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The ability to manipulate biological cells and micrometer-scale particles plays an important role in many biological and colloidal science applications. However, conventional manipulation techniques, such as optical forces, electrokinetic forces (electrophoresis, dielectrophoresis (DEP), and traveling-wave dielectrophoresis), magnetic forces, acoustic forces (surface standing acoustic waves (SAW), and bulk standing acoustic waves(BAW)), and hydrodynamic flows, cannot achieve high resolution and high throughput at the same time. While electrokinetic forces and other mechanisms provide higher throughput than optical mechanism, but lack the flexibility or the spatial resolution necessary for controlling individual particles. None of which could provide high resolution, throughput and versatility in clinical applications.In this dissertation, I present a novel DEP concept for high resolution, throughput and versatility microns-sized particle and biological cell manipulation in high-speed flows. Using novel three-dimensional (3D) polydimethylsiloxane (PDMS) thin-film fabrication platform I developed, true heterogeneous integration of electronics on hard substrates (silicon and/or glass) and PDMS are demonstrated for the first time to create 3D electric field across the entire large area (couple centimeter across) 3D microfluidic channel networks. Which enables broad applications, such as sheathless sub-micron particle focusing in high-speed flows, tunable micron-sized particle and cell focusing in high-speed flows, and ultra-high precision particle size-based sorting. Within all sections, experiments were performed with beads to verify the concept of each platform and then with cells to demonstrate qualitative and quantitative operation of the performance. These technologies is now well poised to enable the development of biological assays that are currently unavailable.

Because of rising traumatic accidents and diseases, the number of patients suffering from nerve injury is increasing. Without effective rehabilitation therapy, the patients will get motor or sensory function losses or even a lifelong disability. As for amputees, neural interface technology can be used to splice nerves and electrical wires together in a way that allows them to control an artificial limb as if it was a natural extension of the body. However, the means the need for an autologous nerve to stimulate axonal regeneration and extension into target tissues, which are limited by the supply of donor nerves. Based on the principle of mechanical force regulating axon growth, in this paper, we developed a three-dimensional nerve stretch growth device for an implantable neural interface. The device consists of three motors controlled by single chip microcomputer and some mechanical parts. The stability and reliability of the device were tested. Then, we used neurons derived from human pluripotent stem cells by small chemical molecules to explore the optimal three-dimensional stretch culture parameters. Furthermore, we found that the axons were intact through 10 rotations per day and 1 mm of horizontal pulling per day. The results of this research will provide convenience for patients treated through an implantable neural interface.

The current investigation focused on the development of effective and suitable modelling of reinforced concrete component with and without strengthening. The modelling includes physical and constitutive models. New interface elements have been developed, while modified constitutive law have been applied and new computational algorithm is utilised. The new elements are the Truss-link element to model the interaction between concrete and reinforcement bars, the interface element between two plate bending elements and the interface element to represent the interfacial behaviour between FRP, steel plates and concrete. Nonlinear finite-element (FE) codes were developed with pre-processing. The programme was written using FORTRAN language. The accuracy and efficiency of the finite element programme were achieved by analyzing several examples from the literature. The application of the 3D FE code was further enhanced by carrying out the numerical analysis of the three dimensional finite element analysis of FRP strengthened RC beams, as well as the 3D non-linear finite element analysis of girder bridge. Acceptable distributions of slip, deflection, stresses in the concrete and FRP plate have also been found. These results show that the new elements are effective and appropriate to be used for structural component modelling.

This paper presents direct numerical simulations (DNS) of fully developed turbulent liquid-metal flow in a circular duct entering a magnetic field. The case of a magnetohydrodynamic flow leaving a strong magnetic field has been extensively studied experimentally and numerically owing to its similarity to typical flow configurations appearing in liquid metal blankets of nuclear fusion reactors. Although also relevant to the design of fusion reactor blankets, the flow entering the fringing field of a magnet remains unexplored because its high intricacy precludes any simplification of the governing equations. Indeed, the complexity of the magnetohydrodynamic-turbulence interaction can only be analysed by direct numerical simulations or experiments. With that purpose, this paper addresses the case of a fully developed turbulent flow (Re τ ≈ 520) entering low, intermediate and strong magnetic fields under electrically insulating and poorly conducting walls by means of three-dimensional direct numerical simulations. Purely hydrodynamic computations (without the effect of the magnetic field) reveal an excellent agreement against previous experimental and numerical results. Current MHD results provide a very detailed information of the turbulence decay and reveal new three-dimensional features related to liquid-metal flow entering strong increasing magnetic fields, such as flow instabilities due to the effect of the Lorentz forces within the fringing region at high Ha numbers. © 2013 Elsevier B.V. © 2013 Published by Elsevier B.V. 88 3108 3124 3108-3124

A 3D two-cell representation of laminates with periodic fiber arrays is established and the corresponding periodic boundary conditions are presented. The matrix is described by a nonlinear viscoelastic material model and the fiber by an elastic one. Matrix cracking is modeled by a "smeared crack" method. The modeling of material nonlinearity, crack initiation, and growth, with appropriate periodic boundary conditions, are incorporated into a finite element model (FEM). Numerical results for five different angle-ply laminates under tensile loading are presented. The results are found to be in fair agreement with the available test data. © 2013 Taylor and Francis Group, LLC.

