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The Effects of Turbulence Intensity and Tip Speed Ratio on the coherent structure of Horizontal-Axis Wind Turbine Wake:A Wind Tunnel Experiment

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Energy Engineering 2022年第6期119卷 2297-2317页

作者： Yuxia Han Jianwen Wang Xin Li Xueqing Dong Caifeng Wen School of Energy and Power Engineering Inner Mongolia University of TechnologyHohhot010051China Key Laboratory of Wind Energy and Solar Energy Utilization Technology Ministry of EducationInner Mongolia University of TechnologyHohhot010051China Power Research Institute Inner Mongolia Electric Power Group Co.Ltd.Hohhot010020China

The evolution laws of the large-eddy coherent structure of the wind turbine wake have been evaluated via wind tunnel experiments under uniform and turbulent inflow conditions.The spatial correlation coefficients,the turbulence integral scales and power spectrum are obtained at different tip speed ratios(TSRs)based on the time-resolved particle image velocity(TR-PIV)technique.The results indicate that the large-eddy coherent structures are more likely to dissipate with an increase in turbulence intensity and TSR.Furthermore,the spatial correlation of the longitudinal pulsation velocity is greater than its axial counterpart,resulting into a wake turbulence dominated by the longitudinal pulsation.With an increase of turbulence intensity,the integral scale of the axial turbulence increases,meanwhile,its longitudinal counterpart decreases.Owing to an increase in TSR,the integral scale of axial turbulence decreases,whereas,that of the longitudinal turbulence increases.By analyzing the wake power spectrum,it is found that the turbulent pulsation kinetic energy of the wake structure is mainly concentrated in the low-frequency vortex region.The dissipation rate of turbulent kinetic energy increases with an increase of turbulence intensity and the turbulence is transported and dissipated on a smaller scale vortex,thus promoting the recovery of wake.

关键词： Horizontal axis wind turbine coherent structure turbulence integral scale TR-PIV spatial correlation

RELATION BETWEEN coherent structure AND SCALING LAW IN RAYLEIGH-BENARD CONVECTION BASED ON WAVELET TRANSFORMATION

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Journal of Hydrodynamics 2004年第4期16卷 436-441页

作者： FUQiang JIANGMin XIAKe-qing SchoolofScience P.L.A.UniversityofScienceandTechnologyNanjing211101China Departmentofphysics TheChineseUniversityofHongKongHongKongChina SchoolofScience P.L.A.UniversityofScienceandTechnologyNanjing211101China Departmentofphysics TheChineseUniversityofHongKongHongKongChina

In this paper, the Extended Self Similarity (ESS) was used to study thescaling exponent ξ(q) of temperature data in the Reyleigh-Benard convection and its variation withexperimental measuring locations. The results show that ξ(q) varies with locations and agrees wellwith experimental data. And then the wavelet transformation is used to extract the coherentstructure, by means of the definition of a called non-coherent signal. we can understand theinfluence of coherent structure on ξ(q) and the relations between large scale vortex motions andsmall ones.

关键词： scaling law coherent structure wavelet transformation rayleigh-benardconvection

A KIND OF FAST CHANGING coherent structure IN A TURBULENT BOUNDARY LAYER

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Acta Mechanica Sinica 1999年第3期15卷 193-200页

作者：连淇祥 Institute of Fluid Mechanics Beijing Univ.of Aero.& AstroBeijing 100083China

coherent structures of a turbulent boundary layer were investigated by hydrogen bubble method. A kind of fast changing structure was observed. That is a spot in which all the hydrogen bubbles vanish much faster than in other regions. This investigation verified that dark-spot is formed by a strong sweep from outer layer. Inside a dark-spot the local instantaneous flow speed might be four times of its neighboring high-speed streaks. Comparing with the low/high speed streaks, both dark-spot and the vortical structures around it are changing very fast. Around dark-spot intensive shear layers are formed and indications of the generation of small-scale structures could be observed.

关键词： turbulent boundary layer coherent structure small-scale structure

Scale properties of turbulent transport and coherent structure in stably stratified flows

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Applied Mathematics and Mechanics(English Edition) 2016年第4期37卷 443-458页

作者： Long ZHU Xiang QIU Jianping LUO Yulu LIU School of Mechanical Engineering Shanghai Institute of Technology School of Science Shanghai Institute of Technology Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

The empirical mode decomposition （EMD） is used to study the scale properties of turbulent transport and coherent structures based on velocity and temperature time series in stably stratified turbulence. The analysis is focused on the scale properties of intermittency and coherent structures in different modes and the contributions of energy-contained coherent structures to turbulent scalar counter-gradient transport （CGT）. It is inferred that the velocity intermittency is scattered to more modes with the development of the stratified flow, and the intermittency is enhanced by the vertical stratification, especially in small scales. The anisotropy of the field is presented due to different time scales of coherent structures of streamwise and vertical velocities. There is global counter-gradient heat transport close to the turbulence-generated grid, and there is local counter-gradient heat transport at certain modes in different positions. coherent structures play a principal role in the turbulent vertical transport of temperature.

关键词： stratified turbulence coherent structure counter-gradient transport （CGT）,empirical mode decomposition （EMD）

NUMERICAL RESEARCH ON THE coherent structure IN THE VISCOELASTIC SECOND-ORDER MIXING LAYERS

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Applied Mathematics and Mechanics(English Edition) 1998年第8期19卷 717-723页

作者：余钊圣林建忠 Department of Mechanics State Key Laboratory of Fluid Power Transmission and Control Zhejiang University Hangzhou P. R. China

Numerical simulations have been performed in time-developing plane mixing layers of the viscoelastic second-order fluids with pseudo-spectral method. Roll-up, pairing and merging of large eddies were examined at high Reynolds numbers and low Deborah numbers. The effect of viscoelastics on the evolution of the large coherent structure was shown by making a comparison between the second-order and Newtonian fluids at the same Reynolds numbers.

