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Spatial artificial neural network model for subgrid-scale stress and heat flux of compressible turbulence

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Theoretical & Applied mechanics Letters 2020年第1期10卷 27-32页

作者： Chenyue Xie Jianchun Wang Hui Li Minping Wan Shiyi Chen Shenzhen Key Laboratory of complex aerospace flows Center for Complex Flows and Soft Matter ResearchDepartment of Mechanics and Aerospace EngineeringSouthern University of Science and TechnologyShenzhen 518055China School of Power and Mechanical engineering Wuhan UniversityWuhan 430072China State Key Laboratory of Turbulence and complex Systems Peking UniversityBeijing 100871China

The subgrid-scale(SGS)stress and SGS heat flux are modeled by using an artificial neural network(ANN)for large eddy simulation(LES)of compressible turbulence.The input features of ANN model are based on the first-order and second-order derivatives of filtered velocity and temperature at different spatial locations.The proposed spatial artificial neural network(SANN)model gives much larger correlation coefficients and much smaller relative errors than the gradient model in an a priori analysis.In an a posteriori analysis,the SANN model performs better than the dynamic mixed model(DMM)in the prediction of spectra and statistical properties of velocity and temperature,and the instantaneous flow structures.

关键词： Compressible turbulence Large eddy simulation Artificial neural network

Multifunctional droplet‐surface interaction effected by bulk properties

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液滴(英文)

液滴(英文) 2023年第1期2卷 4-15页

作者： Xin Tang Centre for complex flows and soft matter research Southern University of Science and TechnologyShenzhenChina department of mechanics and aerospace engineering Southern University of Science and TechnologyShenzhenChina

Droplet‐surface systems are an area of great scientific and technological interest as they widely present in diverse domestic and industrial applications.To modulate the biphasic interaction,intensive efforts have been lavished on interfacial engineering wherein chemical functionalization,physical texturing,and mediating third‐phase introduction are the norm.The surface methods alone are not panacea for many pressing challenges,particularly regarding extreme temperature adaptation,leading some to explore bulk alternatives.Given full play to bulk properties,including optical,electric,mechanical,and thermal types,rich and disparate biphasic systems with superior performances are shown.It is important to understand the nature and similarity of bulk methods in all distinct contexts to identify their strengths and limitations.An existing need remains to summarise and classify the key quantity,design,and mechanism of those budding methods,which may assist the future discovery of solutions to diverse unanswered challenges.

关键词： interaction surface effect

Deconvolutional artificial-neural-network framework for subfilter-scale models of compressible turbulence

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Acta Mechanica Sinica 2021年第12期37卷 1773-1785页

作者： Zelong Yuan Yunpeng Wang Chenyue Xie Jianchun Wang Guangdong Provincial Key Laboratory of Foundemental Turbulence research and Applications Center for Complex Flows and Soft Matter ResearchDepartment of Mechanics and Aerospace EngineeringSouthern University of Science and TechnologyShenzhen 518055China Guangdong-Hong Kong-Macao Joint Laboratory for Data-Driven Fluid mechanics and engineering Applications Southern University of Science and TechnologyShenzhen 518055China

We establish a deconvolutional artificial-neural-network(D-ANN)approach in large-eddy simulation(LES)of compressible turbulent flow.Filtered variables in the neighboring locations are taken as the inputs of D-ANN to recover original(unfiltered)variables,including density,momentum and pressure.The scale-similarity form is adopted to reconstruct subfilter-scale(SFS)terms.The proposed D-ANN models can give better a priori predictions of the sub-filter stress and heat flux than the classical approximate-deconvolution method(ADM)and the velocity-gradient model(VGM).The predicted SFS terms with the D-ANN models have correlation coefficients larger than 98.4%and relative errors smaller than 18%.In the a posteriori analysis,the D-ANN model compares against the implicit LES(ILES),the dynamic-Smagorinsky model(DSM),and the dynamic-mixed model(DMM).The D-ANN model predicts better than these classical models for velocity spectra,statistical properties of SFS kinetic energy flux and velocity increments.The turbulence statistics and transient velocity divergence are also accurately reconstructed.The type of explicit filter and the impact of compressibility do not significantly affect a posteriori accuracy of the D-ANN model.Results showthat the proposed D-ANN approach has a great potential in developing highly accurate SFS models for large-eddy simulation of complex compressible turbulent flow.

