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[en] This book introduces basic conception and definition of fluid dynamics, stress and strain rate, hydrostatics like Euler's movement equation, standard atmosphere, pressure measurement, and buoyancy, fluid kinematics such as acceleration, and relationship between Storkes flow function and velocity potential, integral representation of basic law by examiner, differential analysis of flow behavior, dimensional analysis and analogy like determination of dimensionless number, dimensionless number related fluid flow, non-dimensionalization of basic equation and viscous flow.
[en] This book deals with inviscid flow, which includes summary, potential flow, two dimension potential flow such as basic flow combination of two dimension potential flow thin airfoil theory and vortex street, axial symmetry three dimension potential flow like three dimension doublet, and semi-infinite body of revolution. It also explains viscous flow of peripheral incompressible fluid with boundary layer theory and fluid around materials which are in a fluid, compressive flow like basic thermodynamic relationship, normal one dimension compressive flow, expansion wave, compressive flow in nozzle, diffuser and wind tunnel and open channel flow.
[en] This paper presents a numerical scheme for fluid-structure interaction, especially for flexible structures. The lattice Boltzmann method with an immersed boundary technique using a direct forcing scheme is used for the fluid , and a finite element method with Euler beam elements is used for the flexible plate. The direct forcing scheme of the lattice Boltzmann method was improved for the immersed boundary scheme by introducing the occupation ratio of fluid lattices among the interpolated lattices. We compared the results of our proposed scheme with the known results of conventional schemes. Using the proposed numerical scheme, the flow around the flexible plate in a free stream is simulated for the effect of flexibility. Our results show that the major role of the flexibility of the flexible plate is the reduction of the resistance from flow. From the unsteady flow around a flexible plate, we found that the St of the flexible plate up to Re < 80 increased regardless of plate flexibility, but the St in the range of Re > 120 was dependent on plate flexibility. In the range of Re > 120 , the St of very flexible plate increased with increasing Re, while the St of rigid plate decreased with increasing Re
[en] In this paper, the unsteady behavior of the viscous flow field past an impulsively started elliptic cylinder is studied numerically. In order to analyze flow field, we introduce vortex particle method. The vorticity transport equation is solved by fractional step algorithm which splits into convection term and diffusion term. The convection term is calculated with Biot-Savart law, the no-through boundary condition is employed on solid boundaries. The diffusion term is modified based on the scheme of particle strength exchange. The particle redistributed scheme for general geometry is adapted. The flows around an elliptic cylinder are investigated for various attack angles at Reynolds number 200. The comparison between numerical results of present study and experimental data shows good agreements
[en] Astrophysics, fluid dynamics, molecular dynamics or many other physical problems can be considered as a system composed of many particles, so called N-body system. Because these simulations are prohibitively expensive for large N, the fast algorithms and the parallel schemes must be employed. In this study, the performance effects of three domain decomposition schemes(Orthogonal Recursive Bisection, Morton order, Peano-Hilbert Order) and the locally essential tree are examined. We simulated a spherical vortex sheet problem and a flow past a sphere at Re=100 using the vortex element method with the 128-node linux cluster. The performance difference was found according to different particle distributions. In the case of computational domain with large aspect ratio, the orthogonal recursive bisection shows more efficient than others. However, using the locally essential tree, the performance differences between domain decomposition schemes are decreased
