady and unsteady turbulent simulations.展开更多
In view of the feature of flight flutter test data with atmospheric turbulence excitation, a method which combines wavelet transformation with random decrement technique for identifying flight flutter modal parameters...In view of the feature of flight flutter test data with atmospheric turbulence excitation, a method which combines wavelet transformation with random decrement technique for identifying flight flutter modal parameters is presented. This approach firstly uses random decrement technique to gain free decays corresponding to the acceleration response of the structure to some non-zero initial conditions. Then the continuous Morlet wavelet transformation of the free decays is performed; and the Parseval formula and residue theorem are used to simplify the transformation. The maximal wavelet transformation coefficients in different scales are searched out by means of band-filtering characteristic of Morlet wavelet, and then the modal parameters are identified according to the relationships with maximal modulus and angle of the wavelet transform. In addition, the condition of modal uncoupling is discussed according to variation trend of flight flutter modal parameters in the flight flutter state. The analysis results of simulation and flight flutter test data show that this approach is not only simple, effective and feasible, but also having good noise immunity.展开更多
This article deals with generation and application of three-dimensional (3D) atmospheric turbulence field in large aircraft real-time flight simulation. The modeling requirements for the turbulence field of large airc...This article deals with generation and application of three-dimensional (3D) atmospheric turbulence field in large aircraft real-time flight simulation. The modeling requirements for the turbulence field of large aircraft flight simulation are analyzed here. The spatial turbulence field is generated in the frequency domain by using the Monte Carlo method,and then transformed back to the time domain with the 3D inverse Fourier transform. The von Karman model is adopted for an accurate description of the turb...展开更多
Scaling is an important measure of multi-scale fluctuation systems. Turbulence as the most remarkable multi-scale system possesses scaling over a wide range of scales. She-Leveque （SL） hierarchical symmetry, since i...Scaling is an important measure of multi-scale fluctuation systems. Turbulence as the most remarkable multi-scale system possesses scaling over a wide range of scales. She-Leveque （SL） hierarchical symmetry, since its publication in 1994, has received wide attention. A number of experimental, numerical and theoretical work have been devoted to its verification, extension, and modification. Application to the understanding of magnetohydrodynamic turbulence, motions of cosmic baryon fluids, cosmological supersonic turbulence, natural image, spiral turbulent patterns, DNA anomalous composition, human heart variability are just a few among the most successful examples. A number of modified scaling laws have been derived in the framework of the hierarchical symmetry, and the SL model parameters are found to reveal both the organizational order of the whole system and the properties of the most significant fluctuation structures. A partial set of work related to these studies are reviewed. Particular emphasis is placed on the nature of the hierarchical symmetry. It is suggested that the SL hierarchical symmetry is a new form of the self-organization principle for multi-scale fluctuation systems, and can be employed as a standard analysis tool in the general multi-scale methodology. It is further suggested that the SL hierarchical symmetry implies the existence of a turbulence ensemble. It is speculated that the search for defining the turbulence ensemble might open a new way for deriving statistical closure equations for turbulence and other multi-scale fluctuation systems.展开更多
On the basis of the fact that physical world possesses hierarchical structure and the concepts of nonstandard mathematics, a new description of turbulence was presented. Fundamental equations of turbulent flows were a...On the basis of the fact that physical world possesses hierarchical structure and the concepts of nonstandard mathematics, a new description of turbulence was presented. Fundamental equations of turbulent flows were also given. It is natural in this nonstandard picture of turbulence that the closure methods are obtained and seem to be precise.展开更多
文摘Restoration of phase aberrations is crucial for addressing atmospheric turbulence in light propagation.Traditional restoration algorithms based on Zernike polynomials(ZPs)often encounter challenges related to high computational complexity and insufficient capture of high-frequency phase aberration components,so we proposed a Principal-Component-Analysis-based method for representing phase aberrations.This paper discusses the factors influencing the accuracy of restoration,mainly including the sample space size and the sampling interval of D/r_(0),on the basis of characterizing phase aberrations by Principal Components(PCs).The experimental results show that a larger D/r_(0)sampling interval can ensure the generalization ability and robustness of the principal components in the case of a limited amount of original data,which can help to achieve high-precision deployment of the model in practical applications quickly.In the environment with relatively strong turbulence in the test set of D/r_(0)=24,the use of 34 terms of PCs can improve the corrected Strehl ratio(SR)from 0.007 to 0.1585,while the Strehl ratio of the light spot after restoration using 34 terms of ZPs is only 0.0215,demonstrating almost no correction effect.The results indicate that PCs can serve as a better alternative in representing and restoring the characteristics of atmospheric turbulence induced phase aberrations.These findings pave the way to use PCs of phase aberrations with fewer terms than traditional ZPs to achieve data dimensionality reduction,and offer a reference to accelerate and stabilize the model and deep learning based adaptive optics correction.
