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Cylinder Surface (cylinder + surface)
Selected AbstractsStudy on the action of the active earth pressure by variational limit equilibrium methodINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 10 2010Li Xinggao Abstract Within the framework of limiting equilibrium approach, the problem of active earth pressure on rigid retaining wall is formulated in terms of the calculus of variations by means of Lagrange multipliers. It is transcribed as the functional of extreme-value problem by two undetermined function arguments, and is further transformed into determining the minimax solution of restrained functions incorporating the geometrical relations of the problem. The function of (fmincon) in the optimization toolbox of MATLAB 6.1 can be used to find the minimax solution. Computation results show there exist two kinds of modes of failure sliding along plane surface and rotating around log-spiral cylinder surface when the soil behind the walls reaches the critical active state. The magnitude of active earth pressure in the case of translational mode is less than that in the case of rotational mode. The location of action point of earth pressure in the case of translational mode is at or below height of the wall, and in the case of rotational mode, is above height of the wall. Preliminary study indicates a pair of numbers by two theoretical modes can be regarded as an interval estimation of active pressure. Copyright © 2009 John Wiley & Sons, Ltd. [source] Method of fundamental solutions for partial-slip fibrous filtration flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2009Shunliu Zhao Abstract In this study a Stokeslet-based method of fundamental solutions (MFS) for two-dimensional low Reynolds number partial-slip flows has been developed. First, the flow past an infinitely long cylinder is selected as a benchmark. The numerical accuracy is investigated in terms of the location and the number of the Stokeslets. The benchmark study shows that the numerical accuracy increases when the Stokeslets are submerged deeper beneath the cylinder surface, as long as the formed linear system remains numerically solvable. The maximum submergence depth increases with the decrease in the number of Stokeslets. As a result, the numerical accuracy does not deteriorate with the dramatic decrease in the number of Stokeslets. A relatively small number of Stokeslets with a substantial submergence depth is thus chosen for modeling fibrous filtration flows. The developed methodology is further examined by application to Taylor,Couette flows. A good agreement between the numerical and analytical results is observed for no-slip and partial-slip boundary conditions. Next, the flow about a representative set of infinitely long cylindrical fibers confined between two planar walls is considered to represent the fibrous filter flow. The obtained flowfield and pressure drop agree very well with the experimental data for this setup of fibers. The developed MFS with submerged Stokeslets is then applied to partial-slip flows about fibers to investigate the slip effect at fiber,fluid interface on the pressure drop. The numerical results compare qualitatively with the analytical solution available for the limit case of infinite number of fibers. Copyright © 2008 John Wiley & Sons, Ltd. [source] Numerical simulations of viscous flows using a meshless methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2008Changfu You Abstract This paper uses the element-free Galerkin (EFG) method to simulate 2D, viscous, incompressible flows. The control equations are discretized with the standard Galerkin method in space and a fractional step finite element scheme in time. Regular background cells are used for the quadrature. Several classical fluid mechanics problems were analyzed including flow in a pipe, flow past a step and flow in a driven cavity. The flow field computed with the EFG method compared well with those calculated using the finite element method (FEM) and finite difference method. The simulations show that although EFG is more expensive computationally than FEM, it is capable of dealing with cases where the nodes are poorly distributed or even overlap with each other; hence, it may be used to resolve remeshing problems in direct numerical simulations. Flows around a cylinder for different Reynolds numbers are also simulated to study the flow patterns for various conditions and the drag and lift forces exerted by the fluid on the cylinder. These forces are calculated by integrating the pressure and shear forces over the cylinder surface. The results show how the drag and lift forces oscillate for high Reynolds numbers. The calculated Strouhal number agrees well with previous results. Copyright © 2008 John Wiley & Sons, Ltd. [source] Theoretical and experimental study of vapor deposition onto a dressed body partAICHE JOURNAL, Issue 4 2008Paul Brasser Abstract When air-permeable clothing is worn, vapor will penetrate to the