In the current study, the effect of the thickness and the foam density in three-dimensional integrated woven sandwich composites on quasi-static mechanical properties under three-point bending was investigated. Bending modulus and core shear modulus were determined by subjecting the samples, which were cut with varying span lengths according to their core thicknesses, to three-point bending test. Obtained results were optimized by taking core thickness, foam density and panel weights into consideration. Damages that occurred on the tested samples were reported. When compared to conventional foam core sandwich composites, it was found that three-dimensional integrated sandwich composites have superior mechanical properties and due to the fact that the pile yarns in the core and the foam support each other, contrary to conventional sandwich composites no catastrophic core breakage occurs under load, thus the load bearing capacity of the structure is sustained. ispartof: Journal of Reinforced Plastics and Composites vol:32 issue:9 pages:664-678 status: published

Sixteen propellant formulations based on ammonium perchlorate (AP), hydroxyl-terminated polybutadiene, and aluminium particles have been tested for size distribution of aluminium agglomerates emerging from their burning surface. The formulations are based on a bimodal size distribution of AP particles. Ten of the formulations exhibit one or two plateaus/mesa in their burning rate variation with pressure (zero/negative pressure exponent of burning rate). The relevant formulation variables, namely, coarse and fine AP sizes and coarse-to-fine ratio, aluminium size and content, and two different curing agents, have been varied. Tests are performed in the 1-10 MPa pressure range. A direct correlation between burning rate and agglomerate size exists for propellants with normal burning rate trends but a neutral or inverse correlation is observed for those exhibiting plateau burning behaviour. Larger the parent aluminium size, lesser the agglomeration, as expected; but the effect of aluminium content is non-monotonic. The coarse AP size influences the aluminium agglomerate size as expected from the pocket model regardless of plateau burning effects. The agglomerate size decreases with increase in fine AP size, however. A computer model developed earlier at this laboratory for prediction of aluminium agglomerates based on three-dimensional packing of particles and deduction of AP particles with attached leading edge diffusion flames is applied to the present formulations. The model under-predicts the agglomerate size, only marginally for propellants that do not exhibit plateau burning rate trends, but substantially, otherwise. This is because it does not take into account effects of binder melt flow and is independent of the curing agent of the binder. � 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

In the current study, the effect of the thickness and the foam density in three-dimensional integrated woven sandwich composites on quasi-static properties was investigated. For this purpose, produced samples were subjected to uniaxial flatwise compression tests and their compression strength and moduli were determined. Obtained results were optimized by taking core thickness, foam density and panel weights into consideration. Damages that occurred on the tested samples were reported. When compared to conventional foam core sandwich composites, it was found that three-dimensional integrated sandwich composites have better compression properties and due to the fact that the pile yarns in the core and the foam support each other.

PurposeThe purpose of this paper is to develop an algorithm, using PCA‐based neural network, to retrieve the vertical rainfall structure in a precipitating atmosphere. The algorithm is powered by a rigorous solution to the plane parallel radiative transfer equation for the atmosphere with thermodynamically consistent vertical profiles of humidity, temperature and cloud structures, together with “measured” vertical profiles of the rain structure derived from a radar.Design/methodology/approachThe raining atmosphere is considered to be a plane parallel, radiatively participating medium. The atmospheric thermodynamic profiles such as pressure, temperature and relative humidity along with wind speed at sea surface and cloud parameters corresponding to Nargis, a category 4 tropical cyclone that made its landfall on May 2, 2008 at the Republic of Myanmar, are obtained by solving the flux form of Euler's equations in three‐dimensional form. The state‐of‐the‐art community software Weather Research and Forecasting has been used for solving the set of equations. The three‐dimensional rain profiles for the same cyclone at the same instant of time are obtained from National Aeronautics and Space Administration's space borne Tropical Rainfall Measuring Mission's precipitation radar over collocated pixels. An in‐house Micro‐Tropiques code is used to perform radiative transfer simulations for frequencies corresponding to a typical space borne radiometer, and hence to generate the database which is later used for training the neural network. The back propagation‐based neural network is optimized with reduced number of parameters using principal component analysis (PCA).FindingsThe results show that neural network is capable of retrieving the vertical rainfall structure with a correlation coefficient of over 0.99. Further, reducing the ill‐posedness in retrieving 56 parameters from just nine measurements using PCA has improved the root mean square error in the retrievals at reduced computational time.Originality/valueThe paper shows that combining numerically generated atmospheric profiles together with radar measurements to serve as input to a radiative transfer model brings in the much‐required synergy between numerical weather prediction, radar measurements and radiative transfer. This strategy can be gainfully used in satellite meteorology. Using principal components to reduce the ill‐posedness, thereby increasing the robustness in retrieving vertical rain structure, has been attempted for the first time. A well‐trained network can be used as one possible option for an operational algorithm for the proposed Indian climate research satellite Megha‐Tropiques, due to be launched in early 2011.

The purpose of this research is to analyse the influence of steering control devices for disabled people on passive safety. It is based on the advances made in the modelling and simulation of the driver position and in the suit verification test. The influence of these devices is studied through airbag deployment and/or its influence on driver safety. We characterise the different adaptations that are used in adapted cars that can be found mounted in vehicles in order to generate models that are verified by experimental test. A three-dimensional design software package was used to develop the model. The simulations were generated using a dynamic simulation program employing LS-DYNA finite elements. This program plots the geometry and assigns materials. The airbag is shaped, meshed and folded just as it is mounted in current vehicles. The thermodynamic model of expansion of gases is assigned, and the contact interfaces are defined. Static tests were carried out on the deployment of the airbag to contrast with and to validate the computational models and to measure the behaviour of the airbag when there are steering adaptations mounted in the vehicle. © 2011 Taylor & Francis.

