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This paper presents a detailed test procedure, including the test facilities, the design of the ship model and the releasing mechanism of the damaged opening. The aim is to analyze the effects of air compressibility on the flooding process and motion responses of the damaged ship. To assist in the explanation of the test results, necessary numerical simulations are performed. Through carrying out series of model tests, it was found that the limited ventilation level not only delays the flooding process but also affects the dynamic responses of the damaged ship. In addition, the test results verify the assumption of 10% full ventilation publihsed by the International Maritime Organization (IMO) while analyzing the applicability of this assumption to the single flooding compartment. The results also show that ensuring a proper ventilation level in the flooding compartments can mitigate gas-liquid interactions and thus improve the dynamic response of the damaged ship. Based on the research results in this paper, an 8% ventilation ratio can be preliminarily used as a reference standard for similarventilation designs. Finally, the obtained experimental data in this paper can be used as a benchmark for future reliability analysis of the numerical methods. • This paper presents a detailed flooding test procedure, including the test facilities, the design of the ship model and the releasing mechanism of the damaged opening. • Test results verify the assumption of 10% full ventilation in IMO while analyzing the applicability of this assumption to the single flooding compartment. • The experimental data can be used as a benchmark for future reliability analysis of numerical methods. [ABSTRACT FROM AUTHOR]

Summary: The paper describes and evaluates an incremental plasticity constitutive model for unsaturated, anisotropic, nonexpansive soils (CMUA). It is based on the modified Cam‐Clay (MCC) model for saturated soils and enhances it by introducing anisotropy (via rotation of the MCC yield surface) and an unsaturated compressibility framework describing a double dependence of compressibility on suction and on the degree of saturation of macroporosity. As the anisotropic and unsaturated features can be activated independently, the model is downwards compatible with the MCC model. The CMUA model can simulate effectively: the dependence of compressibility on the level of developed anisotropy, uniqueness of critical state independent of the initial anisotropy, an evolving compressibility during constant suction compression, and a maximum of collapse. The model uses Bishop's average skeleton stress as its first constitutive variable, favouring its numerical implementation in commercial numerical analysis codes (eg, finite element codes) and a unified treatment of saturated and unsaturated material states. [ABSTRACT FROM AUTHOR]

As is well known, approximate integral equations for liquids, such as the hypernetted chain (HNC) and Percus–Yevick (PY) theories, are in general thermodynamically inconsistent in the sense that the macroscopic properties obtained from the spatial correlation functions depend on the route followed. In particular, the values of the fourth virial coefficient B4 predicted by the HNC and PY approximations via the virial route differ from those obtained via the compressibility route. Despite this, it is shown in this paper that the value of B4 obtained from the virial route in the HNC theory is exactly three halves the value obtained from the compressibility route in the PY theory, irrespective of the interaction potential (whether isotropic or not), the number of components, and the dimensionality of the system. This simple relationship is confirmed in one-component systems by analytical results for the one-dimensional penetrable-square-well model and the three-dimensional penetrable-sphere model, as well as by numerical results for the one-dimensional Lennard-Jones model, the one-dimensional Gaussian core model, and the three-dimensional square-well model. [ABSTRACT FROM AUTHOR]

Abstract This paper discusses the behavior of sand-rubber particle mixtures under one-dimensional compression tests. First, experimental results on ideally prepared sand-rubber particle mixtures with different rubber contents are discussed. Then, novel simulations using the Discrete Element Method are presented. The grain-scale deformability of the rubber particles is considered using a bonded particle model. The model is calibrated based on the experimental results of pure sand and pure rubber and it is further validated for all intermediate rubber contents. The numerical model is able to accurately predict the compressive behavior of the mixtures as well as the residual strain. [ABSTRACT FROM AUTHOR]

Abstract Use of geotextile-encased sand columns (GESC) to improve weak soils is an emerging technology that has great promise for field applications. This paper contains the results of a numerical study with the goal of quantifying the benefits of geotextile encasement under different conditions. A three-dimensional finite difference method implemented in FLAC3D 5.01 was used to evaluate the performance of a vertically loaded individual GESC installed in loose sand. The numerical model was first verified using the results of experimental tests performed on 150-mm diameter GESC installed in loose sand. The influence of various parameters was investigated in this study, including GESC diameter and length, soil thickness, geotextile encasement length, geotextile stiffness, and friction angle and dilation angle of the infill material. The results of the numerical model showed that vertically loaded GESC of smaller diameter experienced less settlement and lateral expansion than those of larger diameter. The geotextile material with higher stiffness had a substantial influence on the performance of GESC. The maximum effective geotextile encasement length depended on the load on the column head or the compressibility of the column. [ABSTRACT FROM AUTHOR]