inside of the clothing. The vapor can deposit onto the skin, thus, forming a potential health threat. In a previous article a model was presented, which describes the airflow around body parts, covered with clothing. This airflow profile is used to calculate the vapor deposition onto the skin. A test setup was developed to validate the deposition model. Cylinders are used as a representative for human body parts. They are covered by a layer of protective clothing and exposed to vapor of methylsalicylate. The amount of vapor which deposites onto the surface of the cylinder is determined by using charcoal cloth. The influence of the clothing air permeability, the wind speed, the diameter of the cylinder, and the distance between clothing and cylinder surface was investigated. The experimental results show reasonable to good agreement with the model. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Surface anisotropy for monitoring the wear of IC engine cylindersLUBRICATION SCIENCE, Issue 1 2004C. Pandazaras Abstract The present work proposes a methodology for monitoring the wear of internal combustion engine cylinders. This could be useful in calculating the time at which maintenance should be done on such a tribosystem or in determining its lifetime. On the basis of experimental data obtained using a friction,wear simulator, and through the determination of certain standardised and non-standardised micro-geometric parameters of the cylinder surface that change with respect to operating time, it is shown that the characteristic that exhibits the most variation is the cylinder surface anisotropy. This factor participates to a large degree in the partial hydrodynamic lubrication mechanism of the reciprocating piston ring system and, as it is associated with the stage of wear, better expresses the characteristics of the cylinder's worn surface. As a consequence, by prescribing a limit for the maximum acceptable anisotropy as a basic criterion, the ultimate tolerable stage of wear is controlled simultaneously and vice versa. [source] Magnetohydrodynamic mixer of an electrolyte solutionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2004Svetlana Gorobets Abstract Mixing process was investigated as a function of metal element size, external magnetic field magnitude and distance from metal cylinder surface. Investigation results have shown an application of magnetic field is possible instrument for electrolyte flow parameter change. Magnetohydrodynamic mixer of an electrolytes solution was proposed on investigation results base. The advantages of proposed device are simple construction and absence energy consumption. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effects of Viscous Dissipation on Heat Transfer between an Array of Long Circular Cylinders and Power Law FluidsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2007R. P. Chhabra Abstract The free surface model has been combined with the equations of motion and of thermal energy to investigate the role of viscous dissipation on heat transfer between banks of long cylinders and power law (shear-thinning and shear-thickening) fluids. The equations of motion cast in the stream function/vorticity formulation have been solved numerically using a second-order accurate finite difference method to obtain extensive information on the behaviour of local and surface-averaged Nusselt numbers over a range of Reynolds numbers 1 , 500, for a wide range of power law indices (0.4 , n , 2.0), Brinkman numbers (0 , Br , 5) and Prandtl numbers (Pr = 1, 1000) at two representative solid volume fractions corresponding to the porosities of e = 0.4 and 0.9. Two different thermal boundary conditions are considered at the cylinder surface: constant temperature (CT) and constant heat flux (CHF). The results presented herein provide a fundamental knowledge about the influence of viscous dissipation on the heat transfer characteristics. The results reported herein further show that the effect of Brinkman number on heat transfer is strongly conditioned by the thermal boundary condition, Prandtl number and the power law index. On a combiné le modèle de surface libre aux équations de mouvement et de transfert de chaleur afin d'étudier le rôle de la dissipation visqueuse sur le transfert de chaleur entre des rangées de cylindres longs pour des fluides de loi de puissance (rhéofluidifiants et rhéoépaississants). Les équations de mouvement formulées en fonction de courant/vorticité ont été résolues numériquement à l'aide d'une méthode de différences finies du second ordre, afin d'obtenir des informations détaillées sur le comportement des nombres de Nusselt locaux et moyennés en surface pour une gamme de nombres de Reynolds compris entre 1 et 500, une large gamme d'indices de loi de puissance (0,4 , n , 2,0), de nombres de Brinkman (0 , Br , 5) et de nombres de Prandtl (Pr = 1,1000) à deux fractions de volume de solides correspondant à une porosité de e = 0,4 et 0,9. Deux conditions aux limites thermiques ont été considérées