Recently, stereolithography, one of the rapid prototyping (RP) techniques, has simplified the process of making three-dimensional (3-D) photoelastic models. One of the issues in stereolithography-made models is the noise due to porosity of the model. This is undesirable for data handling in digital photoelasticity. A preliminary study showed that the thickness of the slice has an influence on the appearance on the noise. In this paper, use of 10-step phase-shifting technique (PST) and refined three-fringe photoelasticity (RTFP) is explored to determine the isochromatic data as accurately as possible. A slice cut from a 3-D model of a spline shaft made of stereolithographic material is used for isochromatic determination. It is found that with suitable postprocessing, the quantitative results obtained from 10-step PST and RTFP are comparable. The relative merits of these two techniques for analysing stereolithographic models are brought out. � 2011, Society for Experimental Mechanics.

This paper presents an algorithm for generating the Interior Medial Axis Transform (iMAT) of 3D objects with free-form boundaries. The algorithm proposed uses the exact representation of the part and generates an approximate rational spline description of the iMAT. The algorithm generates the iMAT by a tracing technique that marches along the object's boundary. The level of approximation is controlled by the choice of the step size in the tracing procedure. Criteria based on distance and local curvature of boundary entities are used to identify the junction points and the search for these junction points is done in an efficient way. The algorithm works for multiply-connected objects as well. Results of the implementation are provided. (C) 2010 Elsevier Ltd. All rights reserved.

In this numerical study, supersonic combustion of liquid kerosene in a strut-based combustor is investigated. To this end, three-dimensional compressible, turbulent, nonreacting and reacting flow calculations with a single-step chemistry model have been carried out. For the nonreacting flow calculations, fuel droplet trajectories, degree of mixing, and mixing efficiency are presented and discussed. For the reacting flow calculations, contours of heat release and Mach number and the variation of combustion efficiency, total pressure loss, and thrust profile along the combustor length are used to identify the regions of mixing and heat release inside the combustor. Furthermore, the predicted variation of static pressure along the combustor top wall is compared with experimental data. The significance of the lateral spread of the fuel and the extent of the mixing process, especially for a liquid fuel such as kerosene, on the prediction of heat release is discussed in detail. Copyright � 2010 by Luca Boccaletto.

In this study, a three-dimensional transient numerical analysis was performed inside the automobile cabin during heating period. A three-dimensional vehicle cabin including glazing surfaces was modeled by using the real dimensions of a car. A virtual manikin with real dimensions and physiological shape was added to the model of the vehicle cabin. It was assumed that the manikin surfaces were subjected to either constant heat flux or constant temperature. Three-dimensional fluid flow, temperature distribution, and heat transfer characteristics inside the cabin were calculated. Experimental measurements were also conducted. Comparisons of the results were presented and discussed. The results of numerical calculations were in good agreement with the experimental and theoretical data in the literature. FIAT-TOFAS

Al70Y16Ni10Co4 glassy powder was produced by mechanical alloying of elemental powder mixtures and the thermal stability as well as the crystallization kinetics was investigated using differential scanning calorimetry in both isochronal and isothermal modes. The isochronal and isothermal activation energies have a similar value (?280 kJ/mol). Similar activation energy was obtained for the process from the viscosity measurements. In addition, JMA analysis shows that the transformation is diffusion controlled three-dimensional process and the crystallization proceeds with increasing nucleation rate at annealing temperatures within the supercooled liquid region, while it proceeds with decreasing nucleation rate at temperatures below the glass transition temperature. Metal matrix composites were synthesized through powder metallurgy methods by hot extrusion of commercial 6061 Al alloy powder blended with different amounts of Al70Y16Ni10Co4 metallic glass reinforcement. The mechanical properties of the 6061 matrix are remarkably improved by the addition of the glass reinforcements. The ultimate compressive strength increases from 260 MPa for the 6061 alloy to 350 MPa for the composite with 50 vol.% of glassy phase. � 2008 Elsevier B.V. All rights reserved.

In this numerical study, supersonic combustion of kerosene in three model combustor configurations is investigated. To this end, 3-D, compressible, turbulent, nonreacting, and reacting flow calculations with a single step chemistry model have been carried out. For the nonreacting flow calculations, the droplet diameter distribution at different axial locations, variation of the Sauter mean diameter, and the mixing efficiency for three injection pressures are presented and discussed. In addition, the effect of turbulent dispersion on the mixing efficiency is studied using a stochastic model in conjunction with the two-equation shear stress transport ?-? turbulence model. For the reacting flow calculations, contours of heat release and axial velocity at several axial locations are used to identify regions of heat release inside the combustor. Combustion efficiency predicted by the present results is compared with earlier predictions for all the combustor models. Furthermore, the predicted variation of static pressure along the combustor top wall is compared with experimental data reported in the literature. Calculations show that the penetration and spreading of the fuel increases with an increase in the injection pressure. Predicted values of the combustion efficiency are more realistic when the spray model is used for modelling the injection of the fuel. The importance of the mixing process, especially for a liquid fuel such as kerosene, on the prediction of heat release is discussed in detail.

This paper presents a three-dimensional finite element analysis of the response of piles to inclined uplift loads. It deals with the influence of the soil-pile interface on this response. Calculations are carried out for several load’s inclinations and different conditions at the soil-pile interface. The concept of the “critical depth” at the soil-pile interface is investigated. Analyses show that the lateral behaviour of the pile is independent from both the load’s inclination and the interface condition, while both the load’s inclination and the soil-pile interface largely affect the axial response of piles.