This paper presents a numerical simulation using PLAXIS code of geosynthetic reinforced embankment over locally weak zones. The case study concerns the reinforcement of the road embankment which crosses a section of about 11 km on sabkha soil of Chott El Hodna in Algeria. This salt flat is dry in summer but gets flooded in winter. The site observations and the geotechnical investigations indicated that the soil of this sabkha is characterised by high compressibility, low bearing capacity and contains locally weak zones of limited extent. The main objective of this paper is to assess the effect of geosynthetic reinforcement on the settlement of the embankment over locally weak zone. The influence of some parameters, namely the compressibility parameter of locally weak zone, the stiffness of geosynthetic, the locally weak zone geometry and the friction angle of embankment fill is also analysed. The results show that the computation with large displacement is more suitable than small displacement for this problem and the differential settlement improvement is due to the combination of the membrane strength effect of the geosynthetic and the arching effect within the embankment fill. [ABSTRACT FROM AUTHOR]

This paper presents a three-dimensional numerical model of swirled compressible flow in the Ranque–Hilsch vortex tube. We proposed the modification of the energy conservation equation used in Reynolds Averaged Navier–Stokes (RANS) numerical simulations. While the additional turbulent heat transfer mechanism caused by gas compressibility is taken into account in the proposed equation, it is not applied in standard RANS models. The data were obtained both by standard and proposed energy conservation equations using the k − ε turbulence model. The application of the proposed energy conservation equation was shown to increase the accuracy of static and total temperature distribution prediction. The objective of this paper is the demonstration of the applicability of the new numerical model based on the proposed energy conservation equation after the calibration of empirical coefficients. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents a new interpretation method for pulse tests, a field permeability test that allows for rapid measurements of hydraulic conductivity k in aquitards. This new method applies to soft clay deposits. To initiate a pulse test, a known volume of water is injected into the sand filter of a monitoring well isolated by a packer. The resulting pressure increase yields an outward movement of the sand filter cavity wall. After presenting the usual interpretation methods and their limits, this paper proposes a new interpretation method based on a coupled analysis of the pressure and displacement fields in the soil using the Biot-Darcy formulation. A series of analytical and numerical non-dimensional velocity graphs, normalized plots of the mean hydraulic head difference versus its rate of change, are given. For a linear elastic material, these type curves show relatively small variations with the sand filter aspect ratio and the Poisson ratio of the tested clay. The type curves are also found to be independent of the clay compressibility ( mv) and k, an important result. A series of pulse tests conducted in a soft marine clay deposit near Montreal, Canada, are interpreted with the proposed method. The hydraulic conductivity values calculated from these tests are closely correlated with independent estimates obtained using long-duration variable-head tests. Compared with previous interpretation methods, the proposed method allows soil volume changes to be reconciled with cavity expansion phenomena and the range of type curves available for the interpretation of test data to be constrained. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Lengthy retaining walls are typically required in several geotechnical applications. Compacted soil is the classic backfill behind such walls, yet soil has a high unit weight that imposes large lateral loads and may lead to outsized wall dimensions. Geofoam or foam made of expanded polystyrene (EPS) can substitute the soil backfill due to its light weight and high compressibility and can reduce the lateral static loads imposed on walls. In this paper, EPS mechanical properties were measured in addition to the interface friction between this geomaterial and other materials, such as sand and concrete. A reliability analysis was conducted to develop the partial resistance factors required for the main EPS properties. Using a three-dimensional (3D) numerical analysis, the reliable EPS properties were used in the hardening soil constitutive model to simulate flexible walls with EPS inclusions of various thicknesses. Analysis outcomes were verified against measurements from a physical prototype and were also compared with results from the literature. From the main outcomes, the lateral pressure on flexible walls can be significantly reduced by up to 25% using a relatively thin EPS inclusion, and design charts for the reduction in the lateral pressure are provided. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the role played by the material compressibility in the oscillatory behaviour of hyperelastic spherical shells subjected to dynamic inflation. For that purpose, we carried out a comprehensive nondimensional numerical analysis using: (i) a finite differences MacCormack's scheme implemented in MATLAB, and (ii) a finite element model developed in ABAQUS/Explicit (Abaqus Explicit v6.10 user's manual, version 6.10 edn. ABAQUS Inc., Richmond, 2010). We have detected that numerical dispersion and diffusion impose limits to the capacity of the computations to describe the shock wave that emanates from the inner surface of the shell due to the application of the inflation pressure. Nevertheless, both numerical approaches capture the essential features that describe the oscillatory behaviour of the shell, including the maximum stretch of the oscillation. Using the key nondimensional groups that control the problem at hand, we have conducted a parametric study to assess the role played by nondimensional applied pressure, material compressibility, and nondimensional shell thickness in the oscillatory behaviour of the specimen. We have shown the interplay between the maximum amplitude of the oscillation and the applied pressure and obtained the critical pressure for which the oscillatory behaviour is lost, leading to an unbounded expansion of the spherical shell. Moreover, our calculations have revealed that the wave propagation within the specimen plays a key role in the dynamic response of the shell. The phase portraits used to represent the oscillatory behaviour of the spherical shell show a characteristic sawtooth form that is accentuated with the increase in material compressibility and shell thickness. [ABSTRACT FROM AUTHOR]