[en] The nanochannels are characterized by a large surface-to-volume ratio, so that the surface properties strongly affect the flow resistance. We present here the results showing that the effect of wetting properties and the surface roughness may considerably reduce the friction of fluid past the boundaries. For a simple fluid flowing over hydrophilic and hydrophobic surfaces, the influences of surface roughness are investigated by the NonEquilibrium Molecular Dynamics (NEMD) simulations. The solid surfaces with embossed squares were considered as the rough surface. It was found that the fluid slip at near a solid surface highly depends on the wall-fluid interaction and the surface roughness. For the fluids over hydrophobic surfaces, the snapshots of fluid molecules show that an air gap or nanobubble exists at the fluid-solid interface. Due to the increase of drag resistance at the solid-fluid interface, the fluid slip on rough surfaces is smaller than that on smooth surface walls
[en] Optimization of a heat exchanger with internally finned circular tubes has been performed for three-dimensional periodically fully developed turbulent flow and heat transfer. The design variables of fin number N, fin width (d1,d2) and fin height(H) , are numerically optimized for the limiting conditions of N = 22∼37, d1= 0.5∼1.5 mm, d2 0.5∼1.5 mm, H = 0.1∼1.5. Due to the periodic boundary conditions along main flow direction, the three layers of meshes are considered. The CFD and the mathematical optimization are coupled to optimize the heat exchanger. The flow and thermal fields are predicted using the finite volume method and the optimization is carried out by using the Sequential Quadratic Programming (SQP) method which is widely used in the constrained nonlinear optimization problem
[en] The mechanistic aspects of electrochemical reductions of UVIO2(acac)2dmso(acac=acetylacetonate, dmso=dimethyl sulfoxide) complex with bidentate ligand(acac) in DMSO were investigated by using cyclic voltammetry, normal pulse voltammetry, and spectrophotometer equipped with an optical transparent thin layer electrode cell. It is concluded that the uranyl complexes with bidentate ligands at the equatorial plane form stable U(V) complexes by the electrochemical reduction and that their molar extinction coefficients in the visible region are very small. (J.P.N.)
[en] The shape optimization of an airfoil has been performed for an incompressible viscous flow. In this study, Pareto frontier sets, which are global and non-dominated solutions, can be obtained without various weighting factors by using the multi-objective genetic algorithm. An NACA0012 airfoil is considered as a baseline model, and the profile of the airfoil is parameterized and rebuilt with four Bezier curves. Two curves, from leading to maximum thickness, are composed of five control points and the rest, from maximum thickness to tailing edge, are composed of four control points. There are eighteen design variables and two objective functions such as the lift and drag coefficients. A generation is made up of forty-five individuals. After fifteenth evolutions, the Pareto individuals of twenty can be achieved. One Pareto, which is the best of the reduction of the drag force, improves its drag to 13% and lift-drag ratio to 2%. Another Pareto, however, which is focused on increasing the lift force, can improve its lift force to 61%, while sustaining its drag force, compared to those of the baseline model
[en] The Probabilistic Safety Assessment (PSA) model enables to find the relative priority of accident scenarios, weak points in achieving accident prevention or mitigation, and insights to improve those vulnerabilities. Thus, PSA consider realistic calculation for precise and confidence results. However, PSA model still 'conservative' aspects in the procedures of developing a PSA model. One of the sources for the conservatism is caused by the assumption of safety analysis and the estimation of failure frequency. Recently, Surveillance, Diagnosis, and Prognosis (SDP) is a growing trend in applying space and aviation systems in particular. Furthermore, a study dealing with the applicable areas and state-of-the-art status of the SDP in nuclear industry was published. SDP utilizing massive database and information technology among such enabling techniques is worthwhile to be highlighted in terms of the capability of alleviating the conservatism in the conventional PSA. This paper review the concept of integrating PSA and SDP and suggest the updated methodology of Initiating Event (IE) using prognostics. For more detailed, we focus on IE of the Steam Generator Tube Rupture (SGTR) considering tube degradation. This paper is additional research of previous our suggested the research. In this paper, the concept of integrating PSA and SDP are suggested. Prognostics algorithms in SDP are applied at IE, Bes in the Level 1 PSA. As an example, updating SGTR IE and its ageing were considered. Tube ageing were analyzed by using PASTA and Monte Carlo method. After analyzing the tube ageing, conventional SGTR IE were updated by using Bayesian approach. The studied method can help to cover the static and conservatism in PSA