关键词： mixing layer viscoelastic second-order fluids numerical simulation pseudo-spectral method coherent structure

ON THE MECHANISM OF TURBULENT coherent structure (III)──A STATISTICAL AND DYNAMICALMODEL OF coherent structure AND ITSHEAT TRANSFER MECHANISM

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Applied Mathematics and Mechanics(English Edition) 1998年第8期19卷 705-711页

作者：卢志明刘宇陆 Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai P. R. China

Following Tsai & Ma[1] and Tsai & Liu[2], a statistical and dynamical near-wall turbulent coherent structural model with separate consideration of two different portions:locally generated and upstream-transported large eddies has been established.With this model, heat transfer in a fully developed open channel in the absence of pressure gradient is numerically simulated. Database of fluctuations of velocity and temperature has also been set. Numerical analysis shows the existence of high-low temperature streak caused by near-wall coherent structure and its swing in the lateral direction.Numerical results are in accordance with the computations and experimental results of other researchers.

关键词： coherent structure statistical and dynamical model heat transfer

Gustiness and coherent structure of Strong Winds and Their Role in Dust Emission and Entrainment

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Advances in Atmospheric Sciences 2010年第1期27卷 1-13页

作者：曾庆存程雪玲胡非彭珍 Institute of Atmospheric Physics Chinese Academy of Sciences Department of Atmospheric Science Nanjing University

After the passage of a cold front, spring in northern China, the outbreak of strong wind is often accompanied by dust emissions. Through analyses of data in the atmospheric boundary layer during a typical case, it is revealed there are rather regular gust wave packets superimposed on the basic strong wind flow. The gust-wind wave packets have a period equal to around 3 6 rains and possess coherent structure. As the vertical transport of momentum is decomposed into separate parts by （a） basic flow, （b） gust-wind, and （c） turbulence, they are all in a downwards direction at the lower levels of the atmospheric boundary layer during strong wind periods. However, （a） is the largest, while （b） and （c） are comparable. All these are very different from the case of normal weather. Besides, the friction velocity at the ground surface is also much larger than that of normal weather and should be corrected by taking the contributions of the basic flow and gust-wind into account.The strong basic flow with descending motion is very favorable for soil erosion and sand/dust emissions, but suppresses the entrainment of dust particles by keeping them within the bottom levels of the atmospheric boundary layer. Owing to the coherent structure of gust-wind, dust particles can effectively overcome the systematic descending air motion and penetrate into the middle and upper levels of the atmospheric boundary layer, and then propagate further and diffuse into the troposphere where ascending air motion prevails.

关键词： gust-wind coherent structure descending motion dust storm soil erosion dust entrainment

DYNAMICAL CHARACTERISTICS OF coherent structure IN THE OUTER REGION OF TURBULENCE BOUNDARY LAYER

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Acta Mechanica Sinica 1996年第4期12卷 289-295页

作者：梁在潮 Wuhan University of Hydraulic and Electric Engineering Wuhan 430072China

In the present paper the coherent structures in the outer region of turbulent boundary layer were investigated experimentally and analytically. From the observation of the how field over smooth wall, rough wall and sand wave wall, it was found that the direct effect of wall on the flow structure can reach y(+1) approximate to 100, and both lateral and vertical vortices exist in the outer region, but the coherent structures in the outer region are mainly the formation, development and decay of the large-scale lateral vortices. By experimental and dynamical analysis, some influence factors and their relations associated with the dynamical process of lateral vortices were deduced.

关键词： outer region of turbulence boundary layer coherent structure lateral vortices

Detecting Near-Surface coherent structure Characteristics Using Wavelet Transform with Different Meteorological Elements

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Journal of Tropical Meteorology 2020年第4期26卷 453-460页

作者：方任之王也蓝长星张智杰郑丹蓝光东王宝民 School of Atmospheric Sciences Sun Yat-sen UniversityGuangzhou 510275 China Guangdong Provincial Key Laboratory for Climate Change and Natural Disaster Studies Guangzhou 510275 China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) ZhuhaiGuangdong 519082 China Laboratory for Atmospheric Research Department of Civil and Environmental EngineeringWashington State UniversityPullmanWA 642910 USA Guangdong Provincial Field Observation and Research Station for Climate Environment and Air Quality Change in the Pearl River Estuary Guangzhou 510275 China

In the present study, three wavelet basis functions, i.e., Mexican-hat, Morlet, and Wave, were used to analyze the atmospheric turbulence data obtained from an eddy covariance system in order to determine the effect of six meteorological elements including three-dimensional wind speed, temperature, and CO2and H2O concentrations on the time scale of coherent structures. First, we used the degree of correlation between original and reconstructed waveforms to test the three wavelets’performance when determining the time scale of coherent structures. The Wave wavelet’s reconstructed coherent structure signal best matched the original signal;thus, it was used to further analyze the time scale, number, and time cover of the meteorological elements. We found similar results for all elements, though there was some internal variation, suggesting that coherent structures are not inherently dependent on these elements. Our results provide a basis for proper coherent structure detection in atmospheric turbulence and improve the understanding of similarities and differences between coherent structure characteristics of different meteorological elements, which is helpful for further research into atmospheric turbulence and boundary layers.

关键词： coherent structure atmospheric turbulence atmospheric boundary layer wavelet transform