基金jointly funded by the National Science Foundation of China(No.42405069)the University Natural Sciences Research Project of Anhui Province(Nos.2023AH052201 and 2023AH052184)+1 种基金the 2023 Talent Research Fund Project of Hefei University(No.23RC01)the Technical Development Project of Hefei University(Nos.902/22050124128,902/22050124148 and 902/22050124250)。
文摘Atmospheric turbulence is an important parameter affecting laser atmospheric transmission.This paper reports on a self-developed atmospheric turbulence detection Li DAR system(scanning differential image motion Li DAR(DIM-Li DAR)system).By designing and simulating the optical system of atmospheric turbulence detection Li DAR,the basic optical imaging accuracy has been determined.
基金supported by the Japanese Ministry of Education,Culture,Sports,Science and Technol-ogy through Grants-in-Aid(Grant Nos.21K03859 and 22H01684)the Kurita Water and Environment Foundation(Grant No.25B042)the Okayama Foundation for Science and Technology(2025).
文摘This study evaluates the accuracy of large-eddy simulation(LES)analyses using a commonly used subgrid-scale(SGS)model based on the eddy viscosity hypothesis.The evaluation is performed by examining the Reynolds number dependence of turbulence maintained by anisotropic and isotropic forcing techniques derived from Tay-lor analytical solutions.The Smagorinsky model,the Vreman model,and the coherent structure model are used as SGS models.LES outcomes were evaluated against those produced by direct numerical simulation(DNS).In contrast to the results with isotropic forcing,the turbulent kinetic energy of anisotropic forcing-induced tur-bulence,as calculated by DNS,exhibits a minimum in the intermediate Reynolds number range.However,all three LES analyses fail to reproduce this minimum and instead show overestimated values.This discrepancy is attributed to reduced spatial inhomogeneity of the turbulent diffusion,pressure diffusion,and pressure-strain correlation terms in the transport equations of the velocity fluctuation intensities in this Reynolds number range.Visualization results for the LES and DNS analyses further show that within this range,LES analyses reproduce two-dimensional tubular flow structures that are not observed in DNS results.
基金Supported by the National Key R&D Program of China(2022YFB3303500).
文摘Numerical simulations were conducted on a 10-blade Sevik rotor ingesting wake downstream of two turbulence-generating grids.These simulations were based on implicit large-eddy simulation(ILES)and the boundary data immersion method(BDIM)for compressible flows,which were solved using a fully self-programmed Fortran code.Results show that the predicted thrust spectrum aligns closely with the experimental measurements.In addition,it captures the thrust dipole directivity of the noise around the rotating propeller due to random pressure pulsations on the blades,as well as the flow structures simultaneously.Furthermore,the differences in the statistical characteristics,flow structures,and low-frequency broadband thrust spectra due to different turbulence levels were investigated.This analysis indicates that the interaction between the upstream,which is characterized by a lower turbulence level and a higher turbulent length of scale,and the rotating propeller results in a lower amplitude in force spectra and a slight increase in the scale of tip vortices.
基金King Saud University for funding this work through Researchers Supporting Project number(RSPD2024R697),King Saud University,Riyadh,Saudi Arabiafinancial support European Union under the REFRESH-Research Excellence For REgion Sustainability and High-tech Industries project number CZ.10.03.01/00/22_/0000048 via the Operational Programme Just Transition.
