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Particle size distribution of bed materials in the sandy river bed of alluvial rivers

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International Journal of Sediment Research 2017年第3期32卷 331-339页

作者： Luohao zhang hongwu zhang hongwu Tang Chensu Zhao College of Water Conservancy and Hydropower Engineering Hohai University State Key Laboratory of Hydroscience and Engineering Tsinghua University School of Civil and Environment Engineering University of Science and Technology Beijing

The particle size distribution of bed materials in the sandy river bed of alluvial rivers is important in the study of topics such as friction, river bed evolution, erosion, and siltation. It also can reflect the dependency relation between river bed sediment and flow intensity. In this paper, the critical pattern of sediment movement in the near-wall region of a sandy river bed was analyzed. According to the principle of momentum balance, the critical settling-rising condition of bed material in a sandy river bed was found to be instantaneous turbulent velocity equal to 2.7 times the sediment settling velocity in quiescent water. Based on a vertical instantaneous turbulent velocity with a Gaussian distribution, a theoretical relation for calculating the particle size distribution of bed materials in a sandy river bed without pre-known characteristic grain sizes was developed by solving a stochastic equation. The formula is verified using measured data, and the results show that the proposed formula was in accordance with the measured data. This study has theoretical significance and practical value for determining the bed material particle size distribution of the sandy bed of alluvial rivers.

关键词： Particle size distribution Bed material Turbulence Momentum Sandy river bed

A CONCURRENT MULTISCALE METHOD FOR SIMULATION OF CRACK PROPAGATION

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Acta Mechanica Solida Sinica 2015年第3期28卷 235-251页

作者： Jingkai Wu hongwu zhang Yonggang Zheng State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering MechanicsFaculty of Vehicle Engineering and Mechanics Dalian University of Technology Nanjing Research Institute of Electronics Technology

A concurrent multiscale method is developed for simulating quasi-static crack propagation in which the failure processes occur in only a small portion of the structure. For this purpose, a multiscale model is adopted and both scales are discretized with finite-element meshes. The extended finite element method is employed to take into account the propagation of discontinuities on the fine-scale subregions. At the same time, for the other subregions, the coarse-scale mesh is employed and is resolved by using the extended multiscale finite element method. Several representative numerical examples are given to verify the validity of the method.

关键词： concurrent multiscale method crack propagation extended finite element method level set method

Solving frictional contact problems by two aggregate-function-based algorithms

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Acta Mechanica Sinica 2005年第5期21卷 467-471页

作者： Suyan He hongwu zhang Xingsi Li Department of Engineering Mechanics State Key Laboratory of Structural Analysis of Industrial EquipmentDalian University of Technology Dalian 116024 China School of Software Dalian University of Foreign LanguagesDalian 116002 China

Three dimensional frictional contact problems are formulated as linear complementarity problems based on the parametric variational principle. Two aggregate-functionbased algorithms for solving complementarity problems are proposed. One is called the self-adjusting interior point algorithm, the other is called the aggregate function smoothing algorithm. Numerical experiment shows the efficiency of the proposed two algorithms.

关键词： Frictional contact problem. Linear complementarity problem .Aggregate function ~ Interior pointalgorithm ~ Smoothing algorithm

Bright yellow-emitting long persistent luminescence from Mn^(2+)-activated strontium aluminate phosphor

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Journal of Rare Earths 2022年第7期40卷 1029-1036页

作者： Wenzhi Sun Tao Tan Jize Cai hongwu zhang School of Chemistry and Materials Science Ludong UniversityYantai 264025China State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China

