检索结果-内蒙古大学图书馆

Constrained large-eddy simulation and detached eddy simulation of flow past a commercial aircraft at 14 degrees angle of attack

引用

Science China(physics,Mechanics & Astronomy) 2013年第2期56卷 270-276页

作者： CHEN ShiYi CHEN YingChun XIA ZhenHua QU Kun SHI YiPeng XIAO ZuoLi LIU QiuHong CAI QingDong LIU Feng LEE Cunbiao ZHANG RiKui CAI JinSheng State Key Laboratory for Turbulence and Complex Systems and Center for Applied Physics and Technology College of EngineeringPeking University Shanghai Aircraft Design And Research Institute Commercial Aircraft Corporation of China Ltd. School of Aeronautics Northwestern Polytechnical University

With the development of computational power and numerical algorithms,computational fluid dynamics(CFD) has become an important strategy for the design of aircraft,which significantly reduces the reliance on wind-tunnel and flight *** this paper,we conducted a numerical investigation on the flow past a full commercial aircraft at Mach number 0.2 and 14 degrees angle of attack by means of Reynolds-averaged Navier-Stokes(RANS),detached-eddy simulation(DES) and our newly developed constrained large-eddy simulation(CLES).The objective of this paper is to study the capability of these models in simulating turbulent *** our knowledge,this is the first large-eddy simulation method for full commercial aircraft *** results show that the CLES can predict the mean statistical quantities well,qualitatively consistent with traditional methods,and can capture more small-scale structures near the surface of the aircraft with massive *** study demonstrates that CLES is a promising alternative for simulating real engineering turbulent flows.

关键词： turbulence simulation Reynolds-averaged Navier-Stokes （RANS） detached-eddy simulation （DES） constrained large-eddysimulation （CLES） full-aircraft simulation

来源：评论

学校读者我要写书评

暂无评论

Acceleration of Passive Tracers in Compressible Turbulent Flow

引用

Physical Review Letters 2013年第6期110卷 064503-064503页

作者： Yantao Yang Jianchun Wang Yipeng Shi Zuoli Xiao X. T. He Shiyi Chen State Key Laboratory for Turbulence and Complex Systems Center for Applied Physics and Technology College of Engineering Peking University Beijing 100871 China

In compressible turbulence at high Reynolds and Mach numbers, shocklets emerge as a new type of flow structure in addition to intense vortices as in incompressible turbulence. Using numerical simulation of compressible homogeneous isotropic turbulence, we conduct a Lagrangian study to explore the effects of shocklets on the dynamics of passive tracers. We show that shocklets cause very strong intermittency and short correlation time of tracer acceleration. The probability density function of acceleration magnitude exhibits a −2.5 power-law scaling in the high compression region. Through a heuristic model, we demonstrate that this scaling is directly related to the statistical behavior of strong negative velocity divergence, i.e., the local compression. Tracers experience intense acceleration near shocklets, and most of them are decelerated, usually with large curvatures in their trajectories.

关键词： TRACERS (Chemistry) COMPRESSIBLE flow (Fluid dynamics) REYNOLDS number MACH number turbulence

来源：评论

学校读者我要写书评

暂无评论

Cascade of Kinetic Energy in Three-Dimensional Compressible turbulence

引用

Physical Review Letters 2013年第21期110卷 214505-214505页

作者： Jianchun Wang Yantao Yang Yipeng Shi Zuoli Xiao X. T. He Shiyi Chen State Key Laboratory for Turbulence and Complex Systems Center for Applied Physics and Technology College of Engineering Peking University Beijing 100871 China

The conservative cascade of kinetic energy is established using both Fourier analysis and a new exact physical-space flux relation in a simulated compressible turbulence. The subgrid scale (SGS) kinetic energy flux of the compressive mode is found to be significantly larger than that of the solenoidal mode in the inertial range, which is the main physical origin for the occurrence of Kolmogorov’s −5/3 scaling of the energy spectrum in compressible turbulence. The perfect antiparallel alignment between the large-scale strain and the SGS stress leads to highly efficient kinetic energy transfer in shock regions, which is a distinctive feature of shock structures in comparison with vortex structures. The rescaled probability distribution functions of SGS kinetic energy flux collapse in the inertial range, indicating a statistical self-similarity of kinetic energy cascades.

关键词： KINETIC energy RELATIVISTIC energy FOURIER analysis SOLENOIDS INERTIA (Mechanics) physics research

来源：评论

学校读者我要写书评

暂无评论

A pencil-like magnetoelectric sensor exhibiting ultrahigh coupling properties

A pencil-like magnetoelectric sensor exhibiting ultrahigh co...

