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OPTIMAL ERROR ESTIMATES OF A DECOUPLED SCHEME BASED ON TWO-GRID FINITE ELEMENT FOR MIXED navier-stokes/DARCY MODEL

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Acta Mathematica Scientia 2018年第4期38卷 1361-1369页

作者： Wi QIN Wanren HOU School of Mathematics and Statistics Xi＇an Jiaotong UniversityXi＇an 710049China

Although the two-grid finite element decoupled scheme for mixed navier-stokes/ Darcy model in literatures has given the numerical results of optimal convergence order, the theoretical analysis only obtain the optimal error order for the porous media flow and a non-optimal error order for the fluid flow. In this article, we give a more rigorous of the error analysis for the fluid flow and obtain the optimal error estimates of the velocity and the pressure.

关键词： navier-stokes equation Darcy's law two-grid method optimal error estimate

Multigrid navier-stokes Calculation for Two Dimensional Cascades

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Journal of Thermal Science 1998年第1期7卷 16-21页

作者： YangCe LaoDazhong 等 ThermalEngineeringDepartment TsinghuaUniversityBeijing100084China ThermalEngineeringDepartment Tsi

A fast and accurate numerical method for solving the two dimensional Reynolds aveaged navier stokes is applied to calculate the internal fluid of turbines and compressors. The code is based onan explicit, time-marching, finite volume technique. In order to accelerate convergence, local time stepping, multigrid method is employed. Four stage Runge-Kutta method is implemented to extend the stability domain. Test cases of Hobson’s impulse cascade, NASA Rotor 37 and Sanz’s supercritical compressor cascade are presented. Results of Mach number distribution on blade surfaces and Mach number contour plots indicate good agreement with experimental data. Compared with full three 3D navier-stokes (N-S) codes, the two dimensional code only takes a short time to obtain predicted results. This code can be used widely in practical engineering design.

关键词： numerical method two dimension navier-stokes equation turbomachinery

navier-stokes Computation of Grid Fin Missile Using Hybrid Structured-Unstructured Grids

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Chinese Journal of Aeronautics 2006年第4期19卷 304-308页

作者：邓有奇马明生郑鸣周乃春 Beijing University of Aeronautics and Astronautics Beijing 100083 China China Aerodynamics Research & Development Center Mianyang 621000 China Northwestern Polytechnical University Xi'an 710072 China China Aerodynamics Research & Development Center Mianyang 621000 Chin China Aerodynamics Research & Development Center Mianyang 621000 China

Viscous CFD computations are performed to predict the aerodynamic coefficients and flowfield for a missile with grid fins by using hybrid grids. The computations arc made at Math numbvrs of 0.7 and 2.0. Full N-S equations arc discretized into finite volume form and solved by an algorithm in LU-SGS. The comparisons between computation and experimental data are made, and the detailed flow structure near grid fin is shown and examined.

关键词： computational fluid dynamics steady flow navier-stokes equation hybrid structureunstructured grid finite volume grid fin missile

Generation of linear and nonlinear waves in numerical wave tank using clustering technique-volume of fluid method

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Applied Mathematics and Mechanics(English Edition) 2012年第9期33卷 1179-1190页

作者： H.SAGHI M.J.KETABDARI S.BOOSHI Department of Civil Engineering Ferdowsi UniversityMashhad 91779-4897Iran Faculty of Marine Technology Amirkabir University of TechnologyTehran 15875-4413Iran

A two-dimensional （2D） numerical model is developed for the wave sim- ulation and propagation in a wave flume. The fluid flow is assumed to be viscous and incompressible, and the navier-stokes and continuity equations are used as the governing equations. The standard k-e model is used to model the turbulent flow. The navier- stokes equations are discretized using the staggered grid finite difference method and solved by the simplified marker and cell （SMAC） method. Waves are generated and propagated using a piston type wave maker. An open boundary condition is used at the end of the numerical flume. Some standard tests, such as the lid-driven cavity, the constant unidirectional velocity field, the shearing flow, and the dam-break on the dry bed, are performed to valid the model. To demonstrate the capability and accuracy of the present method, the results of generated waves are compared with available wave theories. Finally, the clustering technique （CT） is used for the mesh generation, and the best condition is suggested.

