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Interaction of single-pulse laser energy with bow shock in hypersonic flow

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Chinese Journal of Aeronautics 2014年第2期27卷 241-247页

作者： Hong Yanji Wang Diankai Li Qian Ye Jifei State Key Laboratory of Laser Propulsion & Application Equipment Academy

Pressure sensing and schlieren imaging with high resolution and sensitivity are applied to the study of the interaction of single-pulse laser energy with bow shock at Mach 5. An Nd：YAG laser operated at 1.06 μm, 100 mJ pulse energy is used to break down the hypersonic flow in a shock tunnel. Three-dimensional navier-stokes equations are solved with an upwind scheme to simulate the interaction. The pressure at the stagnation point on the blunt body is measured and calculated to examine the pressure variation during the interaction. Schlieren imaging is used in conjunction with the calculated density gradients to examine the process of the interaction, The results show that the experimental pressure at the stagnation point on the blunt body and schlieren imaging fit well with the simulation. The pressure at the stagnation point on the blunt body will increase when the transmission shock approaches the blunt body and decrease with the formation of the rarefied wave. Bow shock is deformed during the interaction. Quasi-stationary waves are formed by high rate laser energy deposition to control the bow shock. The pressure and temperature at the stagna- tion point on the blunt body and the wave drag are reduced to 50%, 75% and 81% respectively according to the simulation. Schlieren imaging has provided important information for the inves- tigation of the mechanism of the interaction.

关键词： Drag Flow control navier-stokes equation Shock wave Wind tunnel test

Performance optimization of grooved slippers for aero hydraulic pumps

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Chinese Journal of Aeronautics 2016年第3期29卷 814-823页

作者： Chen Juan Ma Jiming Li Jia Fu Yongling Department of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China Sino-French Engineer School Beihang UniversityBeijing 100191China AVIC Xi'an Flight Automatic Control Research Institute.Xi'an 710065 China

A computational fluid dynamics （CFD） simulation method based on 3-D navier stokes equation and Arbitrary Lagrangian Eulerian （ALE） method is presented to analyze the grooved slip- per performance of piston pump. The moving domain of grooved slipper is transformed into a fixed reference domain by the ALE method, which makes it convenient to take the effects of rotate speed, body force, temperature, and oil viscosity into account. A geometric model to express the complex structure, which covers the orifice of piston and slipper, vented groove and the oil film, is constructed. Corresponding to different oil film thicknesses calculated in light of hydrostatic equilibrium theory and boundary conditions, a set of simulations is conducted in COMSOL to analyze the pump characteristics and effects of geometry （groove width and radius, orifice size） on these characteristics. Furthermore, the mechanics and hydraulics analyses are employed to validate the CFD model, and there is an excellent agreement between simulation and analytical results. The simulation results show that the sealing land radius, orifice size and groove width all dramatically affect the slipper behavior, and an optimum tradeoff among these factors is conducive to optimizing the pump design.

关键词： Arbitrary LagrangianEulerian (ALE) Computational fluid dynam-ics (CFD) Grooved slipper Hydraulic pump navier-stokes equation Performance analysis

NUMERICAL SIMULATION OF TURBULENT SPOTS IN INCLINED OPEN-CHANNEL FLOW

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Journal of Hydrodynamics 2005年第2期17卷 179-185页

作者： ZHANGLi TANGDeng-bin CollegeofAerospaceEngineering NanjingUniversityofAeronauticsandAstronauticsNanjing210016China

The generation and evolution of turbulent spots in the open-channel flow are simulated numerically by using the navier-stokes equations. An effective numerical method with high accuracy and high resolution is developed. The fourth-order time splitting methods with high accuracy is proposed. Three-dimensional coupling difference methods are presented for the spatial discretization of the Poisson equation of pressure and Hemholtz equations of velocity, therefore, the fourth-order three-dimensional coupling central difference schemes are constituted. The fourth-order explicit upwind-biased compact difference schemes are designed to overcome the difficulty for the general higher-order central difference scheme which is inadaptable in the boundary neighborhood. The iterative algorithm and overall time marching is used to enhance efficiency. The method is applied in the numerical simulation of turbulent spots at various complex boundary conditions and flow domains. The generation and the developing process of turbulent spots are given, and the basic characteristics of turbulent spots are shown by simulating the evolution of the wall pulse in inclined open-channel flow.

关键词： turbulent spot navier-stokes equation numerical simulation three-dimensional coupling difference scheme wall pulse

UPWIND LOCAL DIFFERENTIAL QUADRATURE METHOD FOR SOLVING COUPLED VISCOUS FLOW AND HEAT TRANSFER equationS

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Applied Mathematics and Mechanics(English Edition) 2004年第10期25卷 1130-1138页

作者： A.S.J.Al-Saif 朱正佑 Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

The differential quadrature method (DQM) has been applied successfully to solve numerically many problems in the fluid mechanics. But it is only limited to the flow problems in regular regions. At the same time, here is no upwind mechanism to deal with the convective property of the fluid flow in traditional DQ method. A local differential quadrature method owning upwind mechanism (ULDQM) was given to solve the coupled problem of incompressible viscous flow and heat transfer in an irregular region. For the problem of flow past a contraction channel whose boundary does not parallel to coordinate direction, the satisfactory numerical solutions were obtained by using ULDQM with a few grid points. The numerical results show that the ULDQM possesses advantages including well convergence, less computational workload and storage as compared with the low-order finite difference method.

