Axial Symmetry

Measurements of the velocity and concentration in axisymmetric, turbulent, isothermal and buoyant jets have been performed with laser-Doppler velocimetry and planar and point laser-induced fluorescence to quantify the mixing enhancement achieved by periodic forcing when the jet exit has a fully-developed turbulent pipe flow, a situation less well-studied than the case of laminar initial conditions. It was found that forcing at Strouhal numbers around 0.6 enhances mixing in the developing region of the jet and this enhancement increased with increasing amplitude of excitation, consistent with results of initially-laminar jets. The initial turbulence intensity did not have any effect, but an increase in the initial lengthscale of the turbulence, controlled by a perforated plate inside the nozzle, caused faster mixing. In agreement with previous experiments, the initial conditions of the jet did not affect the far-field rate of decay, but the jet-fluid concentration there was significantly reduced by forcing due to the increased mixing during the early stages of development, an effect that can be described by a smaller virtual origin in decay laws of jet decay. These results are independent of the Froude number because the initial conditions have an influence only in the early stages where the flow is still momentum dominated.

Optimization of process parameters in sheet metal forming is an important task to reduce manufacturing cost. To determine the optimum values of the process parameters, it is essential to find their influence on the deformation behaviour of the sheet metal. The significance of three important process parameters namely, die radius, blank holder force and friction coefficient on the deep-drawing characteristics of a stainless steel axi-symmetric cup was determined. Finite element method combined with Taguchi technique form a refined predictive tool to determine the influence of forming process parameters. The Taguchi method was employed to identify the relative influence of each process parameter considered in this study. A reduced set of finite element simulations were carried out as per the Taguchi orthogonal array. Based on the predicted thickness distribution of the deep drawn circular cup and analysis of variance test, it is evident that die radius has the greatest influence on the deep drawing of stainless steel blank sheet followed by the blank holder force and the friction coefficient. Further, it is shown that a blank holder force application and local lubrication scheme improved the quality of the formed part.

Ultimate capacity of large diameter bored piles is usually determined from pile loading tests as recommended by several international codes and foundation design standards. However, loading of this type of piles till achieving apparent failure is practically seldom. In this paper, numerical analyses are carried out to simulate load test of a large diameter bored pile performed at the location of Alzey highway bridge project (Germany). Test results of pile load settlement relationship till failure as well as results of the base and shaft resistances are available. Apparent failure was indicated in this test by the significant increase of the induced settlement during the last load increment applied on the pile head. Measurements of this pile load test are used to assess the quality of the numerical models investigated. Three different material soil models are implemented in the analyses: Mohr coulomb (MC), Soft soil (SS), and Modified Mohr coulomb (MMC). Very good agreement is obtain...

Interactions between deformable composite structures and compressible multiphase flow are common for many marine/submarine problems. Recently, there has been an increased interest in the application of composite structures in the marine industry (e.g. propulsion system, ship hulls, marine platforms, marine turbines, etc) to take advantage their high stiffness to weight and strength to weight ratios, and high impact/shock resistance characteristics. It is therefore important to evaluate the performance of composite structures subject to dynamic loads. In this paper, a coupled Eulerian-Lagrangian numerical method is proposed to model the two-dimensional (2D) or axisymmetric response of deformable composite structures subject to shock and blast loads. The method couples an Eulerian compressible multiphase fluid solver with a general Lagrangian solid solver using an interface capturing method, and is validated using analytical, numerical, and experimental results. A 2D case study is shown for an underwater explosion beneath a three-layered composite structure with clamped ends. The importance of 2D fluid-structure interaction effects on the transient response between composite structures and compressible multiphase flow is discussed.