关键词： numerical wave tank free surface simulation navier-stokes equation stag-gered grid clustering technique (CT) wave generation

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

Mathematical modeling and parametric investigation of blood flow through a stenosis artery

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Applied Mathematics and Mechanics(English Edition) 2021年第11期42卷 1675-1684页

作者： A.ALI M.HUSSAIN M.S.ANWAR M.INC department of mathematics government college universityfaisalabad 38000pakistan department of natural sciences and humanities university of engineering and technologylahore 54890pakistan department of mathematics university of jhangistanbul 34295turkey department of computer engineering biruni universityIstanbul 34295Turkey department of mathematics firat universityelazig 23119turkey

In this study,a mathematical model is formulated to examine the blood flow through a cylindrical stenosed blood *** stenosis disease is caused because of the abnormal narrowing of flow in the *** narrowing causes serious health issues like heart attack and may decrease blood flow in the blood *** modeling helps us analyze such issues.A mathematical model is considered in this study to explore the blood flow in a stenosis artery and is solved numerically with the finite difference *** artery is an elastic cylindrical tube containing blood defined as a viscoelastic fluid.A complete parametric analysis has been done for the flow velocity to clarify the applicability of the defined ***,the flow characteristics such as the impedance,the wall shear stress in the stenotic region,the shear stresses in the throat of the stenosis and at the critical stenosis height are *** obtained results show that the intensity of the stenosis occurs mostly at the highest narrowing areas compared with all other areas of the vessel,which has a direct impact on the wall shear *** is also observed that the resistive impedance and wall shear pressure get the maximum values at the critical height of the stenosis.

关键词： stenotic artery blood flow finite difference method navier-stokes equation

A constrained particle dynamics for continuum-particle hybrid method in micro- and nano-fluidics

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Acta Mechanica Sinica 2006年第6期22卷 503-508页

作者： Jia Cui Guo Wei He Dewei Qi LNM Institute of Mechanics Chinese Academy of SciencesBeijing 100080 China Department of Paper and Chemical Engineering Western Michigan University Kalamazoo MI 49008 USA

A hybrid method of continuum and particle dynamics is developed for micro- and nano-fluidics, where fluids are described by a molecular dynamics （MD） in one domain and by the navier-stokes （NS） equations in another domain. In order to ensure the continuity of momentum flux, the continuum and molecular dynamics in the overlap domain are coupled through a constrained particle dynamics. The constrained particle dynamics is constructed with a virtual damping force and a virtual added mass force. The sudden-start Couette flows with either non-slip or slip boundary condition are used to test the hybrid method. It is shown that the results obtained are quantitatively in agreement with the analytical solutions under the non-slip boundary conditions and the full MD simulations under the slip bound- ary conditions.

关键词： Hybrid method Molecular dynamicsimulation navier-stokes equation Microfluidics

NUMERICAL WAVE FLUME WITH IMPROVED SMOOTHED PARTICLE HYDRODYNAMICS

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Journal of Hydrodynamics 2010年第6期22卷 773-781页

作者： ZHENG Jin-hai SOE Mee Mee ZHANG Chi HSU Tai-Wen State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Nanjing210098 China Department of Hydraulic and Ocean Engineering National Cheng Kung University Tainan 701 China

This paper presents an improved Nearest Neighboring Particle Searching （NNPS） technique for numerical modeling of water waves with the Smoothed Particle Hydrodynamics （SPH） method. The proposed technique differs from others by introducing the concept of Inner and Outer Particle Searching （lOPS） and shifting most of advanced CPU operations into simple addition operations. The IOPS method is shown to significantly improve the computational efficiency and reduce the CPU time especially for large number of particles, based on comparisons with other two NNPS methods. This method is implemented in a 2DV numerical wave flume conducted by the SPH method. Three test cases are examined, including generations and propagations of dam-breaking induced waves, solitary wave and irregular wave. Calculated results are in good agreements with experimental data and theoretical solutions with fairly satisfactory CPU time-consuming. The wave motions observed in physical facilities are successfully reproduced by the SPH numerical wave flume, revealing its robust capability of modeling realistic wave propagation and substantial potential for a wide variety of hydrodynamic problems.

关键词： particle searching technique Smoothed Particle Hydrodynamics (SPH) numerical wave flume navier-stokes equation

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