关键词： upwind locall DQM navier-stokes equation heat equation

Rolling force prediction for strip casting using theoretical model and artificial intelligence

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Journal of Central South University 2010年第4期17卷 795-800页

作者：曹光明李成刚周国平刘振宇吴迪王国栋刘相华 State Key Laboratory of Rolling and Automation Northeastern University

Rolling force for strip casting of 1Cr17 ferritic stainless steel was predicted using theoretical model and artificial *** zone was classified into two parts by kiss point position during casting ***-stokes equation in fluid mechanics and stream function were introduced to analyze the rheological property of liquid zone and mushy zone,and deduce the analytic equation of unit compression stress *** traditional hot rolling model was still used in the solid *** networks based on feedforward training algorithm in Bayesian regularization were introduced to build model for kiss point *** results show that calculation accuracy for verification data of 94.67% is in the range of ±7.0%,which indicates that the predicting accuracy of this model is very high.

关键词： kiss point navier-stokes equation rheological properties Bayesian method generalization capabilities

The validity of the Reynolds equation in spool valve analysis considering cavitation

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Friction 2016年第3期4卷 266-276页

作者： Sung-Ho HONG Kyung-Woong KIM School of Mechanical Aerospace & Systems Engineering Korea Advanced Institute of Science and Technology 291 Daehak-ro Yuseong-guDaejeon 305-701 Republic of Korea

The purpose of this research is to investigate the validity of the Reynolds equation in spool valve analysis under cavitation. This study is carried out for a laminar and isothermal flow between a sleeve and spool with grooves. The pressure and lateral force obtained from the Reynolds equation and the navier-stokes equation are compared with variations of aspect ratio, cross sectional area, and number of grooves. The cavitation phenomenon is considered by using a cavitation model in the navier-stokes equation and the Reynolds cavitation boundary condition in the Reynolds equation. A large difference of more than 20% is found between the equations for a lateral force of spool valve with many grooves. It was found that the Reynolds equation is not suitable for calculation of a lateral force of the spool valve with multiple-grooves of which the width and depth are even larger than the clearance under cavitation.

关键词： validity Reynolds equation navier-stokes equation spool valve cavitation

COMPARISON OF STABILITY BETWEEN navier-stokes AND EULER equationS

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Applied Mathematics and Mechanics(English Edition) 2006年第9期27卷 1257-1263页

作者：施惟慧王曰朋沈春 Department of Mathematics Shanghai University Shanghai 200444 P. R. China Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 P. R. China Department of Mathematics Nanjing University of Information Science & TechnologyNanjing 210044P. R. China School of Mathematics and Information Yantai Normal University Yantai 264025 Shandong Province P. R. China

The stability about navier-stokes equation and Euler equation was brought into comparison. And by taking their typical initial value problem for example, the reason of leading to the difference in stability between Na... 详细信息

关键词： navier-stokes equation Euler equation stable equation singular equation

SECOND-ORDER OPTIMALITY CONDITIONS FOR OPTIMAL CONTROL PROBLEMS GOVERNED BY 3-DIMENSIONAL NEVIER-stokes equationS

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Acta Mathematica Scientia 2006年第4期26卷 729-734页

作者：王丽娟何培杰 Department of Mathematics Wuhan University Wuhan 430072China School of Power and Mechanical Engineering Wuhan University Wuhan 430072China

This article is concerned with second-order necessary and sufficient optimality conditions for optimal control problems governed by 3-dimensional navier-stokes equations. The periodic state constraint is considered.

关键词： Necessary and sufficient optimality conditions optimal control navier-stokes equation periodic state constraint

CONSTRUCTION OF THIRD-ORDER WNND SCHEMEAND ITS APPLICATION IN COMPLEX FLOW

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Applied Mathematics and Mechanics(English Edition) 2005年第1期26卷 35-43页

作者：刘伟赵海洋谢昱飞 College of Aerospace and Material Engineering National University of Defense Technology Changsha 410073 P.R.China China Aerodynamics Research and Development Center MianyangSichuan 621000P.R.China

According to the Liu's weighted idea, a space third-order WNND (weighted non-oscillatory, containing no free parameters, and dissipative scheme) scheme was constructed based on the stencils of second-order NND (non-oscillatory, containing no free parameters, and dissipative scheme) scheme. It was applied in solving linear-wave equation, 1D Euler equations and 3D navier-stokes equations. The numerical results indicate that the WNND scheme which does not increase interpolated point(compared to NND scheme) has more advantages in simulating discontinues and convergence than NND scheme. Appling WNND scheme to simulating the hypersonic flow around lift-body shows:With the AoA(angle of attack) increasing from 0° to 50°, the structure of limiting streamline of leeward surface changes from unseparating,open-separating to separating, which occurs from the combined-point (which consists of saddle and node points). The separating area of upper wing surface is increasing with the (AoA's) increasing. The topological structures of hypersonic flowfield based on the sectional flow patterns perpendicular to the body axis agree well with Zhang Hanxin's theory. Additionally, the unstable-structure phenomenon which is showed by two saddles connection along leeward symmetry line occurs at some sections when the AoA is bigger than 20°.

关键词： high-order scheme numerical simulation topological structure limiting streamline of surface navier-stokes equation WNND scheme