关键词： Subfilter-scale model Large-eddy simulation Artificial neural network Machine learning Compressible turbulence

Effects of Prandtl number in two-dimensional turbulent convection

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Chinese Physics B 2021年第9期30卷 290-296页

作者：何建超方明卫高振源黄仕迪包芸 School of Aeronautics and Astronautics Sun Yat-sen UniversityGuangzhou 510275China Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering Southern University of Science and TechnologyShenzhen 518055China Guangdong Provincial Key Laboratory of Turbulence research and Applications Southern University of Science and TechnologyShenzhen 518055China

We report a numerical study of the Prandtl-number(Pr)effects in two-dimensional turbulent Rayleigh-Bénard convection.The simulations were conducted in a square box over the Pr range from 0.25 to 100 and over the Rayleigh number(Ra)range from 10^(7) to 10^(10).We find that both the strength and the stability of the large-scale flow decrease with the increasing of Pr,and the flow pattern becomes plume-dominated at high Pr.The evolution in flow pattern is quantified by the Reynolds number(Re),with the Ra and the Pr scaling exponents varying from 0.54 to 0.67 and-0.87 to-0.93,respectively.It is further found that the non-dimensional heat flux at small Ra diverges strongly for different Pr,but their difference becomes marginal as Ra increases.For the thermal boundary layer,the spatially averaged thicknesses for all the Pr numbers can be described byδθ~Ra^(-0.30) approximately,but the local values vary a lot for different Pr,which become more uniform with Pr increasing.

关键词： turbulent convection Prandtl number direct numerical simulations(DNS)

Inverse design of mesoscopic models for compressible flow using the Chapman-Enskog analysis

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Advances in Aerodynamics 2021年第1期3卷 86-110页

作者： Tao Chen Lian-Ping Wang Jun Lai Shiyi Chen State Key Laboratory for Turbulence and complex Systems College of engineeringPeking University100871 BeijingP.R.China Guangdong Provincial Key Laboratory of Turbulence research and Applications Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace EngineeringSouthern University of Science and Technology518055 ShenzhenP.R.China department of Mechanical engineering University of Delaware19716-3140 NewarkDEUSA.

In this paper,based on simplified Boltzmann equation,we explore the inverse-design of mesoscopic models for compressible flow using the Chapman-Enskog analysis.Starting from the single-relaxation-time Boltzmann equation with an additional source term,two model Boltzmann equations for two reduced distribution functions are obtained,each then also having an additional undetermined source term.Under this general framework and using Navier-Stokes-Fourier(NSF)equations as constraints,the structures of the distribution functions are obtained by the leading-order Chapman-Enskog analysis.Next,five basic constraints for the design of the two source terms are obtained in order to recover the NSF system in the continuum limit.These constraints allow for adjustable bulk-to-shear viscosity ratio,Prandtl number as well as a thermal energy source.The specific forms of the two source terms can be determined through proper physical considerations and numerical implementation requirements.By employing the truncated Hermite expansion,one design for the two source terms is proposed.Moreover,three well-known mesoscopic models in the literature are shown to be compatible with these five constraints.In addition,the consistent implementation of boundary conditions is also explored by using the Chapman-Enskog expansion at the NSF order.Finally,based on the higher-order Chapman-Enskog expansion of the distribution functions,we derive the complete analytical expressions for the viscous stress tensor and the heat flux.Some underlying physics can be further explored using the DNS simulation data based on the proposed model.