In this paper an inverse problem is considered for a non-coercive partial differential equation, issued from a mass conservation cavitation model for a slightly compressible fluid. The cavitation phenomenon and compressibility take place and are described by the Elrod model. The existence of an optimal solution is proven. Optimality conditions are derived and some numerical results are given. [ABSTRACT FROM AUTHOR]

A bubble jet with velocity of hundred meters per second forms at the final stage of bubble collapse, which makes the compressibility of flow field can’t ignore. Based on the spherical bubble model of Geers and Hunter, a compressible numerical model is improved for simulating non-spherical bubble dynamic in this paper. In the present implementation, the compressibility of external liquid and the wave effect of internal gas are considered by the first order external doubly asymptotic approximation and the first order internal doubly asymptotic approximation, respectively. In addition, the volume acceleration model is applied to calculate the initial condition of bubble. After that, the improved compressible numerical model is validated against the underwater explosion experiment data. The numerical result of bubble radius correlates well with the experiment data. Finally, based on the improved compressible numerical model, the influences of wave effect of internal gas and initial condition of bubble on bubble dynamics in free field and gravity field are investigated. The wave effect of internal gas makes bubble radius, radial velocity, translational displacement, jet velocity and remaining total energy decrease. The initial radial velocity, on the one hand, makes bubble radius, radial velocity, translational displacement, jet velocity and remaining total energy increase at the first bubble cycle; on the other hand, intensifies bubble radius, radial velocity, translational displacement, jet velocity and remaining total energy decay. [ABSTRACT FROM AUTHOR]

Abstract: This work concerns the simulation of compressible multi-material fluid flows and follows the method FVCF-NIP described in the former paper (Braeunig et al., 2009 ). This cell-centered finite volume method is totally Eulerian since the mesh is not moving and a sharp interface, separating two materials, evolves through the grid. A sliding boundary condition is enforced at the interface, and mass, momentum and total energy are conserved. Although this former method performs well on 1D test cases, the interface reconstruction suffers of poor accuracy in conserving shapes for instance in linear advection. This situation leads to spurious instabilities of the interface. The Enhanced-NIP method presented in the present paper provides a solution to an inconsistency in the former NIP method. This solution strikingly improves the numerical results. It takes advantage of a more consistent description of the interface in the numerical scheme. Results for linear advection and compressible Euler equations for inviscid fluids are presented to assess the benefits of this new method. [Copyright &y& Elsevier]

Abstract: This paper develops a theoretical solution for the problem of determining thin wing''s lift force while moving near flat surface (a screen). The solution is determined under the assumption of fluid being ideal and incompressible. The Chaplygin–Zhukovsky hypothesis of rear-edge-limited solution is taken into consideration. The solution of a problem is reduced to the Fredholm equation that is solved numerically. The generalization of the Zhukovski solution was obtained, which provides the lift force dependence on the altitude of the flight. The behavior of the lift force is very peculiar: it increases on decreasing altitude above the rigid surface. The screen effect becomes essential on moving wing altitude being smaller than the wing''s length. The effect was detected experimentally before and gave birth to construction of a special flying vehicle named “ecranoplan”. It is shown in the paper that the lift force could increase several orders of magnitude. This effect could be used in developing flying vehicles of high loading capacity, which could be used in the territories of smooth surface: savannas, steppes, deserts, lakes, swamps, etc. The effect could be used for developing vehicles for operation on other planets having not very dense atmosphere and relatively smooth surface (like Mars). Flights in such an atmosphere are energy consuming, while using the effect of lift force increase near the surface could be very effective. [Copyright &y& Elsevier]