A multiscale methodology has been developed for modeling mechanical behavior of collagen fiber networks. The methodology addresses scale separation between the macroscopic, tissue-level scale and the microscopic, fiber-level scale. A three-dimensional, Galerkin finite-element model has been employed for the macroscopic scale, while the tissue microstructure is represented as a three-dimensional fibrillar network. The model was applied to a rectangular slab in uniaxial extension. A heterogeneous microstructure resulted in a non-uniform deformation field, and Poisson's ratio varied for networks with different alignments. The model was also specified and compared to published data relating microstructure to macroscopic behavior of collagen gels. © 2007 Elsevier B.V. All rights reserved. 196 2981 2990 2981-2990

Here we investigate the practical feasibility of performing soundfield reproduction throughout a three-dimensional area by controlling the acoustic pressure measured at the boundary surface of the volume in question. The main aim is to obtain quantitative data showing what performances a practical implementation of this strategy is likely to yield. In particular, the influence of two main limitations is studied, namely the spatial aliasing and the resonance problems occurring at the eigenfrequencies associated with the internal Dirichlet problem. The strategy studied is first approached by performing numerical simulations, and then in experiments involving active noise cancellation inside a sphere in an anechoic environment. The results show that noise can be efficiently cancelled everywhere inside the sphere in a wide frequency range, in the case of both pure tones and broadband noise, including cases where the wavelength is similar to the diameter of the sphere. Excellent agreement was observed between the results of the simulations and the measurements. This method can be expected to yield similar performances when it is used to reproduce soundfields., 28 pages de texte

In this article, static analysis of functionally graded, anisotropic and linear magneto-electro-elastic plates have been carried out by semi-analytical finite element method. A series solution is assumed in the plane of the plate and finite element procedure is adopted across the thickness of the plate such a way that the three-dimensional character of the solution is preserved. The finite element model is derived based on constitutive equation of piezomagnetic material accounting for coupling between elasticity, electric and magnetic effect. The present finite element is modeled with displacement components, electric potential and magnetic potential as nodal degree of freedom. The other fields are calculated by post-computation through constitutive equation. The functionally graded material is assumed to be exponential in the thickness direction. The numerical results obtained by the present model are in good agreement with available functionally graded three-dimensional exact benchmark solutions given by Pan and Han [Pan, E., Han, F., in press. Green’s function for transversely isotropic piezoelectric functionally graded multilayered half spaces. Int. J. Solids Struct.]. Numerical study includes the influence of the different exponential factor, magneto-electro-elastic properties and effect of mechanical and electric type of loading on induced magneto-electro-elastic fields. In addition further study has been carried out on non-homogeneous transversely isotropic FGM magneto-electro-elastic plate available in the literature [Chen, W.Q., Lee, K.Y., Ding, H.J., 2005. On free vibration of non-homogeneous transversely isotropic magneto-electro-elastic plates].

The present study focuses on the study of topological properties of flow in a turbine cascade. Critical-point theory is used to explain the flow phenomenon. Examination and analysis of skin-friction line patterns on three-dimensional bodies such as turbine cascade, compressor cascade, cylinder, etc. enables enhanced understanding of the three-dimensional flow. Topology of flow means types of critical points formed, their interconnection, and relation between numbers of different types of critical points. Present work focuses on rules with regard to the topological consistency of a flow field. It consists of two parts, one is the connectivity of different critical points, and another is deriving the relation between the number of nodal and saddle points of a tangent vector field. Relation between the number of nodal and saddle points is derived for flows such as a turbine cascade with and without tip clearance, turbine cascade with the end wall fence, flow over a three-dimensional obstacle, etc. Relevant mathematical background necessary for derivation is discussed. The results derived for the turbine cascade is independent of the end wall contouring, leading edge modification, trailing edge modification, and blade shape. The derived relations also hold for a compressor cascade. Flow visualization based on CFD calculations is presented for the turbine cascade with and without an end wall fence.

It is a challenge to meld the energy of secondary batteries with the power of supercapacitors. Herein, we created electrodes finely tuned for this purpose, consisting of a monolayer of MnO nanocrystallites mechanically anchored by pore-surface terminations of 3D arrays of graphene-like carbon nanosheets ("3D-MnO/CNS"). The biomass-derived carbon nanosheets should offer a synthesis cost advantage over comparably performing designer nanocarbons, such as graphene or carbon nanotubes. High Li storage capacity is achieved by bulk conversion and intercalation reactions, while high rates are maintained through stable ∼20 nm scale diffusion distances. For example, 1332 mAh g -1 is reached at 0.1 A g-1, 567 mAh g-1 at 5 A g-1, and 285 mAh g-1 at 20 A g-1 with negligible degradation at 500 cycles. We employed 3D-MnO/CNS (anode) and carbon nanosheets (cathode) to create a hybrid capacitor displaying among the most promising performances reported: based on the active materials, it delivers 184 Wh kg-1 at 83 W kg-1 and 90 Wh kg-1 at 15-000 W kg-1 with 76% capacity retention after 5000 cycles. © 2014 American Chemical Society.

Polymer Electrolyte Membrane (PEM) fuel cell is a promising energy conversion device with applications involving rapid start-up and low operating temperature. Proper cooling of PEM fuel cell stack is an essential requirement in ensuring its durability for which separate cooling channels between each cell are often used. This study involves a detailed three-dimensional numerical investigation on cooling channel designs based on traditional serpentine and spiral designs. Four new designs - divided serpentine, divided spiral, distributed serpentine and distributed spiral are proposed to predict the fluid flow and thermal characteristics. An in-house code based on Streamline upwind/Petrov Galerkin finite element method is used to solve the three-dimensional governing equations. Simulations are carried out for Reynolds number ranging from 415 to 1247. Results indicate that the novel designs have better performance compared to serpentine in terms of uniformity in temperature distribution at all Re. The merits and demerits of all the designs in terms of maximum and average temperature on the cooling plate is also discussed. The pressure drop required to drive the flow is higher in the spiral and new designs compared to serpentine due to the presence of complex turns. � 2014 Elsevier Ltd. All rights reserved.

