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On the analytical solution of transient friction in channel flows

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Applied Mathematics and Mechanics(English Edition) 2024年第8期45卷 1447-1466页

作者： f.j.GARCíA-GARCíA p.fARINAS-ALVARINO Department of Naval&Industrial Engineering Polytechnic School of EngineeringUniversity of A CorunaCampus Industrial de FerrolFerrol 15403A CorunaSpain Integraciones Técnicas de Seguridad S.A.Pol.Ind.Espiritu SantoC/Nobel15Cambre 15650A CorunaSpain

The transient friction in channel mean flows is the sum of two contributions,i.e.,the underlying laminar flow(ULf)and the purely turbulent component(pTC),and the contributions are analyzed separately by theoretical *** is found that,the transient friction may be higher or remarkably lower than that in equal-Reynolds number steady-state *** universal time constant for plane-parallel laminar flows is reported,and the role of the time constant in a turbulent mean flow is *** is shown that the time constant is related to the turbulence's frozen ***,a study of the logarithmic layer during the transient flow is accomplished,which shows that the logarithmic layer is destroyed.

关键词： transient friction transient flow unsteady channel flow

Comeld^TM joints: A Novel Technique for Bonding Composites and Metal

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稀有金属材料与工程 2009年第A3期38卷 134-141页

作者： Tu W Guild f j Hogg p j Queen Mary University of London Imperial College London South Kensington Campus University of Manchester PO Box 88

Current and future structural applications for composite laminates frequently involve design solutions combining composite laminates and metal; the materials must be joined. Two conventional means of joining are available mechanical joining and adhesive bonding. Both methods have critical disadvantages. A novel surface treatment for metals developed at TWI, Surfi-Sculpt, leads to the formation of surface protrusions on metal surfaces. These protrusions are typically 1.0 mm high and 0.6 mm in diameter. The surface modified metal can be bonded with composite laminates to form a Comeld～TM joint. These joints can be described as a combination of mechanical fastening and adhesive bonding. This paper describes our current work using finite element modelling to optimize the protrusions in respect to their geometry and distribution. The simulations require multi-scale modelling techniques to transfer results between the global model of the whole joint and the unit cell models containing a protrusion. Results from the simulations show critical effects on stress distributions arising from changing protrusion geometry. These joints show significant advantages over conventional adhesive joining technologies and their application would allow improved performance for combinations of metal and composite laminates.

关键词：复合材料金属表面处理技术物理性能

A dive into spectral inference networks: improved algorithms for self-supervised learning of continuous spectral representations

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Applied Mathematics and Mechanics(English Edition) 2023年第7期44卷 1199-1224页

作者： j.WU S.f.WANG p.pERDIKARIS Graduate Group in Applied Mathematics and Computational Science University of Pennsylvania PhiladelphiaPA 19104U.S.A. Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania PhiladelphiaPA 19104U.S.A.

We propose a self-supervising learning framework for finding the dominant eigenfunction-eigenvalue pairs of linear and self-adjoint *** represent target eigenfunctions with coordinate-based neural networks and employ the fourier positional encodings to enable the approximation of high-frequency *** formulate a self-supervised training objective for spectral learning and propose a novel regularization mechanism to ensure that the network finds the exact eigenfunctions instead of a space spanned by the ***,we investigate the effect of weight normalization as a mechanism to alleviate the risk of recovering linear dependent modes,allowing us to accurately recover a large number of *** effectiveness of our methods is demonstrated across a collection of representative benchmarks including both local and non-local diffusion operators,as well as high-dimensional time-series data from a video *** results indicate that the present algorithm can outperform competing approaches in terms of both approximation accuracy and computational cost.

关键词： spectral learning partial differential equation(pDE) neural network slow features analysis

Numerical Simulation of the Tip Aerodynamics and Acoustics Test

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journal of Thermal Science 2016年第2期25卷 153-160页

作者： f Tejero E p Doerffer O Szulc j L Cross The Szwalski Institute of fluid-flow Machinery Polish Academy of Sciences. Fiszera 14 80-231 Gdansk Poland NASA Ames Research Center (retired) Moffett Field CA USA