Abstract: In this paper, the effects of the nozzles number on the flow and power of cooling of a vortex tube are studied, using a three-dimensional numerical fluid dynamic model. Vortex tube has interesting functions and several industrial applications, and, as a refrigerator, it is used as a spot cooling device in industry. High-pressure compressible fluid enters the vortex tube and leaves its cold and hot outlets at lower and higher temperatures than that of the inlet flow, respectively. A few experimental and a fewer numerical studies have been conducted in recent years on the effects of nozzles number of a vortex tube. However, in this paper, the effects of nozzles number on the flow and power of cooling of a counter-flow vortex tube are investigated comprehensively. It is observed that as the number of nozzles is increased, power of cooling increases significantly while cold outlet temperature decreases moderately. [Copyright &y& Elsevier]

Abstract: This paper presents the development and illustrates the application of semi-analytical solutions for plastic buckling (bifurcation) problems involving perfectly straight and uniformly compressed thin-walled metal members. These solutions are derived on the basis of a non-linear Generalised Beam Theory (GBT) formulation, recently proposed by two of the authors, that resorts to a linearised buckling analysis that adopts Hill’s hypo-elastic comparison solid method to obtain the plastic bifurcation loads and associated buckling mode shapes. Moreover, both small-strain incremental and deformation plasticity theories are employed. Several numerical illustrative examples are presented and discussed throughout the paper and closed-form analytical formulae are also derived. The accuracy of the GBT-based semi-analytical plastic bifurcation predictions is assessed through the comparison with (i) available theoretical solutions and/or (ii) results yielded by a special shell finite element model developed by one of the authors. [Copyright &y& Elsevier]

In this paper, numerical investigation of airflow through a human upper airway is presented using an unstructured-based characteristic-based split (CBS) scheme. The CBS scheme used in the present study employs a fully explicit matrix-free solution procedure along with artificial compressibility. A one equation Spalrat–Allmaras (SA) turbulence model is employed to study low and moderate Reynolds number flows. A detailed discussion of the qualitative and quantitative results is presented. The results show a strong influence of the Reynolds number on the flow pattern and quantities of interest, pressure drop and wall shear stress. It is also apparent that SA model can be employed on unstructured meshes to predict the steady flow with good accuracy. Thus, the novelties of the present paper are: use of the unstructured mesh-based solution algorithm and the successful application of the SA model to a typical human upper airway. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of B-spline surface interpolation to serial contours, where the number of points varies from contour to contour. A traditional approach to the problem creates a set of B-spline curves via B-spline curve interpolation to each contour, makes them compatible via degree elevation and knot insertion and performs B-spline surface lofting to get a B-spline surface that interpolates them. The approach tends to result in an astonishing number of control points in the lofted B-spline surface. This situation arises mainly from the inevitable process of progressively merging different knot vectors to make the B-spline curves compatible. This paper presents a new approach for fixing this problem. The approach includes a novel process of obtaining a set of compatible B-spline curves from the given contours. The process is based on universal parameterisation [1, 2], allowing the knots to be selected freely but leading to a more stable linear system for B-spline curve interpolation. Since the number of control points in each compatible B-spline curve is equal to the highest number of contour points, the proposed approach can realise efficient data reduction and provide a compact representation of a lofted B-spline surface while keeping the desired surface shape. Some experimental results demonstrate its usefulness and quality. [ABSTRACT FROM AUTHOR]

A theoretical formalism to investigate the elastic anisotropy and phonon focusing for tetragonal crystals is described in detail in this paper. This is applied for γ-TiAl and both of the numerical indicators and the three dimensional images of elastic anisotropy are derived. The percentage of bulk and shear anisotropies indicate γ-TiAl exhibits relatively high degree of anisotropy in shear but small anisotropy in compressibility. Anisotropy indexes A ∗ and A U demonstrate γ-TiAl possesses high degree of anisotropy, and this feature is also reflected in the three dimensional Young’s modulus, shear modulus and Poisson’s ratio. Three slowness surfaces are constructed for γ-TiAl to investigate the phonon focusing patterns, and the group velocity surfaces are also obtained to gain more insight into the elastic anisotropy. Due to elastic anisotropy, both of the slowness surfaces and the group velocity surfaces are nonspherical. The anisotropy is highest for slow transverse mode, and then followed by fast transverse mode and longitudinal mode. Interestingly, only transverse phonons cause caustics for γ-TiAl. Furthermore, the phase velocity and group velocity are not collinear for transverse mode in some directions, resulting in cuspidal edges along these directions in the group velocity surfaces. [ABSTRACT FROM AUTHOR]