In the field of fluid mechanics, the resolution of computational schemes has outpaced experimental methods and widened the gap between predicted and observed phenomena in fluid flows. Thus, a need exists for an accessible method capable of resolving three-dimensional (3D) data sets for a range of problems. We present a novel technique for performing quantitative 3D imaging of many types of flow fields. The 3D technique enables investigation of complicated velocity fields and bubbly flows. Measurements of these types present a variety of challenges to the instrument. For instance, optically dense bubbly multiphase flows cannot be readily imaged by traditional, non-invasive flow measurement techniques due to the bubbles occluding optical access to the interior regions of the volume of interest. By using Light Field Imaging we are able to reparameterize images captured by an array of cameras to reconstruct a 3D volumetric map for every time instance, despite partial occlusions in the volume. The technique makes use of an algorithm known as synthetic aperture (SA) refocusing, whereby a 3D focal stack is generated by combining images from several cameras post-capture (1). Light Field Imaging allows for the capture of angular as well as spatial information about the light rays, and hence enables 3D scene reconstruction. Quantitative information can then be extracted from the 3D reconstructions using a variety of processing algorithms. In particular, we have developed measurement methods based on Light Field Imaging for performing 3D particle image velocimetry (PIV), extracting bubbles in a 3D field and tracking the boundary of a flickering flame. We present the fundamentals of the Light Field Imaging methodology in the context of our setup for performing 3DPIV of the airflow passing over a set of synthetic vocal folds, and show representative results from application of the technique to a bubble-entraining plunging jet.

Computational predictions concerning ballooning of multiple fuel pins during a loss of coolant accident (LOCA) with a final reflood phase are now more than ever of interest amongst the design basis accidents in pressurized water reactors (PWR). Difficulties for such studies are twofold. Firstly, modeling has to take into account many coupled phenomena as thermics (heat generation, radiation, convection and conduction), hydraulics (multi-dimensional one-to-three phase flow and shrinkage) and mechanics (thermal expansion, creep and embrittlement) but also chemistry (oxidation, hydriding, etc.). Secondly, there exists only a few experimental investigations to validate the complex coupled modeling enabling such predictions. This paper deals with the new computational 3D tool named DRACCAR which models the deformations of rods within a bundle (from one rod to a full fuel assembly) during LOCA transients including the water reflood phase. © 2012 Elsevier B.V. All rights reserved.

This paper presents three-dimensional direct numerical simulations of liquid metal flow around a circular cylinder placed symmetrically in a rectangular duct, under a wide range of magnetic field intensities. Results are presented for values of the Hartmann number (based on the duct width) in the range of 0 ≤ Ha ≤ 1120, and the Reynolds number (based on the cylinder diameter and centerline velocity) in the range 0 ≤ Rec ≤ 5000. The generated flow regimes and the associated critical values of parameters are investigated in detail through full three-dimensional simulations. The effect of the magnetic field on the wake structure is discussed in relation to the possible mechanisms for the generation or suppression of vortices, and to previous attempts to model magnetohydrodynamic flows using simplified two-dimensional models. Present results reveal a non-monotonic dependance of the critical Reynolds number for the onset of vortex shedding, with respect to the Hartmann number. For certain combinations of Ha and Re values, this work confirms the onset of a new flow regime, the existence of which has been recently suggested based on quasi-two-dimensional simulations. Unexpectedly, the spanwise distribution of the force coefficients along the cylinder is found to become more three-dimensional with increasing Ha. Furthermore, the three-dimensional nature of the present simulations reveals additional counter-intuitive features of the new regime that could not possibly had been captured by quasi-two-dimensional models. One such feature, shown here for the first time, is an increase in the flow unsteadiness with increasing intensity of the magnetic field. © 2013 Author(s). 25

We couple collocated isogeometric boundary element methods and unstructured analysis-suitable T-spline surfaces for linear elastostatic problems. We extend the definition of analysis-suitable T-splines to encompass unstructured control grids (unstructured meshes) and develop basis functions which are smooth (rational) polynomials defined in terms of the Bézier extraction framework and which pass standard patch tests. We then develop a collocation procedure which correctly accounts for sharp edges and corners, extraordinary points, and T-junctions. This approach is applied to several three-dimensional problems, including a real-world T-spline model of a propeller. We believe this work clearly illustrates the power of combining new analysis-suitable computer aided design technologies with established analysis methodologies, in this case, the boundary element method. © 2012 Elsevier B.V.

A multipoint potential field method (MPPF) for path planning of autonomous underwater vehicles (AUV) in 3D space is presented in this paper. The algorithm is developed based on potential field method by incorporating a directed search method for sampling the potential field. In this approach, the analytical gradient of the total potential function is not computed, as it is not essentially required for moving the vehicle to the next position. Rather, a hemispherical region in the direction of motion around the AUV's bow is discretized into equiangular points with center as the current position. By determining the point at which the minimum potential exists, the vehicle can be moved towards that point in 3D space. This method is very simple and applicable for real-time implementation. The problem of local minima is also analyzed and found that the local minima in 2D space can be easily overcome with the MPPF. A simple strategy to avoid the local minima in 3D space is also proposed. The proposed method reduces the burden of fine-tuning the positive scaling factors of potential functions to avoid local minimum. The algorithm development and the simulation results are presented. � 2013 Springer-Verlag Berlin Heidelberg.

A new algorithm for fully automatic structured mesh generation is described. The algorithm is applicable equally to two-dimensional regions and three-dimensional surfaces and solids. The effectiveness of the algorithm is illustrated with several examples. Copyright ? 1996 Elsevier Science Ltd.