文摘While Metaheuristic optimization techniques are known to work well for clustering and large-scale numerical optimization,algorithms in this category suffer from issues like reinforcement stagnation and poor late-stage refinement.In this paper,we propose the Improved Geyser-Inspired Optimization Algorithm(IGIOA),an enhancement of the Geyser-Inspired Optimization Algorithm(GIOA),which integrates two primary components:the Adaptive Turbulence Operator(ATO)and the Dynamic Pressure Equilibrium Operator(DPEO).ATO allows IGIOA to periodically disrupt stagnation and explore different regions by using turbulence,while DPEO ensures refinement in later iterations by adaptively modulating convergence pressure.We implemented IGIOA on 23 benchmark functions with both unimodal and multimodal contours,in addition to eight problems pertaining to cluster analysis at the UCI.IGIOA,out of all the tested methods,was able to converge most accurately while also achieving a stable convergence rate.The mitigation of premature convergence and low-level exploitation was made possible by the turbulence and pressure-based refinements.The findings from the tests confirm that the adaptation of baseline strategies by IGIOA helps deal with complex data distributions more effectively.However,additional hyperparameters which add complexity are introduced,along with increased computational cost.These include automatic tuning of parameters,ensemble or parallel variations,and hybridization with dedicated local search strategies to extend the reach of IGIOA for general optimization while also specializing it for clustering focused tasks and applications.
基金financially supported by"Tianshan Talent"Training Program-Science and Technology Innovation Team(Tianshan Innovation Team)Project(2022TSYCTD0007)the Youth Innovation Team of China Meteorological Administration(CMA2024QN13)+2 种基金the Central Government Guidance Funds for Local Science and Technology Development Program(ZYYD2025ZY21)the S&T Development Fund of Chinese Academy of Meteorological Sciences(2021KJ034)the Xinjiang Science Fund for Distinguished Young Scholars(2022D01E07).
文摘Due to the arid and sandy surface of the Taklimakan Desert(TD)in China,the turbulence structure and vertical distribution of ozone exhibit unique and complex characteristics.However,few studies have focused on these issues.To reveal the variation characteristics of summertime atmospheric turbulence and ozone concentration over the TD,we conducted joint detection experiments in July 2016 and July 2021 at Tazhong in the hinterland of the TD using an eddy covariance detection system,a GPS(Global Positioning System)sounding system,and a meteorological gradient tower.Using methods such as statistical analysis,nonlinear fitting,and Fast Fourier Transform,this study analyzed and processed parameters including temperature,relative humidity,wind speed,turbulence parameters,turbulence spectra,and ozone concentration.The high average temperature is accompanied by low relative humidity over the TD,showing a negative correlation between the two.The temperature of the 10.0-cm-deep sand layer lags the near-surface air temperature by nearly 4 h.From 09:30 to 21:00(Beijing Time),under conditions where the sensible heat flux is positive but stability parameter(z/L,where z is the height and L is the Obukhov length)is negative,the atmosphere is heated by the land surface,with the occurrence of unstable stratification;however,the conditions are the opposite(sensible heat flux is negative and z/L is positive)after 22:00,which are accompanied with the cooling of the surface radiation,occurrence of temperature inversion in the lower atmosphere,and stable stratification.A positive correlation is identified between the diurnal variation of turbulent kinetic energy(TKE)and the atmospheric boundary layer(ABL)height,with significant contributions from both the buoyancy and shear terms during the daytime.Under unstable stratification,the normalized standard deviations of the three-dimensional wind speed,temperature,and humidity conform to the Monin-Obukhov Similarity Theory(MOST).As the stability parameter z/L transitions from strongly unstable to strongly stable,the energy of the dimensionless turbulent velocity spectra gradually decreases and conforms to the -2/3 power law within the inertial subrange.In the hinterland of the TD,the summertime tropospheric ozone concentration remains below approximately 0.70×10^(-6)(volume concentration).Above the troposphere,within the range of 16,500.0-30,000.0 m,a significant increasing trend is identified in the ozone concentration with altitude.At an altitude of 30,000.0 m,the maximum ozone concentration can reach up to 7.50×10^(-6).The research findings provide both theoretical and data foundations for future in-depth studies of turbulent motion and ozone concentration distribution in the TD,as well as in the similar areas around the world.