Abstract: The buckling and postbuckling responses of cylindrical sandwich panels, subjected to non-uniform in-plane loadings are investigates in this paper by analytical method. A fourth and fifth order expansions are used respectively for the transverse and tangential displacement of the core to model the core compressibility effect. The stress distribution within the panels due to the applied non-uniform in-plane edge loadings are determined by prebuckling analysis. The governing partial differential equations describing the buckling and postbuckling behavior of cylindrical sandwich panels are derived using the principle of minimum total potential energy. Galerkin’s method is used to reduce the governing partial differential equations to a set of non-linear algebraic equations. Newton–Raphson method in conjunction with Riks approach is employed to solve the algebraic equations. Numerical results are presented for both flat and cylindrical sandwich panels subjected to various non-uniform in-plane edge loadings. The sandwich panels used in the present investigation are made up of isotropic and composite materials. [Copyright &y& Elsevier]

Abstract: In this paper, we develop a “modified” immersed finite element method (mIFEM), a non-boundary-fitted numerical technique, to study fluid–structure interactions. Using this method, we can more precisely capture the solid dynamics by solving the solid governing equation instead of imposing it based on the fluid velocity field as in the original immersed finite element (IFEM). Using the IFEM may lead to severe solid mesh distortion because the solid deformation is been over-estimated, especially for high Reynolds number flows. In the mIFEM, the solid dynamics is solved using appropriate boundary conditions generated from the surrounding fluid, therefore produces more accurate and realistic coupled solutions. We show several 2-D and 3-D testing cases where the mIFEM has a noticeable advantage in handling complicated fluid–structure interactions when the solid behavior dominates the fluid flow. [Copyright &y& Elsevier]

Use of Terzaghi's one-dimensional consolidation theory is not suitable for consolidation of highly deformable soft clays such as dredged soils. To model this condition, it is necessary to consider non-linear finite strain consolidation behavior, i.e., changes in compressibility and permeability with increasing stress. A one-dimensional non-linear finite strain numerical model, Primary Consolidation, Secondary Compression, and Desiccation of Dredged Fill (PSDDF), has been used to predict the stress-dependent settlement of fine-grained dredged materials. In this paper, two case studies of using PSDDF are discussed to illustrate the applicability and accuracy of PSDDF. The first case study involves PSDDF simulations of laboratory-phased placement of a marine clay dredged from Busan, Korea. PSDDF results are in good agreement with the corresponding results of the laboratory large strain consolidation tests. The other involves estimating the service life of the Craney Island Dredged Material Management Area near Norfolk, Virginia, in the United States. The excellent agreement between measured and calculated values shows that PSDDF is a reliable tool for predicting settlement of dredged material. [ABSTRACT FROM PUBLISHER]

Abstract: In this work, fully explicit numerical solutions for axial flow convection in cylindrical domains, completely or partially filled with a fluid saturated porous medium, are presented. Laminar natural convection in a vertical porous annulus and in a vertical annulus with a centrally located heat generating solid or porous rod, and laminar forced convection in a pipe partially filled with a porous medium are numerically simulated. Novel stability conditions are carried out for the axisymmetric version of the Artificial Compressibility (AC) Characteristic Based Split (CBS) algorithm, based on finite elements, in order to effectively solve the above problems. The results presented in this paper are validated against experimental and numerical data available from the literature. The problem taking into account the presence of the porous rod in the vertical annulus has been presented here for the first time. [Copyright &y& Elsevier]

Abstract: Phospholipidic membranes and vesicles constitute a basic element in real biological functions. Vesicles are viewed as a model system to mimic basic viscoelastic behaviors of some cells, like red blood cells. Phase field and level-set models are powerful tools to tackle dynamics of membranes and their coupling to the flow. These two methods are somewhat similar, but to date no bridge between them has been made. This is a first focus of this paper, where we show how the phase-field methods developed in Biben and Misbah (2003) , Beaucourt (2004) , Biben (2005) for immersed vesicles could be considered as a level-set method for a particular strain–stress relationship. The main conclusion is that the two methods share several common features and we shall provide the correspondence between the two methods. Furthermore, a constitutive viscoelastic law is derived for the composite fluid: the ambient fluid and the membranes. We present two different approaches to deal with the membrane local incompressibility, and point out differences. Some numerical results following from the level-set approach are presented. [Copyright &y& Elsevier]