In this paper a theory of thin piezoelectric plates is obtained throigh a rational derivation from the three-dimensional linear theory of piezoelectricity. The coupling between the ekictric and mechanical fields is taken into account, leading to a consistent definition of the bending and stretching stiffnesses. In particular, it is shown that a piezoelectric plate has a different stretching stiffness when it is used as an actuator or as a sensor. The procedure used to derive the field equations governing the piezoelectric plate problem is based on the initial functions method, in conjunction with a rescaling of the applied loads. The field equations are then rewritten in a variational form, according to a generalized statement of the virtual work principle, in order to deduce the compatible boundary conditions. The theory established here is used to find closed-form expressions of the solutions of some technical problems, involving piezoelectric plates used as sensors or actuators.

This paper presents a three-dimensional photoelastic investigation of two- and four-pile caps for different depth—pile spacing ratios. For the analysis, the pile caps were idealized as rectangular blocks subjected to patches of loading at the column and pile locations. The individual stress components, their maximum values and locations were determined. Graphs showing the variations of important normal and shear stress components across depth, non-dimensionalized with the applied column stress, were given. On the basis of the results obtained it is concluded that the factors which are not hitherto considered in the design of pile caps have a significant bearing on the stress distribution.

An investigation to study the behaviour of reinforced concrete four-pile caps by three-dimensional nonlinear finite element analysis is presented. Four-pile caps having different reinforcement layouts were considered. Eight-noded isoparametric brick elements with incompatible modes and two-noded three-dimensional truss elements were used to model the concrete and steel, respectively, of the pile caps. The steel elements were assumed to lie on the edges of the brick elements. The smeared cracking model was employed for modelling cracks during the analysis. The nonlinear components, such as multiaxial compressive behaviour of concrete, including strain softening, cracking of concrete and yielding of steel reinforcement, were considered. The load deflection characteristics, the strains in the reinforcement, the crack patterns and the ultimate loads are presented herein. Some of the theoretical results are compared with those obtained from experiments carried out on reinforced concrete pile cap specimens. ? 1995.

Atherosclerosis is the third leading cause of morbidity and mortality in the Western world. Low and oscillating wall shear stress (WSS) regions have been previously reported as parameters that correlate with the development of atherosclerosis. In this study we investigated geometric and hemodynamic changes in the carotid bifurcation as a result of posture change. Data from magnetic resonance imaging (MRI) were used to construct three dimensional (3D) surface models and computational fluid dynamic (CFD) fields. Two healthy volunteers were imaged by MRI in three different head postures: a) the supine neutral (N) head position, b) the prone position with leftward head rotation (LR) up to 80° and c) the prone position with rightward head rotation (RR) up to 80°. The area exposure to unfavorable hemodynamics, based on thresholds set for oscillatory shear index (OSI), WSS and relative residence times (RRT), was used to quantify the hemodynamic impact on the wall. Significant change in the hemodynamic burden on the wall was found for the OSI. The velocity profile at the common carotid artery (CCA) upstream of the carotid bifurcation (CB) was investigated at the supine and RR prone position for six healthy volunteers. The results indicated that blood flow rate decreased at peak systole, for the prone position for both the right and left CCAs. © 2012 IEEE. 727 731 Sponsors: IEEE IEEE Computer Society University of Cyprus Biological and AI Foundation (BAIF) Frederick University Conference code: 95206

In forward osmosis (FO), an osmotic pressure gradient generated across a semi-permeable membrane is used to generate water transport from a dilute feed solution into a concentrated draw solution. This principle has shown great promise in the areas of water purification, wastewater treatment, seawater desalination and power generation. To ease optimization and increase understanding of membrane systems, it is desirable to have a comprehensive model that allows for easy investigation of all the major parameters in the separation process. Here we present experimental validation of a computational fluid dynamics (CFD) model developed to simulate FO experiments with asymmetric membranes. Simulations are compared with experimental results obtained from using two distinctly different complex three-dimensional membrane chambers. It is found that the CFD model accurately describes the solute separation process and water permeation through membranes under various flow conditions. It is furthermore demonstrated how the CFD model can be used to optimize membrane geometry in such as way as to promote the mass transfer. © 2012 by the authors; licensee MDPI, Basel, Switzerland.

The simulation of damaged honeycomb sandwich structures is an important aspect in the structural health monitoring and prognosis. This paper studies finite element modeling aspects of delaminated honeycomb sandwich structure. The models proposed are 3-D model of the honeycomb sandwich construction using isotropic shell elements and a layered shell element model, both with contact elements defined in between the delaminated skin and core. Case study is conducted on damaged and undamaged metallic sandwich beam with 3-D shell element modeling and layered element modelling. The models are validated using three point bending test of damaged and undamaged beams. Results are compared with the experimental, theoretical and finite element results. The results show that the layered element modeling simulates the stiffness and gives the similar results to that of 3D model in the global responses and is computationally efficient. � 2012. MechAero Foundation for Technical Research & Education Excellence.

Bu çalışma, 07-08 Mayıs 2010 tarihleri arasında Bursa[Türkiye]’da düzenlenen 5. Automotive Technology Conference (OTEKON)’da bildiri olarak sunulmuştur. A three-dimensional (3-D) transient numerical analysis was performed inside an automobile cabin during cooling period. A three-dimensional vehicle cabin including glazing surfaces was modelled by using the real dimensions of a car. A virtual manikin with real dimensions and physiological shape was added to the model of the vehicle cabin, and it was assumed that the manikin surfaces were subjected to constant temperature. The virtual manikin was divided into 17 parts in standing posture to evaluate the local heat transfer characteristics of the human body during transient cooling period. We considered three different cases that the cooling capacity of the automobile cabin was same for all cases. Three-dimensional fluid flow, temperature distribution and heat transfer characteristics inside the automobile cabin were calculated with different type of inlet vents. Comparisons of the numerical results were presented and discussed.