-Nousétudions l'écoulement dans le plan de sortie d'un jet tournantà grand nombre de Reynolds généréà l'aide d'un nid d'abeilles tournant suivi d'une tuyère convergente. Des mesures fil chaud réalisées en sortie de deux tuyères de taux de contraction différents montrent l'apparition progressive de turbulence pour des valeurs identiques du taux de rotation de l'écoulement en amont des tuyères. Afin d'expliquer ce phénomène, nousétudions donc la dynamique de l'écoulement de conduite compris entre le nid d'abeilles et le plan de sortie des convergents. Un modèle stationnaire simple d'écoulement est d'abord introduit. Il montre la possibilité d'une recirculationà la paroi de la tuyère lorsque les conditions amont sont proches de la criticité, définie au sens des ondes inertielles pouvant se propager dans l'écoulement. Nous trouvons ensuite que ces solutions sont globalement stablesà des perturbations axisymétriques, mais sont susceptibles d'amplifier fortement des perturbations de petiteéchelle initiéesà l'amont de l'écoulement et suivies le long de leur trajectoire jusqu'en sortie.

Microstructure and material flow of aluminum alloys have a significant influence on the mechanical properties and surface quality. In extrusion of aluminum billets at high temperatures the microstructure is dependent on the alloy and the forming and temperature history. A prediction of grain size and precipitation is of increasing importance in order to design the process by adjustment of parameters such as punch speed, temperatures, and quenching. To give references for microstructure prediction based on material flow, and with it strain and strain rate history, this paper deals with the microstructure during the extrusion process of AA6060, AA6082, and AA7075 alloys. Billets have been partly extruded to axisymmetric round profiles and the microstructure of the press rests consisting of the billet rests in container and die has been considered. Furthermore, these rests have been analyzed to show the material flow, dynamic and static recrystallization based on macro etchings and visible microstructure under different conditions, e.g. as in the area of high strain rate near the container wall, or in dead zones [I]. To allow an accurate simulation of the extrusion process, punch force and temperature conditions during the tests have been measured and are presented in this paper, too.

The self-excitation mechanism of the acoustic diametral modes of an axisymmetric internal cavity-duct system is studied for a Mach number range up to 0.4. The effect of cavity dimensions on the excitation mechanism is investigated experimentally and numerically. Experiments are conducted on three cavity depths and six cavity lengths for each depth. Numerical simulations of the mode shapes are also performed to determine the effect of cavity dimensions on the particle velocity field of the diametral modes. For all the tested configurations, the diametral modes are strongly excited at relatively low Mach numbers (as low as 0.1). The pulsation amplitude at resonance is found to increase as the cavity becomes shorter or deeper, relative to the main pipe diameter. The test results provide new insights into the excitation mechanism of diametral modes, the effect of the cavity length to depth ratio on the Strouhal numbers of acoustic resonances caused by various shear-layer modes of the cavity, and into the effect of the particle velocity field of the acoustic modes on the mode selectivity mechanism which determines the dominant acoustic mode during resonance. r (K. Aly). fluid-resonant mechanism in piping systems, in which the feedback effect is produced by the velocity fluctuations resulting from acoustic resonance. The feedback cycle of events in this mechanism starts when the unstable shear layer is triggered at the cavity leading edge by small vorticity perturbations. These perturbations grow rapidly as they are convected downstream by the mean flow. As these amplified vorticity perturbations reach the cavity downstream corner, part of the energy of the vortical structures is transferred into acoustic energy due to the interaction between the vorticity field and the acoustic field. When the phasing of these events is favourable, the generated acoustic energy amplifies or sustains the acoustic resonance mode of the cavity. The velocity fluctuation associated with the acoustic resonance then triggers the shear layer at the cavity leading edge, which closes the feedback cycle. It is clear from this cycle of events that the nature of the acoustic mode, including its spatial compatibility with the shear layer oscillation mode, has a strong effect on whether this feedback mechanism can be self-sustained or not.