à la surface du cylindre: la température constante (CT) et le flux de chaleur constant (CHF). Les résultats présentés permettent de rendre compte de l'influence de la dissipation visqueuse sur les caractéristiques du transfert de chaleur et l'effet du nombre de Brinkman sur le transfert de chaleur qui est fortement influencé par la condition aux limites thermique, le nombre de Prandtl et l'indice de loi de puissance. [source] Structure of cyclized green fluorescent proteinACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2002Andreas Hofmann Crystals of cyclic green fluorescent protein (cGFP) engineered by the previously reported split intein technology [Iwai et al. (2001), J. Biol. Chem.276, 16548,16554] were obtained and the structure was solved using molecular replacement. Although the core of the protein can unambiguously be fitted from the first to the last residue of the genuine sequence, the electron density in the region of the linker peptide is rather poor owing to the high water content of the crystals. Therefore, it is concluded that this part of the protein is highly disordered in the present structure and is very flexible. This is supported by the absence of crystal contacts in the linker-peptide region and the fact that the core of the protein exhibits a very similar conformation to that known from other GFP structures, thereby not implicating any constraints arising from the presence of the artificial linker. Nevertheless, the density is consistent with the loop being intact, as confirmed by mass spectroscopy of dissolved crystals. The present structure contains an antiparallel cGFP dimer where the dimer interface is clearly different from other crystal structures featuring two GFP molecules. This adds further support to the fact that the cylinder surface of GFP is rather versatile and can employ various polar and non-polar patches in protein,protein interactions. [source] Assessment and Statistics of Surgically Induced AstigmatismACTA OPHTHALMOLOGICA, Issue thesis1 2008Kristian Næser Abstract. The aim of the thesis was to develop methods for assessment of surgically induced astigmatism (SIA) in individual eyes, and in groups of eyes. The thesis is based on 12 peer-reviewed publications, published over a period of 16 years. In these publications older and contemporary literature was reviewed1. A new method (the polar system) for analysis of SIA was developed. Multivariate statistical analysis of refractive data was described2,4. Clinical validation studies were performed. The description of a cylinder surface with polar values and differential geometry was compared. The main results were: refractive data in the form of sphere, cylinder and axis may define an individual patient or data set, but are unsuited for mathematical and statistical analyses1. The polar value system converts net astigmatisms to orthonormal components in dioptric space. A polar value is the difference in meridional power between two orthogonal meridians5,6. Any pair of polar values, separated by an arch of 45 degrees, characterizes a net astigmatism completely7. The two polar values represent the net curvital and net torsional power over the chosen meridian8. The spherical component is described by the spherical equivalent power. Several clinical studies demonstrated the efficiency of multivariate statistical analysis of refractive data4,9,11. Polar values and formal differential geometry describe astigmatic surfaces with similar concepts and mathematical functions8. Other contemporary methods, such as Long's power matrix, Holladay's and Alpins' methods, Zernike12 and Fourier analyses8, are correlated to the polar value system. In conclusion, analysis of SIA should be performed with polar values or other contemporary component systems. [source] Numerical simulation of heat transfer and fluid flow over two rotating circular cylinders at low Reynolds numberHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2010Nikolay Pavlovich Moshkin Abstract This paper presents a numerical investigation of the characteristics of two-dimensional heat transfer in a steady laminar flow around two rotating circular cylinders in a side-by-side arrangement. The simulation is validated by comparing our computational results for the large gap-spacing between cylinder surfaces with the available numerical and experimental data for a single cylinder. Numerical simulations were carried out for the Reynolds number range 10,Re ,40, for the Prandtl number range 0.7,Pr ,50, and for a variety of absolute rotational speeds (|,|,2.5) at different gap spacings. The study revealed that for the range of parameters considered the rate of heat transfer decreases with the increasing speed of rotation. An increase of the Prandtl number resulted in an increase in the average Nusselt number. The streamlines and isotherms are plotted for a numbers of cases to show the details of the velocity and thermal fields. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20293 [source] | |||||||||||||||||||||||||