文摘On August 24,2020,General Secretary Xi Jinping,for the first time,raised the idea that“the world has entered a period of turbulence and change”at a symposium with experts in the economic and social fields.The report to the 20th National Congress of the Communist Party of China(CPC)further elaborated on the notion that“the world has entered a new period of turbulence and change”.
文摘The Light Detection and Ranging(LiDAR)data analysis method has emerged as a powerful and versatile tool for characterizing atmospheric conditions and modeling light propagation through various media.In the context of renewable energy,particularly wind energy,LiDAR is increasingly utilized to analyze wind flow,turbine wake effects,and turbulence in complex terrains.This study focuses on advancing LiDAR data interpretation through the development and application of the LiDAR Statistical Barnes Objective Analysis(LiSBOA)method.LiSBOA enhances the capacity of scanning LiDAR systems by enabling more precise optimization of scan configurations and improving the retrieval of wind statistics across Cartesian grids.Unlike conventional approaches,LiSBOA offers fine-grained control over azimuthal resolution and spatial filtering,which allows for the detailed reconstruction of wind fields and turbulence structures.These capabilities are crucial for accurately simulating wind turbine wakes and power capture,particularly in environments with variable atmospheric stability and complex topography.Field deployments and comparative assessments against traditional meteorological mast data demonstrate the effectiveness of LiSBOA.The method reduces wind velocity estimation errors to within 3%and increases the accuracy of turbulence intensity measurements by over 4%.Such improvements are significant for enhancing wind resource assessment,optimizing turbine placement,and refining control strategies for operational turbines.LiSBOA represents a robust advancement in LiDAR data processing for wind energy applications.By addressing limitations in spatial resolution and measurement uncertainty,it supports more reliable modeling of wake interactions and flow variability.This work contributes to improving the efficiency and reliability of wind energy systems through advanced remote sensing and statistical analysis techniques.
基金funded by the National Natural Science Foundation of China(Nos.42374011,42074013)through the Natural Science Foundation’s Outstanding Youth Fund Program of Henan Province,China(Nos.242300421150,242300421151)。
文摘Daytime star images captured by dedicated near-space star sensors are characterized by short exposures,high noise,and low Signal-to-Noise Ratios(SNRs).Such imaging is also affected by atmospheric turbulence,causing optical phenomena,such as scintillation,distortion,and jitter.This causes difficulty in recording high-precision star images during the daytime.This study proposes an adaptive star point extraction method based on dynamically predicting stars'positions.First,it predicts the approximate position of stars based on the star catalog,sensor attitude,observation time,and other information,improving the extraction accuracy.Second,it employs a regional SNR sorting method that adaptively selects star images with higher SNRs,suppressing the scintillation effect and enhancing the SNR of star images.Third,depending on the star's motion trajectory characteristics on the image plane,it utilizes the centroid smoothing method for extraction,thus overcoming the impact of star drift.Field experiments demonstrate that the proposed method can effectively overcome star scintillation,drift,and irregular imaging caused by atmospheric turbulence,achieving a 100%success rate.Moreover,the extraction accuracy improves by more than 80%compared to traditional adaptive methods,attaining a value of 0.05 pixels(0.5"),thereby meeting the requirements of daytime astronomical attitude determination and positioning.
基金supported by the National Key Research and Development Project of China(No.2022YFC3902001)the National Natural Science Foundation of China(No.52004340)the Guangxi Innovation-driven Development Project,China(Nos.Gui 2021AA12006 and 2021AB26024)。
文摘The turbulent characteristics of the top-blown Laval nozzle and the influence of pressure and Mach number were studied through numerical simulation.With 2.72%error between the results and the empirical formula,the results are reliable.Nozzle fluid is influenced by pipe structure,causing pressure and density to drop as speed increases.Differences in pressure and velocity between the jet and surrounding gas lead to jet velocity attenuation,flow expansion,deflection,and eddy currents.The optimal top blowing pressure is 0.6 MPa,and the center velocity and width of the jet are 345 m/s and 0.124 m,respectively,at 20De(De is the nozzle exit diameter).It achieves a maximum jet velocity of 456 m/s.The optimal nozzle Mach number is 1.75,with a maximum jet velocity of 451 m/s.At 20D_(e),the jet center velocity is 338 m/s,with a width of 0.12 m.