This work considers the analysis of a cracked semi-infinite cylinder and a finite cylinder. Material of the cylinder is assumed to be linearly elastic and isotropic. One end of the cylinder is bonded to a fixed support while the other end is subjected to axial tension. Solution of this problem can be obtained by superposition of solutions for an infinite cylinder subjected to uniformly distributed tensile load at infinity (I) and an infinite cylinder having a penny-shaped rigid inclusion at z = 0 and two penny-shaped cracks at z = ±L (II). General expressions for the perturbation problem (II) are obtained by solving Navier equations with Fourier and Hankel transforms. When the radius of the inclusion approaches the radius of the cylinder, the end at z = 0 becomes fixed and when the radius of the cracks approach the radius of the cylinder, the ends at z = ±L become cut and subject to uniform tensile load. Formulation of the problem is reduced to a system of three singular integral equations. By using Gauss-Lobatto and Gauss-Jacobi integration formulas, these three singular integral equations are converted to a system of linear algebraic equations which is solved numerically.

Axisymmetric stagnation-point flow is considered. A Newtonian fluid impinges orthogonally on a plane surface lubricated by a thin non-Newtonian liquid film of variable thickness. A slip-flow boundary condition is deduced, which allows for partial slip at the surface. The amount of slip, from full slip to no-slip, is controlled by a dimensionless slip coefficient. Similarity solutions are generally prohibited by the slip-flow boundary condition, except for one particular value of the power-law index of the lubricant. Solutions are presented for this case in order to demonstrate the influence of partial slip on the stagnation point flow. With increasing slip and reduced surface stress, a thinning of the viscous boundary layer is observed. The classical Homann flow is recovered in the no-slip limit.

An exact three-dimensional analysis for steady-state dynamic response of an arbitrarily thick, isotropic, and functionally graded plate strip due to the action of a transverse distributed moving line load which is propagating parallel to the infinite simply supported edges of the plate at constant speed is presented based on the linear elasticity theory. The inhomogeneous plate is approximated by a laminate model, for which the solution is expected to gradually approach the exact one as the number of layers increases. The problem solution is derived by using Fourier transformation with respect to a moving reference frame in conjunction with the classical transfer matrix approach entailing the continuity of displacement and stress components at the interfaces of neighboring layers. The analytical results are illustrated with numerical examples in which a metal-ceramic (ZrO 2 -Al) FGM plate strip of unit width is subjected to a half-sine normal line load of constant amplitude traveling along the strip at uniform speeds. Four types of FGM plate strips are configured, and the effects of load velocity, material compositional gradient, and plate thickness on the basic dynamic field quantities are evaluated and discussed. Also, the response curves for the FGM plates are compared with those of equivalent bilaminate plates containing comparable total volume fractions of constituent materials. Limiting cases are considered and good agreements with the solutions available in the literature are obtained.

Although stuffing boxes are old systems used to ensure stem valve sealing, the analytical developments of the stresses and the displacements generated during assembly and operation are very limited and seldom verified and the studies carried out on these devices are either restricted or not accessible. Moreover, even with the evolution of calculation and simulation means, studies based on numerical

Plastic deformation of structures absorbs substantial kinetic energy when impact occurs. Therefore, energy-absorbing components have been extensively used in structural designs to intentionally absorb a large portion of crash energy. On the other hand, high peak crushing force, especially with regard to mean crushing force, may lead to a certain extent and indicate the risk of structural integrity. Thus, maximizing energy absorption and minimizing peak to mean force ratio by seeking for the optimal design of these components are of great significance. Along with this analysis, the collapse behavior of square, hexagonal, and octagonal cross-sections as the baseline for designing a newly introduced 12edge section for stable collapse with high energy absorption capacity was characterized. Inherent dissipation of the energy from severe deformations at the corners of a section under axial collapse formed the basis of this study, in which multi-cornered thin-walled sections was focused on. Sampling designs of the sections using design of experiments (DOE) based on Taguchi method along with CAE simulations was performed to evaluate the responses over a range of steels grades starting from low end mild steels to high end strength. The optimization process with the target of maximizing both specific energy absorption (SEA) and crush force efficiency (CFE), as the ratio of mean crushing load to peak load, was carried out by nonlinear finite element analysis through LS-DYNA. Based on single-objective and multi-objective optimizations, it was found that octagonal and 12-edge sections had the best crashworthiness performance in terms of maximum SEA and CFE.