引用

作者： Lin, Lizhi Li, Yingwei Soh, Ai-Kah Li, Faxin State Key Laboratory for Turbulence and Complex Systems College of Engineering Peking University Beijing 100871 China HEDPS Center for Applied Physics and Technology Peking University Beijing China School of Engineering Monash University Sunway Campus Malaysia Department of Mechanical Engineering University of Hong Kong Hong Kong Hong Kong

A one-dimensional pencil-like magnetoelectric (ME) sensor prototype is proposed which consists of a magnetostrictive cylinder, a truncated conical spacer, and a piezoelectric disk assembled in a rigid frame. By adopting the displacement-transfer mode in this sensor, not only the strain loss at the ME interface is avoided but also the volume fractions of both phases can be adjusted in a broader range. Using a nonlinear magnetostrictive model and linear piezoelectric model, the ME coupling performance of this sensor is systematically analyzed using lead titanate zirconate (PZT) disks and Terfenol-D cylinder as the components. Results show that such a sensor can practically exhibit giant quasi-static ME field coefficients (α E) and charge density coefficients (α D) as high as 455 V / cm Oe and 480 × 10 - 6 C / m 2 Oe, which is about 10 times and 100 times higher than the best reported values, respectively. Furthermore, the ME coupling properties will decrease considerably when the stiffness of the frame is reduced. The proposed pencil-like ME sensor in this work could be very helpful in the design of ultrasensitive magnetic-field sensors and other ME coupling devices. © 2013 American Institute of physics.

关键词： Lead zirconate titanate

来源：评论

学校读者我要写书评

暂无评论

Refined subgrid-scale model for large-eddy simulation of helical turbulence

引用

Physical Review E 2013年第1期87卷 013006-013006页

作者： Changping Yu Zuoli Xiao State Key Laboratory of Turbulence and Complex Systems College of Engineering Peking University Beijing 100871 P. R. China Center for Applied Physics and Technology College of Engineering Peking University Beijing 100871 P. R. China

A refined two-term helical subgrid-scale (SGS) stress model with respect to that suggested by Li et al. [Phys. Rev. E 74, 026310 (2006)] is designed for large-eddy simulation (LES) of helical turbulence. The model coefficients in the new model are verified a priori to be scale invariant in inertial range, which proves that our model is local in scale. A dynamic method based on minimizing the residual resolved energy and helicity dissipations is suggested to simultaneously evaluate the coefficients of the mixed SGS model as the simulation progresses. In addition, an SGS helicity dissipation (or helicity flux) constraint condition is proposed to optimize the mixed two-term model. Both techniques are first tested and validated in the LES of forced isotropic helical turbulence. The statistical results are analyzed and compared with those obtained from the dynamic Smagorinsky model, the traditional dynamic mixed model, and the direct numerical simulation. It is found that the introduction of this dynamic procedure can help overcome the drawback of the traditional dynamic method which can not capture the negative helicity fluxes and SGS dissipations. The probability density functions of the energy flux and the conditioned helicity flux and SGS stress demonstrate that the helicity flux constrained dynamic SGS model can effectively predict the real SGS helical effects on the resolved scales, such as backscatters of energy and helicity, accurate helicity dissipation rate, and so on. The present models are also applied to the simulation of freely decaying isotropic turbulence with no apparent improvement observed in comparison with the traditional SGS models. The underlying reasons for these issues are addressed in detail.

关键词： turbulence -- Mathematical models STRAINS & stresses (Mechanics) systems design COMPUTER simulation DYNAMICAL systems CONSTRAINTS (physics)

来源：评论

学校读者我要写书评

暂无评论

Correlation between structural relaxation and connectivity of icosahedral clusters in CuZr metallic glass-forming liquids

引用

Physical Review B 2013年第5期88卷 054202-054202页

作者： Z. W. Wu M. Z. Li W. H. Wang K. X. Liu State Key Laboratory of Turbulence and Complex System and Center for Applied Physics and Technology College of Engineering Peking University Beijing 100871 China Department of Physics Renmin University of China Beijing 100872 China Institute of Physics Chinese Academy of Sciences Beijing 100190 China

The correlation between structural relaxation and the medium-range structures formed by icosahedral cluster packing in CuZr supercooled metallic glass-forming liquids was studied via molecular dynamics simulations. We find that compared to the amount of icosahedral clusters, the medium-range structures formed by icosahedral cluster packing play more important and controlling roles in the structural relaxation process of the supercooled liquids. The relaxation times of local structures depend exponentially on the connectivity of local structures. Despite the argument whether there is a specific connection between the static structure and dynamic property of glass formers in particle level, it does exist on larger length scale. Our results demonstrate that dynamical heterogeneity is indeed correlated with the medium-range static atomic structures in the supercooled glass-forming liquids.

关键词： COPPER-zirconium alloys METALLIC glasses AMORPHOUS alloys MOLECULAR dynamics HETEROGENEITY

来源：评论

学校读者我要写书评

暂无评论

Statistics of active and passive scalars in one-dimensional compressible turbulence

引用

Physical Review E 2012年第6期86卷 066307-066307页

作者： Qionglin Ni Shiyi Chen State Key Laboratory of Turbulence and Complex Systems Center for Applied Physics and Technology and Key Laboratory of High Energy Density Physics Simulation Ministry of Education College of Engineering Peking University 100871 Beijing People's Republic of China

