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Numerical simulations of viscous flow around the obliquely towed KVLCC2M model in deep and shallow water

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Journal of Hydrodynamics 2016年第3期28卷 506-518页

作者：孟庆杰万德成 State Key Laboratory of Ocean Engineering School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong University Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration

By solving the unsteady Reynolds averaged Navier-Stokes （RANS） equations in combination with the k- ε SST turbulence model, the unsteady viscous flow around the obliquely towed tanker KVLCC2M model in both deep and shallow waters is simulated and the hydrodynamic forces, the surface pressure distribution, and the wake field are calculated. The overset grid technology is used to avoid the grid distortion in large drift angle cases. The effects of the free surface are taken into account. At the first stage, the deep water cases with five oblique angles are designed as the benchmark test cases. The predicted wake field, the surface pressure distribution and the hydrodynamic forces acting on the hull agree well with the corresponding experimental data, implying the capability of the present method in the prediction of the viscous flow around the tanker drifting in shallow water. A set of systematic computations with varying water depths and drift angles are then carried out to study the viscous flow around the model drifting in shallow water. The forces and moments, as well as the surface pressure distribution are predicted and analyzed. The most significant changes such as the increased stagnation pressure in the bow, the acceleration of the flow along the ship＇s sides and in the gap between ship and seabed, the lower hull pressure and finally, the stronger vortices along the bilges and weaker vortices with larger diameters in the wake are noticed.

关键词： drift motionm shallow water viscous flow hydrodynamic forces manoeuvability

Grain boundary diffusion and viscous flow governed mechanical relaxation in polycrystalline materials

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Science China Materials 2022年第5期65卷 1403-1412页

作者： Chuangchuang Duan Yujie Wei State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Sciences University of Chinese Academy of SciencesBeijing 100049China

Grain boundary(GB) diffusion and viscous flow play dominant roles in mechanical relaxation of polycrystalline materials. The pioneering work of Zener and Kê, by accounting for relaxation in GBs by viscous shearing, predicts a single peak in the internal friction spectrum. Later investigations show the existence of two to three peaks in the internal friction spectrum when taking into account both GB diffusion and viscous flow for dissipation. In this paper, we further identify the characteristic relaxation modes in polycrystalline materials. We illustrate that competitive viscous flow and diffusion for normal stress relaxation give rise to distinct dependence of relaxation time on grain size. We construct an internal friction spectrum mapping based on the competitive deformation mechanisms including viscous flow in both normal and tangential directions and GB diffusion. The essential features of internal friction spectrum of polycrystalline materials from our analysis are consistent with available experimental observations. These findings may also be applicable to study relaxation dynamics of other material systems such as metallic glasses and porous materials.

关键词： grain boundary diffusion viscous flow internal friction spectrum polycrystalline materials Zener-Kêdissipation

Kutta-Joukowski force expression for viscous flow

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Science China(Physics,Mechanics & Astronomy) 2015年第2期58卷 90-94页

作者： LI Juan XU YiZhe WU ZiNiu Department of Engineering Mechanics Tsinghua University

The Kutta Joukowski(KJ) theorem, relating the lift of an airfoil to circulation, was widely accepted for predicting the lift of viscous high Reynolds number flow without separation. However, this theorem was only proved for inviscid flow and it is thus of academic importance to see whether there is a viscous equivalent of this theorem. For lower Reynolds number flow around objects of small size, it is difficult to measure the lift force directly and it is thus convenient to measure the velocity flow field solely and then, if possible, relate the lift to the circulation in a similar way as for the inviscid KJ theorem. The purpose of this paper is to discuss the relevant conditions under which a viscous equivalent of the KJ theorem exists that reduces to the inviscid KJ theorem for high Reynolds number viscous flow and remains correct for low Reynolds number steady flow. It has been shown that if the lift is expressed as a linear function of the circulation as in the classical KJ theorem, then the freestream velocity must be corrected by a component called mean deficit velocity resulting from the wake. This correction is small only when the Reynolds number is relatively large. Moreover, the circulation, defined along a loop containing the boundary layer and a part of the wake, is generally smaller than that based on inviscid flow assumption. For unsteady viscous flow, there is an inevitable additional correction due to unsteadiness.

关键词： lift force Kutta Joukowski expression viscous flow

AN　INTEGRATEDC　METHOD　FOR　COMPUTING　COMPUTING　THE　INTERNAL　AND　EXTERNAL　viscous　flow　FIELD　AROUND　THE　DUCTED　PROPULSOR　BEHIND　AN　AXISYMMETRIC　BODY

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Journal of Hydrodynamics 1995年第3期7卷 72-83页

作者： Zhou Lian-di Zhao Feng(China Ship Scientific Research Center, P.O. Box 116, Wuxi 214082, P. R. China) China Ship Scientific Research Cent Wuxi China

This paper presents an effective method for computing the internal and external viscous flow field around the ducted propulsor behind an axisymmetric they by using a new Navier-Stokes equations solver with primitive variable continuity equation formulation. In the present numerical method, the calculation equation for pressure with well-defined coefficient,which form is similar to the artificial compressibility method, is developed. A semi-staggered grid system is adopted. Not only the advantage of staggered grid system can be retained but the boundary conditions on the inner and outer surface of the duct can be also carried out easily. By using a special grid system and the programming technique for implementing the jump boundary condition on the duct surfaces, the internal and external viscous flow field around the ducted propulsor behind the axisymmetric they may be calculated integrally in an unified numbered grid system. Some configurations are calculated and compared with experimental date and numerical results of other methods. Illustrative calculations are also presented for a stern of axisymmetric body with the backstep fitted a duct to illustrate the capability of the present method. Beside that, the effect of axial distribution of they force is considered and discussed in order to extend the application range of the present method.