In this paper, a free vibration analysis of moderately thick circular functionally graded (FG) plate integrated with two thin piezoelectric (PZT4) layers is presented based on Mindlin plate theory. The material properties of the FG core plate are assumed to be graded in the thickness direction, while the distribution of electric potential field along the thickness of piezoelectric layers is simulated by sinusoidal function. The differential equations of motion are solved analytically for two boundary conditions of the plate: clamped edge and simply supported edge. The analytical solution is validated by comparing the obtained resonant frequencies with those of an isotropic host plate. The emphasis is placed on investigating the effect of varying the gradient index of FG plate on the free vibration characteristics of the structure. Good agreement between the results of this paper and those of the finite element analyses validated the presented approach.

The non-linear response of empty and #uid-"lled circular cylindrical shells to harmonic excitations is investigated. Both modal and point excitations have been considered. The model is suitable to study simply supported shells with and without axial constraints. Donnell's non-linear shallow-shell theory is used. The boundary conditions on radial displacement and the continuity of circumferential displacement are exactly satis"ed. The radial de#ection of the shell is expanded by using a basis of seven linear modes. The e!ect of internal quiescent, incompressible and inviscid #uid is investigated. The equations of motion, obtained in Part I of this study, are studied by using a code based on the collocation method. The validation of the present model is obtained by comparison with other authoritative results. The e!ect of the number of axisymmetric modes used in the expansion on the response of the shell is investigated, clarifying questions open for a long time. The results show the occurrence of travelling wave response in the proximity of the resonance frequency, the fundamental role of the "rst and third axisymmetric modes in the expansion of the radial de#ection with one longitudinal half-wave, and limit cycle responses. Modes with two longitudinal half-waves are also investigated.

In this article, we investigate the response of a thin superconducting shell to an arbitrary external magnetic field. We identify the intensity of the applied field that forces the emergence of vortices in minimizers, the so-called first critical field H c1 in Ginzburg-Landau theory, for closed simply connected manifolds and arbitrary fields. In the case of a simply connected surface of revolution and vertical and constant field, we further determine the exact number of vortices in the sample as the intensity of the applied field is raised just above H c1 . Finally, we derive via Γ -convergence similar statements for three-dimensional domains of small thickness, where in this setting point vortices are replaced by vortex lines.

Microstructure and material flow of aluminum alloys have a significant influence on the mechanical properties and surface quality. In extrusion of aluminum billets at high temperatures the microstructure is dependent on the alloy and the forming and temperature history. A prediction of grain size and precipitation is of increasing importance in order to design the process by adjustment of parameters such as punch speed, temperatures, and quenching. To give references for microstructure prediction based on material flow, and with it strain and strain rate history, this paper deals with the microstructure during the extrusion process of AA6060, AA6082, and AA7075 alloys. Billets have been partly extruded to axisymmetric round profiles and the microstructure of the press rests consisting of the billet rests in container and die has been considered. Furthermore, these rests have been analyzed to show the material flow, dynamic and static recrystallization based on macro etchings and visible microstructure under different conditions, e.g. as in the area of high strain rate near the container wall, or in dead zones [I]. To allow an accurate simulation of the extrusion process, punch force and temperature conditions during the tests have been measured and are presented in this paper, too.

The article presents results of the numerical simulations carried out for the transport phenomena occurring during the Czochralski crystal growth process. Due to computational constraints, the simulations were kept limited to axisymmetric geometries. The simulation model gives special attention to the crystal-melt interface and oxygen transport, and treats the crystal-melt interface according to Stefan's balance, by explicitly moving the grids. Oxygen evaporation at the free surface is expressed by balancing the corresponding fluxes. Marangoni convection due to temperature gradients is also incorporated into the model. The role of an applied axial magnetic field in controlling fluid flow, interface shape, and oxygen levels is studied in detail. The effect of crystal and crucible rotations is also examined under the influence of the magnetic field. Simulation results show that the application of an axial magnetic field leads to flatter interfaces and lower oxygen concentration levels, but makes the oxygen distribution non-uniform at the crystal-melt interface.