Institut de Radioprotection et de Sûreté Nucléaire (IRSN) performed a study relative to the thermal behaviour of a new TN International package design for transport of spent fuel assemblies called TNH112. The aim of this study is to evaluate the behaviour of the package exposed to fires, with durations and temperatures different from those required in the IAEA regulation TS-R-1 (respectively 30 min and 800°C). Its main objective is to provide quantitative data available for safety assessment in emergency situations involving fires. Moreover it can also be used for a cross comparison with the analysis of the thermal behaviour of the package during the IAEA regulatory fire test presented by the applicant in the package design safety analysis report. This study is based on numerical calculations performed with the code THERMX-PROTEE. The three-dimensional model used represents a quarter of the upper half of the package, where the closure system is located. The thermal behaviour of the neutron-shielding resin located in the cavity plug, the trunnions and the packaging body was modelled to allow simulation of endothermic reactions of vaporisation. During the heating phase of the fire test, the water vapour produced in the heated resin components is transferred and condensed in the nearby colder elements; the associated thermal transfers can rapidly increase the temperature of the colder elements. The part of the vapour which cannot be condensed when most of the nearby resin elements reach a temperature above 100°C is evacuated through the holes that are distributed throughout the external envelope of the packaging and closed by fusible plugs under normal conditions. A specific calculation module has been developed to take into account the corresponding energy transfers. This module was qualified by comparison with the results of experimental fire tests. The calculations performed in the framework of this study cover fire temperatures between 400 and 1000°C. One of the results of those calculations is the time necessary to reach the maximum allowable temperature of the elastomer gaskets. © W. S. Maney & Son Ltd 2012.

The study of the contact stresses generated when two surfaces are in contact plays a significant role in understanding the tribology of contact pairs. Most of the present contact models are based on the statistical treatment of the single asperity contact model. For a clear understanding about the elastic-plastic behavior of two rough surfaces in contact, comparative study involving the deterministic contact model, simplified multi-asperity contact model, and modified statistical model are undertaken. In deterministic contact model analysis, a three dimensional deformable rough surface pressed against a rigid flat surface is carried out using the finite element method in steps. A simplified multi-asperity contact model is developed using actual summit radii deduced from the rough surface, applying single asperity contact model results. The resultant contact parameters like contact load, contact area, and contact pressure are compared. The asperity interaction noticed in the deterministic contact model analysis leads to wide disparity in the results. Observing the elastic-plastic transition of the summits and the sharing of contact load and contact area among the summits, modifications are employed in single asperity statistical contact model approaches in the form of a correction factor arising from asperity interaction to reduce the variations. Consequently, the modified statistical contact model and simplified multi-asperity contact model based on actual summit radius results show improved agreement with the deterministic contact model results. � 2012 American Society of Mechanical Engineers.

In the present study, an aerothermodynamic analysis of high-speed flow fields through a divergent duct (similar to a supersonic combustor: hereafter referred to as supersonic combustor in the paper), without injection and with high enthalpy cross injection, has been performed. Initially, the thermal and flow analyses of the combustor are carried out by passing vitiated air at a temperature of 607.5 K, and this is followed by a computational analysis of the interaction of the flow field with the structure, when high enthalpy air is injected. The flow is turbulent in the combustor and the k-ω model has been considered to be appropriate for such cases, as it can resolve vorticity and highly strained flows. The study also emphasizes on the advantages of two-dimensional modelling over three dimensional modelling for cold flow cases in supersonic combustors, which could serve as an alternative, for wind tunnel tests as well as computationally expensive three dimensional numerical analysis. A comparison of various turbulence models for supersonic flows without cross injection has been carried out to arrive at the suitable model. For the cases of cross/transverse injection, the Mach numbers considered for investigation are 2, 2.5 and 3. The pressure, temperature and heat flux predictions for the cases with and without injection compare well with the experimental results.

The vibration and damping analysis of orthotropic cylindrical shells with a constrained viscoelastic core is carried out by using a finite element based on a discrete layer theory. The material damping of the facings is also included in the analysis. Results are represented for different geometric and material properties of the shell. The data and trends presented for various cases could be useful for designers in choosing damping treatments for composite shells. ? 1994 Academic Press. All rights reserved.

Milling of thin-walled aerospace structures is a critical and challenging process. Available models for the prediction of the effect of the fixture on the dynamic response of flexible workpieces are computationally demanding and fail to represent practical cases for milling of thin-walled structures. Based on the analysis of typical structural components encountered in the aerospace industry, a generalized unit-element, with the shape of an asymmetric pocket, was identified to represent the dynamic response of these components. Accordingly, a computationally efficient dynamic model was developed to predict the dynamic response of typical thin-walled aerospace structures using the Rayleigh-Ritz method. In the formulation of this model, the dynamics of a 3D pocket is represented by an equivalent 2D multispan plate taking into account the effect of deformable fixture supports. The developed model was validated numerically and experimentally for different workpiece geometries and various types of loading. This model resulted in one to two orders of magnitude reduction in computation time when compared with the finite element models, with prediction errors less than 10%. The developed model meets the conflicting requirements of prediction accuracy and computational efficiency needed for interactive fixture design. © 2011 American Society of Mechanical Engineers.