关键词： ducted propulsor viscous flow semi-staggered grid

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Applied Mathematics and Mechanics(English Edition) 2012年第7期33卷 923-930页

作者： M. A. A. HAMAD M. FERDOWS Department of Mathematics Faculty of Science Assiut University School of Mathematical Sciences Universiti Sains Malaysia Department of Mathematics University of Dhaka

The boundary-layer flow and heat transfer in a viscous fluid containing metallic nanoparticles over a nonlinear stretching sheet are analyzed. The stretching velocity is assumed to vary as a power function of the distance from the origin. The governing partial differential equation and auxiliary conditions are reduced to coupled nonlinear ordinary differential equations with the appropriate corresponding auxiliary conditions. The resulting nonlinear ordinary differential equations （ODEs） are solved numerically. The effects of various relevant parameters, namely, the Eckert number Ec, the solid volume fraction of the nanoparticles ~, and the nonlinear stretching parameter n are discussed. The comparison with published results is also presented. Different types of nanoparticles are studied. It is shown that the behavior of the fluid flow changes with the change of the nanoparticles type.

关键词： nanofluid nonlinearly stretching sheet similarity solution nonlinearordinary equation partial differential equation viscous flow

BLOCK ITERATIVE METHODS FOR LINEAR ALGEBRAIC EQUATION AND DOMAIN DECOMPOSITION METHOD FOR INCOMPRESSIBLE viscous flow

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Journal of Hydrodynamics 2002年第4期14卷 73-80页

作者： Ren, An-Lu Zou, Jian-Feng Zhou, Yong-Xia Li, Guang-Wang Dept. of Mech. Zhejiang Univ. Hangzhou 310027 China

It was proved numerically that the Domain Decomposition Method CDDM) with one layer overlapping grids is identical to the block iterative method of linear algebra equations. The results obtained by using DDM could be in reasonable agreement with the results of full-domain simulation. With the three dimensional solver developed by the authors, the flow field in a pipe was simulated by using the full-domain DDM with one layer overlapping grids and with patched grids respectively. Both of the two cases led to the convergent solution. Further research shows the superiority of the DDM with one layer overlapping grids to the DDM with patched grids. A comparison between the numerical results obtained by the authors and the experimental results given by Enayet[3] shows that the numerical results are reasonable.

关键词： Computational fluid dynamics Computer simulation Iterative methods Linear equations viscous flow

Numerical Simulation of viscous flow over a Grooved Surface by the Lattice Boltzmann Method

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Journal of Shanghai Jiaotong university(Science) 2016年第2期21卷 143-150页

作者：黄桥高潘光 School of Marine Science and Technology Northwestern Polytechnical University

The motivation of this work is to investigate a grooved surface's drag reduction. The viscous flow through a two-dimensional microchannel with the grooved surface is analyzed by the lattice Boltzmann method(LBM). The effects of the grooved surface on the streamline patterns, the velocity distributions near wall region and the fluid shear stress distributions on the walls at different Reynolds numbers are studied. In addition, the influences of the groove's geometrical parameters on the grooved surface's drag reduction are discussed. The numerical results confirm the grooved surface's drag reduction and present the drag reduction law of the grooved surface.

关键词： grooved surface drag reduction viscous flow lattice Boltzmann method(LBM) momentum-exchange method

Numerical Simulation of viscous flow Around a Rolling Cylinder with Ship-Like Section

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China Ocean Engineering 1995年第1期10卷 9-18页

作者： Chung, Huaixin Miao, Guoping Liu, Yingzhong

Two-dimensional unsteady incompressible viscous flow around a rolling cylinder with ship-like section is numerically simulated by employing the computational scheme previously developed by the authors, in which the continuity and momentum equations are satisfied simultaneously at each time step for oscillating flow. The numerical results show that the motion of vortices around a rolling ship hull is cyclical. It is found that the location of the vortices is very similar to the existing experimental result. Using these simulation results, we can calculate the roll damping of ships including viscous effects.

关键词： viscous flow numerical simulation two-dimensional cylinder rolling motion

A CFD Based Investigation of the Unsteady Hydrodynamic Coefficients of 3-D Fins in viscous flow

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Journal of Marine Science and Application 2010年第3期9卷 250-255页

作者： Nazir Zulfiqar 苏玉民王兆立 State Key Laboratory of Autonomous Underwater Vehicle Harbin Engineering University PN Dockyard West Wharf RoadKarachi 74000Pakistan

The motion of the fins and control surfaces of underwater vehicles in a fluid is an interesting and challenging research *** the effect of fin oscillations on the fluid flow around such a body is highly unsteady, generating vortices and requiring detailed analysis of fluid-structure *** understanding of the complexities of such flows is of interest to engineers developing vehicles capable of high dynamic performance in their propulsion and *** the present study, a CFD based RANS simulation of a 3-D fin body moving in a viscous fluid was *** investigated hydrodynamic performance by evaluating the hydrodynamic coefficients (lift, drag and moment) at two different oscillating frequencies.A parametric analysis of the factors that affect the hydrodynamic performance of the fin body was done, along with a comparison of results from *** results of the simulation were found in close agreement with experimental results and this validated the simulation as an effective tool for evaluation of the unsteady hydrodynamic coefficients of 3-D *** work can be further be used for analysis of the stability and maneuverability of fin actuated underwater vehicles.

关键词： oscillating 3-D fin RANS hydrodynamic performance viscous flow