In this work, we used a recently proposed constitutive model that addresses the elastic behavior of viscoplastic liquids. We used the equation in an expansion-contraction axisymmetric flow, and compared the results with experimental data found in the literature. Steady, inertialess numerical solutions were obtained by solving the balance equations of mass and momentum via the finite element method. We obtained the velocity and stress fields for different combinations of the governing parameters, and observed that elasticity leads to significant changes in the shape and position of the yield surface, affecting both the extra-stress and the rate of deformation fields in the cavity. The trends observed are in qualitative agreement with visualization results available in the literature.

In this Letter, we present analytical and numerical solutions for an axis-symmetric diffusion-wave equation. For problem formulation, the fractional time derivative is described in the sense of Riemann-Liouville. The analytical solution of the problem is determined by using the method of separation of variables. Eigenfunctions whose linear combination constitute the closed form of the solution are obtained. For numerical computation, the fractional derivative is approximated using the Grünwald-Letnikov scheme. Simulation results are given for different values of order of fractional derivative. We indicate the effectiveness of numerical scheme by comparing the numerical and the analytical results for α = 1 which represents the order of derivative.

Toroidal shells are widely used in structural engineering. The governing equations of toroidal shells are very complicated because of its variable coefficients with singularity. To find their analytical solution, traditionally, the complex form governing equations were proposed and some useful solutions were obtained. Unfortunately, no any closed-form solution has even been obtained for either general or slender toroidal shells. This paper focus on a special case of toroidal shells, i.e., slender symmetrical toroidal shells. For the first time, the closed-form solution of this kind of shell has been successfully obtained from displacement form governing equations. The closed-form solution is demonstrated for the example of thermal compensation devices. The correction of well-known Dahl formula for slender toroidal shell has been proposed based on the solution obtained in this paper.

A semi-analytical thermoelasticity solution for hollow and solid rotating axisymmetric disks made of functionally graded materials is presented. The radial domain is divided into some virtual sub-domains in which the power-law distribution is used for the thermomechanical properties of the constituent components. Imposing the necessary continuity conditions between adjacent sub-domains, together with the global boundary conditions, a set of linear algebraic equations are obtained. Solution of the linear algebraic equations yields the thermoelastic responses for each sub-domain as exponential functions of the radial coordinate. Some results for the stress, strain and displacement components along the radius are presented due to centrifugal force and thermal loading. Results obtained within this solution are compared with those of a finite element analysis in the literature. Based on the results, it is shown that the property gradation correlates with thermomechanical responses of FG disks.

An unsteady mathematical model to study the characteristics of blood flowing through an arterial segment in the presence of a couple of stenoses with surface irregularities is developed. The flow is treated to be axisymmetric, with an outline of the stenoses obtained from a three dimensional casting of a mildly stenosed artery [1], so that the flow effectively becomes two-dimensional. The governing equations of motion accompanied by appropriate choice of boundary and initial conditions are solved numerically by MAC (Marker and Cell) method in cylindrical polar coordinate system in staggered grids and checked numerical stability with desired degree of accuracy. The pressure-Poisson equation has been solved by successive-over-relaxation (SOR) method and the pressure-velocity correction formulae have been derived. The flexibility of the arterial wall has also been accounted for in the present investigation. Further, in-depth study in the flow pattern reveals that the separation Reynolds number for the multi-irregular stenoses is lower than those for cosine-shaped stenoses and a long single irregular stenosis. The present results predict the excess pressure drop across the cosine stenoses than the irregular ones and show quite consistency with several existing results in the literature which substantiate sufficiently to validate the applicability of the model under consideration.

Collective Vibrations of nuclei far from the valley of stability are investigated within the quasi-particle random phase approximation based on relativistic Hartree-Bogoliubov theory with non-linear meson couplings. Pairing correlations are described in by a finite range effective particle-particle interaction of Gogny type. The quasi-particle random phase equations are solved in the canonical basis and collective strength distributions are discussed.