We developed bright yellow-emitting long persistent luminescence(LPL)materials Sr_(4)Al_(14)O_(25):Mn^(2+)and Sr_(4)Al_(14)O_(25):Mn^(2+),N(N=Zr^(4+),Ho^(3+),Er^(3+))by high temperature solid-state *** addition of Zr^(4+),Ho^(3+)and Er^(3+)can regulate trap distributions and improve energy storage ability of the *** LPL perfo rmance of SAO:Mn^(2+),Ho^(3+)is optimal,considering LPL intensity and duration *** LPL of SAO:Mn^(2+),Ho^(3+)can be observed for 3 h by naked eyes in dark after removing the excitation *** of LPL spectra are different from those of PL,because the two types of Mn^(2+)centers do not play equal parts in LPL and photoluminescence(PL).Trap depths of TL peaks centered at 354 K(peak 1)and 455 K(peak 2)are 0.60 and 0.72 eV,*** peak 1 at 354 K is the effective TL peak responsible for *** SAO:Mn^(2+),Ho^(3+),Mn^(2+)ions doped in Al^(3+)sites serve as emitting centers,and positively charged HoSr defects are the main effective trap ***,a feasible LPL mechanism of SAO:Mn^(2+),Ho^(3+)was proposed to clarify the generation process of LPL.

关键词： Long persistent phosphors Sr_(4)Al_(14)O_(25):Mn^(2+) Trap distributions Afterglow mechanism Rare earths

A NOTE FOR ANALYSIS OF THERMOMECHANICAL CONTACT PROBLEMS

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Acta Mechanica Solida Sinica 2002年第4期15卷 303-311页

作者： zhang hongwu Huang Hui Dalian Univ Technol Dept Engn Mech State Key Lab Struct Anal Ind Equipment Dalian 116024 Peoples R China

A discussion about the bifurcation and non-uniqueness of solutions in theanalysis of thermo-mechanical contact problems with initial gap is given. Without loss ofgenerality, a mechanical contact problem coupled with steady heat transfer is studied and an exampleof non-uniqueness of solutions caused by the thermo-mechanical mechanism is presented. Theimportant work is that the non-uniqueness of solutions, which is different from that found in theanalysis of the traditional frictional contact problems, is studied in detail. The possibleoscillation and non-convergence problems in the iteration process of the numerical computation arediscussed, and an enhanced algorithm is put forward to overcome the difficulties.

关键词： heat transfer contact analysis non-uniqueness of solutions

Influence of Hub Contouring on the Performance of a Transonic Axial Compressor Stage with Low Hub-Tip Ratio

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Journal of Thermal Science 2022年第1期31卷 179-188页

作者： LI Xinlong LIU Shuaipeng GENG Shaojuan zhang hongwu Advanced Gas Turbine Laboratory Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China Innovation Academy for Light-Duty Gas Turbine Chinese Academy of SciencesBeijing 100190China Key Laboratory of Advanced Energy and Power Chinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

The rotor blade height with low hub-tip ratio is relatively longer,and the aerodynamic parameters change drastically from hub to *** the organization of flow field at hub becomes more *** paper takes a transonic 1.5-stage axial compressor with low hub-tip ratio as the research *** influence of four types of rotor hub contouring on the performance of transonic rotor and stage is explored through numerical *** three-dimensional numerical simulation results show that different hub contourings have obvious influence on the flow field of transonic compressor rotor and stage,thus affecting the compressor *** detailed comparison is conducted at the rotor peak efficiency point for each hub *** with the linear hub contouring,the concave hub contouring can improve the flow capacity,improve the rotor working capacity,and increase the flow *** flow field near blade root and efficiency of transonic rotor is *** convex hub contouring will reduce the mass flow rate,pressure ratio and efficiency of the transonic *** consideration should be given to the influence of stator flow field by hub contouring.

关键词： transonic compressor low hub-tip ratio hub contouring aerodynamics performance numerical simulation

MIXED ENERGY METHOD FOR SOLUTION OF QUADRATIC PROGRAMMING PROBLEMS AND ELASTIC-PLASTIC ANALYSIS OF TRUSS STRUCTURES

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Acta Mechanica Solida Sinica 2002年第1期15卷 1-8页

作者： Zhong Wanxie zhang hongwu Dalian Univ Technol Dept Mech Engn State Key Lab Struct Anal Ind Equipment Dalian 116024 Peoples R China

A new algorithm for the solution of quadratic programming problemsis put forward in terms of the mixed energy theory and is furtherused for the incremental solution of elastic-plastic trussstructures. The method proposed is different from the traditionalone, for which the unknown variables are selected just in one classsuch as displacements or stresses. The present method selects thevariables in the mixed form with both displacement and stress. As themethod is established in the hybrid space, the information found inthe previous incremental step can be used for the solution of thepresent step, making the algorithm highly effi- cient in thenumerical solution process of quadratic programming problems. Theresults obtained in the exm- ples of the elastic-plastic solution ofthe truss structures verify what has been predicted in thetheoretical anal- ysis.