关键词： Mesoscopic CFD methods Boltzmann equation Inverse design The Navier-Stokes-Fourier system Chapman-Enskog analysis Structure of distribution function Thermal forcing Boundary condition Bulk viscosity Prandtl number

Lewis数和Karlovitz数对湍流动能和拟能输运方程的影响

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Acta Mechanica Sinica 2022年第7期38卷 29-44,I0001页

作者：李树洲刘晓宇戴鹏陈正 Abouelmagd Abdelsamie 万敏平 Guangdong Provincial Key Laboratory of Turbulence research and Applications Department of Mechanics and Aerospace EngineeringSouthern University of Science and TechnologyShenzhen518055China department of mechanics and engineering Science College of EngineeringPeking UniversityBeijing100871China Laboratory of Fluid Dynamics and Technical flows University of Magdeburg“Otto von Guericke”Magdeburg39106Germany National center for Applied Mathematics Shenzhen Shenzhen518055China

本文通过考虑复杂化学的三维直接数值模拟(DNS),研究了氢火焰(Lewis数约为0.4)和十二烷火焰(Lewis数约为4.2)中的湍动能(TKE)与拟涡能输运方程的统计行为.算例中,Karlovitz(Ka)数在4到150之间,涉及薄反应区和破碎反应区.对湍动能与拟涡... 详细信息

本文通过考虑复杂化学的三维直接数值模拟(DNS),研究了氢火焰(Lewis数约为0.4)和十二烷火焰(Lewis数约为4.2)中的湍动能(TKE)与拟涡能输运方程的统计行为.算例中,Karlovitz(Ka)数在4到150之间,涉及薄反应区和破碎反应区.对湍动能与拟涡能输运方程进行了收支分析,并重新验证了过往文献中的标度项.高Ka数下,粘性耗散项是湍动能平衡中最重要的项,而拟涡能输运方程中的主导项则是粘性耗散项与涡拉伸项,这一性质与薄反应区火焰相似.湍动能输运方程中的速度-压强梯度项和平均速度膨胀项,以及拟涡能输运方程中的膨胀项则受Lewis数的影响.本文提出了受Lewis数影响项的修正标度估计,以解释不同燃烧状态下的Lewis数效应.这项工作表明,Kolmogorov的第一假设并不适用于本文所研究的低Ka数火焰,这类火焰中涡拉伸项与粘性耗散项并不与局部耗散率与粘性呈比例关系.当Ka数足够高时,涡量可以用Kolmogorov时间尺度来衡量,平均拟涡能值接近均匀各向同性的非反应湍流,但较低的Lewis数的燃料需要更高的Ka数才能实现这一点.

关键词：输运方程湍流动能氢火焰燃烧状态标度十二烷耗散率时间尺度

Critical velocity in phosphorus exchange processes across the sediment-water interface

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Journal of Environmental Sciences 2013年第10期25卷 1966-1971页

作者： Jun Wan Ze Wang Zhijie Li Huiling Duan HezhongYuan State Key Laboratory for Turbulence and complex System Department of Mechanics and Aerospace EngineeringCollege of Engineering Peking University College of mechanics and Materials Hohai University research center for Eco-Environmental Sciences Chinese Academy of Sciences School of Life Sciences Nanjing University

Sediments are ultimate sinks of nutrients in lakes that record the pollution history evolutionary processes, and anthropogenic activities of a lake. However, sediments are considered as inner sources of environmental factor changes such as the variation in hydrodynamic conditions because of the nutrients they release. How does this process happen？ This study investigates a typical nutrient phosphorus （P） exchange among sediment, suspended particle matter （SPM）, and water. Compared with numerical and experimental studies, this study confirms that the critical velocity that occurs at a lower flow rate state exists in the range of 7 to 15 crn/sec. Critical velocity below the critical flow rate promotes the migration of particulate phosphorus （PP） to the SPM. On the other hand, critical velocity above the critical flow rate promotes the release of PP in water.