To analyse the mechanics of extrusion of an axi-symmetric tube starting from either a hollow or a solid circular billet, a generalised analytical approach based on the slab method of analysis is developed for a somewhat general case of tube extrusion through a general pro"le-shaped die and over a general pro"le-shaped mandrel. The results of mean extrusion pressures obtained from the theoretical analysis for the various die}mandrel combinations are compared with the experimental investigation carried out on a model material and with the work of other authors. These show reasonably good agreements. 2001 Elsevier Science Ltd. All rights reserved.

The shielding performance of perforated magnetic shields for electric power applications is described. The shielding of an axisymmetric induction heating device is studied as a function of frequency, number of perforations and dimensions of the perforations. From the numerical point of view, the perforations cause the numerical model to be 3D. A numerical optimisation is carried out to find the optimal geometry with respect to the shielding factor and the volume of the shield. For the optimisation, two approaches are presented. The first approach is fast and easy-to-implement, but has limited accuracy. It uses a classical 2D axisymmetric model where the perforations are approximated by 'axisymmetric air gaps' resulting in a segmented shield. It is shown how to modify the 2D model to obtain results that are similar to the ones of a 3D model. The second approach is more accurate although quite fast, but more difficult to implement. It combines a 3D thinshell finite element model with the unmodified 2D model in a space mapping optimisation algorithm. The validation of both models is based on experimental work for an unperforated shield and for the optimised perforated shield.

The self-gravitating instability of a fluid cylinder pervaded by magnetic field and endowed with surface tension has been discussed. The dispersion relation is derived and some reported works are recovered as limiting cases from it. The capillary force is destabilizing only in the small axisymmetric domain and stabilizing otherwise. The magnetic field has a strong stabilizing effect in all modes of perturbation for all wavelengths. The self-gravitating force is destabilizing in the axisymmetric perturbation. However the magnetic field effect modified a lot the destabilizing character of the model and could overcome the capillary and self-gravitating instability of the model for all short and long wavelengths.

We consider axially symmetric static metrics in arbitrary dimension, both with and without a cosmological constant. The most obvious such solutions have an SO(n) group of Killing vectors representing the axial symmetry, although one can also consider abelian groups which represent a flat 'internal space'. We relate such metrics to lower dimensional dilatonic cosmological metrics with a Liouville potential. We also develop a duality relation between vacuum solutions with internal curvature and those with zero internal curvature but a cosmological constant. This duality relation gives a solution generating technique permitting the mapping of different spacetimes. We give a large class of solutions to the vacuum or cosmological constant spacetimes. We comment on the extension of the C-metric to higher dimensions and provide a novel solution for a braneworld black hole.

We examine the internal flow of viscoplastic liquids through ducts consisting of an abrupt axisymmetric expansion followed by an abrupt contraction. Steady, inertialess numerical solutions were obtained by solving the conservation equations of mass and momentum via the finite volume method. The viscoplastic behavior of the liquid was modeled by the generalized Newtonian liquid model with a recently proposed viscosity function. Flow visualization experiments were also conducted with Carbopol aqueous solutions at different concentrations. Yield surfaces delimiting yielded and unyielded regions were observed for different combinations of the governing parameters. The unyielded region is located in the largediameter portion of the channel, near the wall. The size of the unyielded region is shown to be a strong function of the geometrical, rheological, and flow parameters.

In this article, we investigate the response of a thin superconducting shell to an arbitrary external magnetic field. We identify the intensity of the applied field that forces the emergence of vortices in minimizers, the so-called first critical field H c1 in Ginzburg-Landau theory, for closed simply connected manifolds and arbitrary fields. In the case of a simply connected surface of revolution and vertical and constant field, we further determine the exact number of vortices in the sample as the intensity of the applied field is raised just above H c1. Finally, we derive via Γ-convergence similar statements for three-dimensional domains of small thickness, where in this setting point vortices are replaced by vortex lines.