基金supported by the International Partnership Program of the Chinese Academy of Sciences (Grant No.025GJHZ2023106GC)。
文摘Primordial black holes(PBHs) offer a compelling candidate for dark matter. The production of PBHs through well-tested and accepted physical processes is highly worthy of investigation. This work highlights the role of turbulences in the very early universe in sustaining intense and persistent fluctuations in energy or mass density,which could provide a natural mechanism for PBH formation in the primordial universe. We analyze the mass range and abundance of PBHs produced in the magnetohydrodynamic turbulence induced by the electroweak phase transition. Remarkably, we find that the mass range of the produced PBHs falls within the most viable“asteroid mass” window from the present-day observations, and within natural parameter regions their abundance can be sufficiently large. These findings suggest that PBHs produced during magnetohydrodynamic turbulence in the very early universe may comprise a dominant part of dark matter.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFC3000803)the National Natural Science Foundation of China(Grant Nos.42375149,41975133 and 42205070)the Shanghai Pujiang Program(Grant No.22PJ1415900)。
文摘A modified three-dimensional turbulence parameterization scheme,implemented by replacing the conventional eddydiffusivity formulation with the H-gradient model,has shown good performance in representing the subgrid-scale(SGS)turbulent fluxes associated with convective clouds in idealized tropical cyclone(TC)simulations.To evaluate the capability of the modified scheme in simulating real TCs,two sets of simulations of TC Soudelor(2015),one with the modified scheme and the other with the original scheme,are conducted.Comparisons with observations and coarse-grained results from large eddy simulation benchmarks demonstrate that the modified scheme improves the forecasting of the intensity and structure,as well as the SGS turbulent fluxes of Soudelor.Using the modified turbulence scheme,a TC with stronger intensity,smaller size,a shallower but stronger inflow layer,and a more intense but less inclined convective updraft is simulated.The rapid intensification process and secondary eyewall features can also be captured better by the modified scheme.By analyzing the mechanism by which turbulent transport impacts the intensity and structure of TCs,it is shown that accurately representing the turbulent transport associated with convective clouds above the planetary boundary layer helps to initiate the TC spin-up process.
基金co-supported by the National Natural Science Foundation of China(No.12402272)the Natural Science Basic Research Program of Shaanxi Province,China(No.2024JC-YBQN-0024)the Fundamental Research Funds for the Central Universities,China(No.D5000240030)。
文摘The Vortex Particle Method(VPM)is a meshless Lagrangian vortex method.Its low numerical dissipation is exceptionally suitable for wake simulation.Nevertheless,the inadequate numerical stability of VPM prevents its widespread application in high Reynolds number flow and shear turbulence.To better simulate these flows,this paper proposes the stability-enhanced VPM based on a Reformulated VPM(RVPM)constrained by conservation of angular momentum,integrating a relaxation scheme to suppress the divergence of the vorticity field,and further coupling the Sub-Grid Scale(SGS)model to account for the turbulence dissipation caused by vortex advection and vortex stretching.The validity of the RVPM is confirmed by simulating an isolated vortex ring's evolution.The results also demonstrate that the relaxation scheme of vorticity enhances the numerical stability of the VPM by mitigating the divergence of the vorticity field.The leapfrogging vortex rings simulation demonstrates that the RVPM with the present SGS model can more precisely feature the leapfrog and fusion of vortex rings and has improved numerical stability in high Reynolds number flows.The round turbulent jet simulation confirms that the stability-enhanced VPM can stably simulate shear turbulence and accurately resolve fluctuating components and Reynolds stresses in the turbulence.
基金supported by the Project of the Hubei Provincial Department of Science and Technology(Grant Nos.2022CFB957,2022CFB475)the National Natural Science Foundation of China(Grant No.11847118)。
文摘The decoherence of high-dimensional orbital angular momentum(OAM)entanglement in the weak scintillation regime has been investigated.In this study,we simulate atmospheric turbulence by utilizing a multiple-phase screen imprinted with anisotropic non-Kolmogorov turbulence.The entanglement negativity and fidelity are introduced to quantify the entanglement of a high-dimensional OAM state.The numerical evaluation results indicate that entanglement negativity and fidelity last longer for a high-dimensional OAM state when the azimuthal mode has a lower value.Additionally,the evolution of higher-dimensional OAM entanglement is significantly influenced by OAM beam parameters and turbulence parameters.Compared to isotropic atmospheric turbulence,anisotropic turbulence has a lesser influence on highdimensional OAM entanglement.