The application of an efficient flow control system on helicopter rotor blades may lead to improved aerodynamic performance. Recently, our invention of Rod Vortex Generators(RVGs) has been analyzed for helicopter rotor blades in hover with success. As a step forward, the study has been extended to forward flight conditions. for this reason, a validation of the numerical modelling for a reference helicopter rotor(without flow control) is needed. The article presents a study of the flow-field of the AH-1G helicopter rotor in low-, medium- and high-speed forward flight. The CfD code fLOWer from DLR has proven to be a suitable tool for the aerodynamic analysis of the two-bladed rotor without any artificial wake modelling. It solves the URANS equations with LEA(Linear Explicit Algebraic stress) k-ω model using the chimera overlapping grids technique. Validation of the numerical model uses comparison with the detailed flight test data gathered by Cross j. L. and Watts M. E. during the Tip Aerodynamics and Acoustics Test(TAAT) conducted at NASA in 1981. Satisfactory agreements for all speed regimes and a presence of significant flow separation in high-speed forward flight suggest a possible benefit from the future implementation of RVGs. The numerical results based on the URANS approach are presented not only for a popular, low-speed case commonly used in rotorcraft community for CfD codes validation but preferably for medium- and high-speed test conditions that have not been published to date.

关键词： AH-1G TAAT helicopter rotor forward flight chimera overlapping grid

A new thermodynamically stable Nb_(2)Ni intermetallic compound phase revealed by peritectoid transition within binary Nb-Ni alloy system

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journal of Materials Science & Technology 2022年第5期100卷 246-253页

作者： j.f.Zhao H.p.Wang B.Wei School of physical Science and Technology Northwestern Polytechnical UniversityXi’an 710072China

A new intermetallic compound of thermodynamically stable Nb_(2)Ni phase is discovered within Nb-Ni binary system,refreshing the current situation that there are only three stable intermediate phases of Nb_(7)Ni_(6),NbNi_(3) and NbNi_(8).The new stable phase is generated from the peritectoid transition:(Nb)+Nb_(7)Ni_(6)→Nb_(2)Ni,and the transformation temperature is 1533 *** refreshes the current equilibrium Nb-Ni binary phase *** is confirmed by transmission electron microscopy and the annealing experiments,which is determined to be the fCC structure(pearson:cf96,space grope:fd-3m O2,a=11.888A).furthermore,the equilibrium properties of Nb_(2)Ni phase are produced by density functional theory,including the formation energy,cohesive energy,bulk modulus and lattice constant.

关键词： Intermetallic compound peritectoid transition Transmission electron microscopy Density functional theory Nb alloy

Influence of Turbulators in Blade Cooling passages on film Hole Discharge Coefficients

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journal of Thermal Science 2004年第3期13卷 245-254页

作者： H.-p. SCHIffER j. TAEGE f. HASELBACH Rolls-Royce Deutschland Eschenweg 11 D-15827 Dahlewitz GermanyRolls-Royce Deutschland Eschenweg 11 D-15827 Dahlewitz GermanyRolls-Royce Deutschland Eschenweg 11 D-15827 Dahlewitz Germany

This paper details the results of a joint project between Rolls-Royce Deutschland (RRD) and the Northwestern polytechnical University of China (NWpU). The objective of the project was the determination of the influence of tabulators in turbine blade cooling passages on film hole discharge coefficients (Cd coefficients). A large-scale plexiglas model was used by the NWpU to measure the turbulator influence on Cd coefficients for a wide range of different geometrical parameters, Reynolds numbers and cooling flow off take ratios. RRD specified the comprehensive test matrix and analysed the test data. The CfD code fLUENT was used by RRD for numerical simulation of the test cases with the main objective to support the interpretation of observed trends. Both, experimental and numerical results will be presented in this paper for a selection of test configurations.

关键词： film hole discharge coefficient turbulator blade cooling.

friction and wear behaviors of a gradient nano-grained AISI 316L stainless steel under dry and oil-lubricated conditions

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journal of Materials Science & Technology 2018年第10期34卷 1835-1842页

作者： p.f. Wang Z. Han Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China University of Chinese Academy of Sciences Beijing 100049 China

A gradient nano-grained （GNG） surface layer was fabricated on an AIS1316L stainless steel （SS） by using the surface mechanical rolling treatment （SMRT）. Reciprocating dry and oil-lubricated sliding tests of the GNG 316L SS in air at room temperature were conducted in comparison with the coarse-grained （CG） counterpart. Worn surface morphologies and subsurface microstructures were investigated for both 316L SS samples. 316L SS with a GNG surface layer shows a significantly improved wear resistance, especially under oil-lubricated condition. The notably wear resistance enhancement of the GNG 316L SS is attributed to the GNG surface layer with high strain accommodation ability and high hardness, which can reduce the wear volume in the running-in stage effectively.