It is possible to construct a special family of nonextremal black hole microstates. These microstates are unstable, and emit radiation at a rate which is found to exactly equal the Hawking radiation rate predicted for them by the dual CFT. In this paper we analyze in more detail the nature of the radiation created by these unstable modes. The energy and angular momentum of the mode is found to be localized in two regions: one near infinity corresponding to the emitted quanta, and the other in the ergoregion which is deep inside the interior of the geometry. The energy and angular momenta are equal and opposite for these two contributions, as expected for emission from ergoregions. We conjecture that more general nonextremal microstates will possess ergoregions (with no axial symmetry), and radiation from these regions can be part of the general Hawking emission for the microstates.

We present a study of the Earth's rotational motion in terms of the Earth Orientation Parameters (EOP) of the new paradigm that is recommended by the IAU 2000 resolutions to transform between the celestial and terrestrial reference systems. This paper presents the first part of the study whose purpose is to establish the dynamical equations of the rotation of a rigid Earth as a function of these new parameters. Starting from Euler dynamical equations for a rigid Earth, and using expressions for the components of the instantaneous rotation vector as functions of the celestial coordinates X, Y of the Celestial intermediate pole (CIP) and of the Earth rotation angle (ERA), the equations of Earth rotation were obtained explicitly in terms of those parameters. Taking into account the order of magnitude of the terms of these equations, we obtain the most appropriate form of the equations for a practical integration. We then investigated the possible methods of integration for providing semi-analytical solutions for the X and Y variables in the axially symmetric case. We also perform a number of tests regarding the efficiency of these methods, based on the IAU 2000 precession-nutation. We extended this approach to a deformable Earth, based on integration constants compliant with the new P03 precession model.

The present study focuses on two kinds of reconstruction methods designed to capture the dynamic loads acting on the reattaching part of an axisymmetric step flow. The pressure signals on discrete points of the geometry constitute the starting point of this study. Data are taken from a validated numerical simulation in order to maximize the number of sensors at the wall. First, an a priori methodology for the load reconstruction without any hypothesis on the flow behaviour is exposed. The influence of the number of sensors and their spatial distribution over the geometry is investigated. It is shown that azimuthal and longitudinal resolution have different effects on the reconstructed power spectral density of the load. Then, it is found that an experimental process with few unsteady sensors cannot provide an accurate prediction of the load. Then a second kind of reconstruction method based on the physical knowledge of the flow is presented. The original Nguyen approach initially developed for internal side loads is optimized with a spatial analysis and gives a satisfactory prediction of the load with only a minimal number of sensors.

Ultimate capacity of large diameter bored piles is usually determined from pile loading tests as recommended by several international codes and foundation design standards. However, loading of this type of piles till achieving apparent failure is practically seldom. In this paper, numerical analyses are carried out to simulate load test of a large diameter bored pile performed at the location of Alzey highway bridge project (Germany). Test results of pile load settlement relationship till failure as well as results of the base and shaft resistances are available. Apparent failure was indicated in this test by the significant increase of the induced settlement during the last load increment applied on the pile head. Measurements of this pile load test are used to assess the quality of the numerical models investigated. Three different material soil models are implemented in the analyses: Mohr coulomb (MC), Soft soil (SS), and Modified Mohr coulomb (MMC). Very good agreement is obtain...

We study the motion of a test particle in a stationary, axially and reflection symmetric spacetime of a central compact object, as affected by interaction with a test radiation field of the same symmetries. Considering the radiation flux with fixed but arbitrary (non-zero) angular momentum, we extend previous results limited to an equatorial motion within a zero-angularmomentum photon flux in the Kerr and Schwarzschild backgrounds. While a unique equilibrium circular orbit exists if the photon flux has zero angular momentum, multiple such orbits appear if the photon angular momentum is sufficiently high.