基金supported by the National Natural Science Foundation of China(Grant Nos.92252201 and 11721202)the Fundamental Research Funds for the Central Universities.
文摘We present the approaches to implementing the k-√k L turbulence model within the framework of the high-order discontinuous Galerkin(DG)method.We use the DG discretization to solve the full Reynolds-averaged Navier-Stokes equations.In order to enhance the robustness of approaches,some effective techniques are designed.The HWENO(Hermite weighted essentially non-oscillatory)limiting strategy is adopted for stabilizing the turbulence model variable k.Modifications have been made to the model equation itself by using the auxiliary variable that is always positive.The 2nd-order derivatives of velocities required in computing the von Karman length scale are evaluated in a way to maintain the compactness of DG methods.Numerical results demonstrate that the approaches have achieved the desirable accuracy for both steady and unsteady turbulent simulations.
基金National Natural Science Foundation of China(60134010)
文摘In view of the feature of flight flutter test data with atmospheric turbulence excitation, a method which combines wavelet transformation with random decrement technique for identifying flight flutter modal parameters is presented. This approach firstly uses random decrement technique to gain free decays corresponding to the acceleration response of the structure to some non-zero initial conditions. Then the continuous Morlet wavelet transformation of the free decays is performed; and the Parseval formula and residue theorem are used to simplify the transformation. The maximal wavelet transformation coefficients in different scales are searched out by means of band-filtering characteristic of Morlet wavelet, and then the modal parameters are identified according to the relationships with maximal modulus and angle of the wavelet transform. In addition, the condition of modal uncoupling is discussed according to variation trend of flight flutter modal parameters in the flight flutter state. The analysis results of simulation and flight flutter test data show that this approach is not only simple, effective and feasible, but also having good noise immunity.
文摘This article deals with generation and application of three-dimensional (3D) atmospheric turbulence field in large aircraft real-time flight simulation. The modeling requirements for the turbulence field of large aircraft flight simulation are analyzed here. The spatial turbulence field is generated in the frequency domain by using the Monte Carlo method,and then transformed back to the time domain with the 3D inverse Fourier transform. The von Karman model is adopted for an accurate description of the turb...
基金the National Natural Science Foundation(90716008)MOST 973 project (2009CB724100)
文摘Scaling is an important measure of multi-scale fluctuation systems. Turbulence as the most remarkable multi-scale system possesses scaling over a wide range of scales. She-Leveque （SL） hierarchical symmetry, since its publication in 1994, has received wide attention. A number of experimental, numerical and theoretical work have been devoted to its verification, extension, and modification. Application to the understanding of magnetohydrodynamic turbulence, motions of cosmic baryon fluids, cosmological supersonic turbulence, natural image, spiral turbulent patterns, DNA anomalous composition, human heart variability are just a few among the most successful examples. A number of modified scaling laws have been derived in the framework of the hierarchical symmetry, and the SL model parameters are found to reveal both the organizational order of the whole system and the properties of the most significant fluctuation structures. A partial set of work related to these studies are reviewed. Particular emphasis is placed on the nature of the hierarchical symmetry. It is suggested that the SL hierarchical symmetry is a new form of the self-organization principle for multi-scale fluctuation systems, and can be employed as a standard analysis tool in the general multi-scale methodology. It is further suggested that the SL hierarchical symmetry implies the existence of a turbulence ensemble. It is speculated that the search for defining the turbulence ensemble might open a new way for deriving statistical closure equations for turbulence and other multi-scale fluctuation systems.
文摘On the basis of the fact that physical world possesses hierarchical structure and the concepts of nonstandard mathematics, a new description of turbulence was presented. Fundamental equations of turbulent flows were also given. It is natural in this nonstandard picture of turbulence that the closure methods are obtained and seem to be precise.