关键词： elastic-plastic analysis mixed energy method quadratic programming problem

Numerical Simulation on Unsteady Flow Mechanism of a 1.5-Stage Axial Transonic Compressor

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Journal of Thermal Science 2024年第5期33卷 1851-1866页

作者： PENG Shuxuan zhang Xiaoyu WANG Wentao zhang hongwu LI Xinlong High Efficiency and Low Carbon Gas Turbine Digitalization Research Centre Nanjing Institute of Future Energy SystemNanjing 211135China Advanced Gas Turbine Laboratory Institute of Engineering ThermophysicsChinese Academy of SciencesBeijing 100190China Key Laboratory of Advanced Energy and Power Chinese Academy of SciencesBeijing 100190China Innovation Academy for Light-Duty Gas Turbine Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China BYD Auto Industry Company Limited Shenzhen 518116China

In this paper,a numerical simulation method is used to calculate a 1.5-stage axial transonic compressor to explore its unsteady flow *** performance curve is compared with the experimental data to verify the calculation method with a high numerical accuracy,which shows that the unsteady calculation has good *** to the analysis of the data from the monitoring points under the near-stall condition,the unsteady disturbances originate from the tip region of blade and perform the strongest at the blade pressure surface with a broadband *** analysis is conducted by combining with the characteristics of the transient flow field at the tip of *** results show that the unsteady pressure fluctuations are caused by the migration of the new vortex *** new vortex cores are generated by the breakdown of leakage vortex in the downstream,which is induced by the leakage vortex and shock wave ***,the relationship between the unsteady flow characteristics and the working conditions is also *** leakage vortex intensity and the shock wave strength gradually increase with the decrease of flow *** the combination of the leakage vortex intensity and shock wave strength reaches the first threshold,a single frequency of unsteady disturbances appears at the blade *** the combination of the leakage vortex intensity and shock wave strength reaches the second threshold,the frequency of unsteady disturbances changes to a broadband.

关键词： numerical simulation axial transonic compressor unsteady flow vortex breakdown

The Response of a Low Speed Compressor on Rotating Inlet Distortion

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Journal of Thermal Science 2006年第4期15卷 314-318页

作者： Chaoqun NIE Jingxuan zhang Zhiting TONG hongwu zhang Institute of Engineering Thermophysics Chinese Academy of Sciences Graduate School Chinese Academy of Sciences Beijing 100080 China

In multi-spool engines, the downstream compressor experiences a rotating inlet distortion if rotating stall occurs in upstream compressor, which may induce the instability of the whole compressor. In this paper, the compressor dynamic behavior is the major focus. The experiment was carried out on a single-stage low-speed axial-flow compressor. A rotating distortion generator equipped with different distortion sector（s） was designed to produce different rotating inlet distortion clockwise or counterclockwise with up to 100% of the compressor design speed. The distortion sector can be installed single or in some combination such as four sectors together. Three types of distortion sector/combination are used in the research work, which are single 30 degree sector, four 30 degree sec- tors and single 120 degree sector. It is found that the total pressure loss caused by rotating sector（s） increases when the distortion speed rises. For co-rotating distortions, all the three types of inlet distortion exhibited a peak in stall margin degradation when the distortion speed corresponded to roughly 50% of rotor speed. The two-dimensional numerical simulations of the compressor flow field clearly show the propagation of the distur- bances trigged by the distortion sector（s）.

关键词： distortion compressor stall margin