A compact ultrawideband antenna with hemispherical helical geometry is proposed and investigated both theoretically and experimentally. The radiating element of this antenna consists of a tapered metallic strip that assumes a non-conformal orientation relative to the hemispherical surface in order to yield maximum bandwidth. The number of turns is about four and half with a constant spacing between them. The antenna is fed by a coaxial cable with the inner conductor connected to the radiating strip through a matching section, and its outer conductor connected to a ground plane. Radiation properties of the proposed hemispherical helical antenna, including far-field patterns, axial ratio, directivity, input impedance and voltage standing wave ratio (VSWR), are studied numerically and evaluated experimentally. Simulation and measured results are in good agreement. This design provides a maximum directivity of 9 1 dB, a VSWR 2 (relative to a 50 reference impedance), and nearly equal E-and H-plane far-field patterns with high degree of axial symmetry over a bandwidth of more than 50%. Also, over a bandwidth of about 24% the axial ratio remains below 3 dB. The compact size and ultrawideband performance of this antenna make it advantageous for high speed wireless communication systems and avionics. Index Terms-Hemispherical helical antennas, low profile antennas, spherical helix, ultrawideband antennas.

The study of the mol. structure of new thorium/uranium fullerene compds., Th@C82 and U@C84, is reported. Th@C84 and U@C82 were prepd. by an actinide-fullerene reactor under He gas and 400 Torr pressure using 110A arc discharge. XAFS spectra showed the oxidn. no. of uranium in the cage of C82 is 3+. 13C-NMR spectra of Th@C84 gave 11 peaks, which is the same with the simulation result showing that D2d symmetry is the only possible structure for Th@C84. The expts. showed two possible isomers for D2d symmetry, one is satisfied with Isolated Pentagon Rule (IPR), the other is not but with C2 axis. Thus, it is clear that the actinide metal stabilized fullerene Th@C84 has D2d symmetry. [on SciFinder(R)]

A large sample with the full space motions drawn from the Hipparcos Catalogue allows us to select some nested subsamples containing an increasing number of thick disk stars. Segregated thick disk populations show a progressive decreasing vertex deviation according to a trend of axial symmetry, as well as an increasing velocity dispersion and mean age, which are consistent with a trend of steady state. Thus, we propose to extrapolate the oldest thick disk by using a quite general kinematic model, that is time dependent and with point-to-point axial symmetry, until reaching a hypothetical stellar population with axial symmetry, vanishing radial differential movement, and steady state. In the Galactic plane, the extrapolated population determines the point of the velocity space with differential rotation alone, that is with no net radial motion. The present work improves the estimation of the local radial mean velocity that we obtained in a previous work, where a raw linear extrapolation was performed. Now we complete the analysis by using a more precise estimation based on the kinematic model. The resulting no net radial motion point has radial heliocentric velocity U=-20 ± 1 km s-1 and rotation heliocentric velocity V=-82 ± 2 km s-1. During the disk heating process, the disk populations lose angular momentum and radial motion while increasing the velocity dispersion. And, in particular, the thick disk loses its total radial motion before reaching the steady state, in an attempt to recover axiality. The new estimation stresses previous conclusions about the vanishing radial mean velocity of the stars associated with the Hyades-Pleiades supercluster, originated by large molecular clouds.

In this Letter, we present analytical and numerical solutions for an axis-symmetric diffusion-wave equation. For problem formulation, the fractional time derivative is described in the sense of Riemann-Liouville. The analytical solution of the problem is determined by using the method of separation of variables. Eigenfunctions whose linear combination constitute the closed form of the solution are obtained. For numerical computation, the fractional derivative is approximated using the Grünwald-Letnikov scheme. Simulation results are given for different values of order of fractional derivative. We indicate the effectiveness of numerical scheme by comparing the numerical and the analytical results for α = 1 which represents the order of derivative.

This paper presents the development of a semi-analytical axisymmetric shell finite element model with piezoelectric layers using the 3D linear elasticity theory. The piezoelectric effect of the material could be used as sensors and/or actuators in way to control shell deformation. In the ...