Statistics of the active temperature and passive concentration advected by the one-dimensional stationary compressible turbulence at Reλ=2.56×106 and Mt=1.0 is investigated by using direct numerical simulation with all-scale forcing. It is observed that the signal of velocity, as well as the two scalars, is full of small-scale sawtooth structures. The temperature spectrum corresponds to G(k)∝k−5/3, whereas the concentration spectrum acts as a double power law of H(k)∝k−5/3 and H(k)∝k−7/3. The probability distribution functions (PDFs) for the two scalar increments show that both δT and δC are strongly intermittent at small separation distance r and gradually approach the Gaussian distribution as r increases. Simultaneously, the exponent values of the PDF tails for the large negative scalar gradients are qθ=−4.0 and qζ=−3.0, respectively. A single power-law region of finite width is identified in the structure function (SF) of δT; however, in the SF of δC, there are two regions with the exponents taken as a local minimum and a local maximum. As for the scalings of the two SFs, they are close to the Burgers and Obukhov-Corrsin scalings, respectively. Moreover, the negative filtered flux at large scales and the time-increasing total variance give evidences to the existence of an inverse cascade of the passive concentration, which is induced by the implosive collapse in the Lagrangian trajectories.

关键词： turbulence TEMPERATURE COMPUTER simulation GAUSSIAN distribution LAGRANGIAN functions TRAJECTORIES (Mechanics) POWER law (Mathematics)

来源：评论

学校读者我要写书评

暂无评论

Deflection Reduction of GaN Wafer Bowing by Coating or Cutting Grooves in the Substrates

引用

Chinese physics Letters 2011年第4期28卷 190-193页

作者： SUN Tao WANG Ming-Qing SUN Yong-Jian WANG Bo-Ping ZHANG Guo-Yi TONG Yu-Zhen DUAN Hui-Ling State Key Laboratory for Turbulence and Complex Systems Center for Applied Physics and Technology(CAPT)and Department of Mechanics and Aerospace EngineeringCollege of EngineeringPeking UniversityBeijing 100871 State Key Laboratory of Artificial Microstructure and Mesoscopic Physics School of PhysicsPeking UniversityBeijing 100871 Department of Flight Theory Aviation University of Air ForceChangchun 130022

GaN films on sapphire substrates are obtained using the metal-organic chemical vapor deposition growth *** present two methods to reduce the GaN wafer bowing caused by the mismatch of the thermal expansion coefficients(TECs)between the film and the *** first method is to use coating materials on the back side of the substrate whose TECs are smaller than that of the GaN *** second is to cut grooves on the back side of the sapphire substrate and filling the grooves with appropriate materials(e.g.,tungsten,silicon nitride).For each method,we minimize wafer bowing and even reduce it to ***,the two methods can reduce stress concentration and suppress the propagation of cracks in the GaN/sapphire structure.

关键词： sapphire technique coating

来源：评论

学校读者我要写书评

暂无评论

Simulations of gradual domain-switching in polycrystalline ferroelectrics using an optimization-based, multidomain-grain model

Simulations of gradual domain-switching in polycrystalline f...

引用

作者： Li, F.X. Zhou, X.L. State Key Lab for Turbulence and Complex Systems College of Engineering Peking University Beijing 100871 China Center for Applied Physics and Technology Peking University China

An optimization-based computational model is proposed to study the constrained domain switching in polycrystalline ferroelectrics composed of numerous grains, each of which consists of multiple domains. Domain switching is realized by an optimization algorithm to minimize the free energy of each grain and is thus a gradual process with applied loading. Similar to phase field modeling, no priori domain-switching criterion is imposed in the proposed model and its computational efficiency is much higher. The domain textures evolution process can also be captured. Simulation results on both tetragonal and rhombohedral PZT ceramics illustrate the efficiency of this model. © 2010 Elsevier Ltd. All rights reserved.

关键词： Computational efficiency

来源：评论

学校读者我要写书评

暂无评论

Three-dimensional synthetic turbulence constructed by spatially randomized fractal interpolation

引用

Physical Review E 2011年第2期84卷 026328-026328页

作者： Zhi-Xiong Zhang Ke-Qi Ding Yi-Peng Shi Zhen-Su She State Key Laboratory of Turbulence and Complex Systems and College of Engineering Peking University Beijing 100871 P.R. China Center for Applied Physics and Technology Peking University Beijing 100871 P.R. China

A spatially randomized fractal interpolation algorithm to construct three-dimensional synthetic turbulence from original coarse field is reported. As in the one-dimensional case by Ding et al.(Phys. Rev. E 82, 036311, 2010), during the fractal interpolation, positions mapping between large and small scale cubes are chosen randomly, and the stretching factors are drawn from a log-Poisson random multiplicative process. A linear combination function defined as the base part in fractal interpolation and a theoretical energy spectrum model for fully developed turbulence are introduced into the procedure. Statistical analysis shows that the synthetic field displays some properties very close to the direct numeric simulated field, such as probability distributions of velocity, velocity gradient, velocity increment, and the anomalous scaling behavior of the longitude velocity structure functions, which follows the SL94 model precisely. After a short time using direct numeric simulation with the synthetic field as initial data, the typical local dynamical structures described by the teardrop shape of the Q-R plane for empirical turbulence can be reproduced.

关键词： INTERPOLATION algorithms turbulence APPROXIMATION theory SPEED LARGE eddy simulation models

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：