关键词： abrupt expansion flow critical velocity lake eutrophication phosphorus exchange

A Comprehensive Review on Multi-Dimensional Heat Conduction of Multi-Layer and Composite Structures:Analytical Solutions

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Journal of Thermal Science 2021年第6期30卷 1875-1907页

作者： AMIRI DELOUEI Amin EMAMIAN Amin SAJJADI Hasan ATASHAFROOZ Meysam LI Yueming WANG Lian-Ping JING Dengwei XIE Gongnan department of Mechanical engineering University of BojnordBojnordIran Mechanical engineering department Shahrood University of TechnologyShahroodIran department of Mechanical engineering Siijan University of TechnologySiijanIran School of aerospace engineering Xi’an Jiaotong UniversityXi’an 710049China Guangdong Provincial Key Laboratory of Turbulence research and Applications Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace EngineeringSouthern University of Science and TechnologyShenzhen 518055China department of Mechanical engineering University of DelawareNewarkDelaware19711USA International research center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049China department of Mechanical and Power engineering Northwestern Polytechnical UniversityXi'an 710072China

Heat conduction in multi-layer and composite materials is one of the fundamental heat transfer problems in many industrial applications.Due to different materials types,interface conditions,and various geometries of these laminates,the heat conduction mechanism is more complicated than that of one-layer isotropic media.Analytical solutions are the best ways to study and understand such problems in depth.In this study,different existing analytical solutions for heat conduction in multi-layer and composite materials are reviewed and classified in rectangular,cylindrical,spherical,and conical coordinates.Applied boundary conditions,internal heat source,and thermal contact resistance as the most critical parameters in the solution complexity investigated in the literature,are discussed and summarized in different tables.Various types of multi-layer structures such as isotropic,anisotropic,orthotropic,and reinforced laminates are included in this study.It is found that although more than half a century has passed since the beginning of the research on heat transfer in multi-layer composites,new researches that can help with a better understanding in this area are still being offered.The challenges and shortcomings in this area are also discussed to guide future researches.

关键词： multi-dimensional heat conduction composite laminates multi-layer structures analytical solutions interface contact resistance

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被动标量湍流的约束亚格子模型

Acta Mechanica Sinica 2023年第4期39卷 184-194页

作者：黄鹏陈宽宇彭怀午 Hsu-Chew Lee 史一蓬肖左利陈十一万敏平 Guangdong Provincial Key Laboratory of Turbulence research and Applications Department of Mechanics and Aerospace EngineeringSouthern University of Science and TechnologyShenzhen518055China Guangdong-Hong Kong-Macao Joint Laboratory for Data-Driven Fluid mechanics and engineering Applications Southern University of Science and TechnologyShenzhen518055China State Key Laboratory for Turbulence and complex System College of EngineeringPeking UniversityBeijing100871China Northwest Survey and Design research Institute Xi’an710065China Eastern Institute for Advanced Study Ningbo315200China

本文采用约束大涡模拟(C-LES)模型来模拟湍流中的被动标量.通过施加一个基于被动标量大涡模拟(LES)中标量方差通量标度不变量的物理约束来计算动态混合非线性模型(MNLM)的系数.将约束亚格子(SGS)模型与不同的SGS模型在不可压各向同性湍... 详细信息

本文采用约束大涡模拟(C-LES)模型来模拟湍流中的被动标量.通过施加一个基于被动标量大涡模拟(LES)中标量方差通量标度不变量的物理约束来计算动态混合非线性模型(MNLM)的系数.将约束亚格子(SGS)模型与不同的SGS模型在不可压各向同性湍流被动标量中进行比较.此外,C-LES模型减少了SGS标量方差通量在惯性-对流尺度以及较大的黏性-扩散尺度上的变化.先验测试表明,C-LES模型在预测SGS标量通量的方向和大小方面表现最好.此外,C-LES模型减少了SGS标量方差通量在惯性-对流范围内以及粘性-扩散范围内大尺度的变化.在后验测试中,与传统的动态Smagorinsky(DSM)和MNLM模型相比,C-LES模型在预测标量谱和内部间歇性的演变中表现明显更好.这些结果表明,在SGS模型中施加物理约束是在被动标量湍流大涡模拟中的一种有前途的方法.

关键词： SGS模型亚格子模型 LES模型各向同性湍流物理约束扩散范围非线性模型动态混合