关键词： Austenitic stainless steel Gradient nano-grained surface layer friction and wear Running-in

A Comparative in vitro Study on Biomedical Zr-2.5X(X=Nb,Sn) Alloys

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journal of Materials Science & Technology 2014年第4期30卷 299-306页

作者： f.Y.Zhou K.j.Qiu D.Bian Y.f.Zheng j.p.Lin Centre for Biomedical Materials and Engineering Harbin Engineering University Department of Materials Science and Engineering College of EngineeringPeking University State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing

Nb and Sn are major alloying elements in Zr alloys. In this study, the microstructure, mechanical properties, corrosion behavior, cytocompatibility and magnetic resonance imaging （MRI） compatibility of Zr-2.5X （X = Nb, Sn） alloys for biomedical application are comparatively investigated. It is found that Zr-2.5Nb alloy has a duplex structure of ~ and ~ phase and Zr-2.5Sn alloy is composed of α phase. Both separate addition of Nb and Sn can strengthen Zr but Nb is more effective in strengthening Zr than Sn. The studied Zr-2.5X （X = Nb, Sn） alloys show improved corrosion resistance compared to pure Zr as indicted by the decreased corrosion current density. The alloying addition of Nb enhances the pitting resistance of Zr, whereas the addition of Sn decreases the pitting resistance of Zr. The extracts of Zr-2.5X alloys produce no significant deleterious effect on fibroblast cells （L-929） and osteoblast-Iike cells （MG 63）, indicating good in vitro cytocompatibility. The Zr-2.5X （X = Nb, Sn） alloys show decreased magnetic susceptibility compared to pure Zr and their magnetic susceptibility is far lower than that of pure Ti and Ti-6AI-4V alloy. Based on these facts, Zr-2.5Nb alloy is more suitable for implant material than Zr-2.5Sn alloy. Sn is not suitable as individual alloying addition for Zr because Sn addition decreases the pitting resistance in physiological solution.

关键词： Zr alloys Mechanical properties Corrosion resistance Cytocompatibility Magnetic susceptibility

Sensory quality of meat from eight different types of cattle in relation with their biochemical characteristics

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journal of Integrative Agriculture 2016年第7期15卷 1550-1563页

作者： M Gagaoua E M C Terlouw D Micol j-f Hocquette a.p.moloney K Nuernberg D Bauchart A Boudjellal N D Scollan R I Richardson B picard INRA UMRH 1213Unite de Recherches sur les HerbivoresTheix63122 Saint Genes ChampanelleFrance VetAgro Sup UMRH 1213Unite de Recherches surles HerbivoresTheix63122 Saint Genes ChampanelleFrance Equipe Maquav INA TAAUniversite Freres Mentouri ConstantineRoute de Ain El-Bey25000 ConstantineAlgeria Teagasc Animal and Grassland Research and Innovation CentreGrangeDunsanyCo.MeathIreland fBN Leibniz Institute for farm Animal Biology W-StahI-Allee 218196 DummerstorfGermany Institute of Biological Environmental and Rural Sciences(IBERS)Aberystwyth UniversityGogerddanAberystwyth SY23 3EBUnited Kingdom Division of farm Animal Science University of BristolLangford HouseBristol BS40 5DUUnited Kingdom

The present study compared eight breeds of cattle differing in gender （heifers, buls and steers） to determine associations between muscle characteristics and meat sensory qualities of theLongissimus thoracis muscle. Animal types differed in al the muscle characteristics and sensory qualities. Many correlations among muscle characteristics and among sensory qualities were consistent for most animal types. Isocitrate dehydrogenase （ICDH） activities alowed discrimination of muscles with respect to myosin heavy chain （MyHC）-I proportions for al animal types. Lactate dehydrogenase （LDH） and phos-phofructokinase （pfK） activities were positively correlated for most animal types. Overal liking was correlated with beef lfavour and abnormal lfavour in al animal types and with global tenderness for al animal types except for Charolais cross breed steers. for al animal types except for Angus×friesian heifers, beef lfavour and abnormal lfavour were negatively correlated. Overal liking was not correlated with juiciness. pfK, ICDH and citrate synthase （CS） activities were strongly associated with tenderness, beef lfavour and overal liking when average values for al animal types were used. However, associations between muscle characteristics and sensory qualities within animal types were weak and inconsistent.

关键词： cattle muscle characteristics meat sensory qualities gender breed prediction