In this paper, a meso-scale repeated unit cell model for a general [±θ]n angle-ply laminate is developed and the implementation of periodic boundary conditions in a finite element analysis for this 3-D model is presented. A nonlinear viscoelastic constitutive model and a post-damage constitutive model based on the concept of a smeared crack are also incorporated in the finite element analysis. The stress-strain response and the damage initiation and propagation for different values of θ are predicted. © 2011 Published by Elsevier Ltd., 11th International Conference on the Mechanical Behavior of Materials, ICM11, 5 June 2011 through 9 June 2011, Como

PurposeThe purpose of this paper is to present in‐depth numerical modelling of heat and mass exchange in industrial induction channel furnace (ICF).Design/methodology/approachThe turbulent heat and mass exchange in the melt is calculated using a three‐dimensional (3D) electromagnetic model and a 3D transient large eddy simulation method. The simulation model has been verified by flow velocity and temperature measurements, which were carried out using an industrial sized channel inductor operating with Wood's metal as a low temperature model melt.FindingsThe ICF is well‐established for melting, holding and casting in the metallurgical industry. But there are still open questions regarding the heat and mass exchange in the inductor channel itself and between the channel and the melt bath. Different new designed channel geometries have been investigated numerically in order to find an optimized shape of the channel, which leads to an improved heat and mass transfer.Originality/valueLong‐term computations for the industrial ICF have been performed. Low frequency oscillations of the temperature maximum and its position in the ICF channel are considered.

The stellarator Wendelstein 7-X (W7-X) is presently under construction at the Max-Planck-Institut für Plasmaphysik in Greifswald, Germany. The plasma density profile will be measured by two-colour interferometry where for each line of sight through the plasma the phase shifts of two far-infrared laser beams are compared. Due to the 3D shape of the superconducting coils in W7-X, opposite ports are not available. Instead, corner cube retro-reflectors (CCR) will be incorporated in the plasma vessel heat shield that reflect the beams back to the entrance window and diagnostic. This requires high accuracy of the reflecting surfaces which will be subjected to thermal loads from plasma radiation and therefore be heated up, displaced and deformed during operation. ANSYS is used to perform coupled thermo-mechanical analyses of the CCR, including plasma radiation, thermal conduction, and radiation between all parts. The resulting displacements provide the inputs to MATLAB routines which then yield local deformations, curvature radii, and tilting of the reflecting surfaces. This information is used to optimize the design of the CCR and their fixations. © 2011 Elsevier B.V. All Rights Reserved.

The aim of this study was to quantify strain partitioning in HSLA-65 joints, welded with three types of weld filler: 6011 undermatched weld filler, 7018 matched weld filler, and 9016 overmatched weld filler. Strain measurements were made using a three-dimensional digital image correlation system while specimens were tested on a displacement controlled servo-hydraulic test frame. Crosshead displacement rates ranged from 0.056 mm/s to almost 56 mm/s. Coupons were cut from flux-core arc welded HSLA-65 plates to characterize the base metal, weld filler materials, and mismatched welds. Constitutive material properties could be extracted reliably for all coupons at the lowest displacement rate and showed that, as expected, all weld fillers had similar elastic modulus values but different yield strengths. A comparison of the peak strains at 85 per cent of maximum elongation showed that overall the failure strain was inversely related to the crosshead displacement rate. Analysis of the mismatched coupons found that the failure location was a function of weld filler and was independent of strain rate. Higher magnification imaging of the weld nugget showed that strain partitioning occurred within the weld zone, with slightly lower strains in the cap pass as opposed to the root pass.

Two different approaches that explicitly incorporate the stress triaxiality into cohesive zone models applicable to thin-walled structures are compared to identify the relative merits and limitation of these models. The number of model parameters involved, the ease of parameter determination and the predictive capabilities of the models over a wide range of thin-walled geometries are investigated. The first model, proposed recently by the authors, uses basic elastic-plastic constitutive equations combined with a model parameter depending on the average triaxiality in plane stress conditions. The second model incorporates stress-state through exponential dependence of cohesive strength on triaxiality, similar to plane strain studies earlier. The respective parameters for both models are identified and subsequently applied to several notched and precracked specimens. It is shown that in contrast to stress-state independent models, both constraint dependent models are able to predict well failure of a wide range of structures. While the model incorporating triaxiality dependent cohesive parameters has more parameters to be determined, it is not restricted to any specific stress condition and therefore can be extended to arbitrary three-dimensional stress-states. � 2010 Elsevier Ltd.

Friction stir welding is a patented joining process invented in 1991 at The Welding Institute in Cambridge, UK, and further developed to the stage suitable for production. In this process, a wear resistant rotating tool is used to join sheet and plate with different materials such as aluminum, copper, lead, magnesium, zinc, and titanium. This work studies the thermal characteristics of this process and provides a modeling technique based on Neural Network that can be used for real-time control. A thermal feed-back control method is presented to control the process. Using some thermal modeling for the heat distribution during friction stir welding process, this paper displays the complexity of obtaining an accurate design for the thermal feed back control. A three-dimensional transient heat transfer model is developed here for a sequential joining process (Friction Stir Welding- FSW) applied on aluminum parts. A neural network is created based on a set of experiments to predict the spatial and temporal variations in the temperature over the weld seam for different set of input variables. The model includes the dynamic and friction behavior of the rotating spindle and the thermal behaviors of the weld components involved. The significance of this modeling approach is that it captures the movement of the spindle, simulating a sequential joining process along a continuous weld seam. The modeling results are compared with experimental data obtained by thermocouples and infrared camera, and accurately predict the trend of variations in weld temperature. A fuzzy-logic based controller is proposed to regulate the FSW process parameters to maintain the weld temperature within the margin required to ensure the weld quality. This modeling and control system can have applications in manufacturing aluminum parts in automotive and aerospace industry. Copyright © 2011 by ASME., ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC/CIE 2011, 28 August 2011 through 31 August 2011, Washington, DC