Abstract: The aim of this paper is the numerical simulation of compressible hydrodynamic strong implosions, which take place for instance in Inertial Confinement Fusion. It focuses in particular on two crucial issues, for such calculations: very low CFL number at the implosion center and approximation error on the initial geometry. Thus, we propose an exceptional points method, which is translation invariant and suitable to curved meshes. This method is designed for cell-centered Lagrangian schemes (GLACE , EUCCLHYD ). Several numerical examples on significant test cases are presented to show the relevance of our approach. [Copyright &y& Elsevier]

Mesh-free particle (Lagrangian) methods have been used in a wide variety of applications in fluids studies in recent decades. A big advantage of these methods is the ability to model the deformations and spray generation in boundaries and interfaces, which are common problems with jets and jumps and may be difficult using Eulerian methods. Weakly compressible moving particle semi-implicit method (WC-MPS) has been developed and is used in this paper. The model is first validated for jet simulation and then applied to submerged hydraulic jumps. The flow regime, velocity distribution, and turbulence shear stresses at different distances from the jet inlet are investigated and compared with the analytical solution and experimental data. With this method, the inlet flow particles entering the domain can be tracked, as well as the development of vortices and recirculation in the corresponding turbulent flow fields. The comparison of MPS results with experimental data for submerged hydraulic jumps shows the using of WC-MPS reveals the flow characteristics especially in the critical circulating transition region of the jump. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with a new solid–fluid coupling algorithm between a rigid body and an unsteady compressible fluid flow, using an Embedded Boundary method. The coupling with a rigid body is a first step towards the coupling with a Discrete Element method. The flow is computed using a finite volume approach on a Cartesian grid. The expression of numerical fluxes does not affect the general coupling algorithm and we use a one-step high-order scheme proposed by Daru and Tenaud [V. Daru, C. Tenaud, J. Comput. Phys. (2004)]. The Embedded Boundary method is used to integrate the presence of a solid boundary in the fluid. The coupling algorithm is totally explicit and ensures exact mass conservation and a balance of momentum and energy between the fluid and the solid. It is shown that the scheme preserves uniform movement of both fluid and solid and introduces no numerical boundary roughness. The efficiency of the method is demonstrated on challenging one- and two-dimensional benchmarks. [Copyright &y& Elsevier]

Abstract: In this paper we address the numerical approximation of the incompressible Navier–Stokes equations in a moving domain by the spectral element method and high order time integrators. We present the Arbitrary Lagrangian Eulerian (ALE) formulation of the incompressible Navier–Stokes equations and propose a numerical method based on the following kernels: a Lagrange basis associated with Fekete points in the spectral element method context, BDF time integrators, an ALE map of high degree, and an algebraic linear solver. In particular, the high degree ALE map is appropriate to deal with a computational domain whose boundary is described with curved elements. Finally, we apply the proposed strategy to a test case. [Copyright &y& Elsevier]

Abstract: This paper is concerned with numerical predictions of relationship between operating speed and shaft power output of Stirling engines. Temperature variations in expansion and compression spaces as well as the shaft power output corresponding to different operating speeds were investigated by using a lumped-mass transient model. Effects of major operating parameters on power output were studied. Results show that as the operating speed increased, temperature difference between the expansion and compression spaces was reduced and as a result, the shaft work output decreased. However, the shaft power output is determined in terms of the shaft work output and the operating speed. When the operating speed was elevated, the shaft power output reached a maximum at a critical operating speed. Over the critical operating speed, the shaft power output decreased in high-speed regime. In addition, as air mass was reduced, either a decrease in thermal resistances or an increase in effectivenesses of the regenerator leads to an increase in the engine power. [Copyright &y& Elsevier]

Abstract: We have studied numerically the time development of the energy spectrum of inviscid, incompressible, helical flows. It is well known that helicity delays the development of turbulence. The aim of this paper is to study this phenomenon in more detail by investigating the influence of the number of modes in the initial flow field on the spectral development. We studied the cases with one, two, three or twenty-four modes with and without helicity in the initial flow field. It is found that the delay in the spectral development due to helicity is strongly dependent on the number of initial modes. The delay increases with decreasing number of modes. For the case of one initial mode with maximum helicity no development of the energy spectrum occurs. However, for the case of twenty-four initial modes with maximum helicity, energy transfer between the modes takes place without much delay when compared to the case of twenty-four initial modes without helicity. [Copyright &y& Elsevier]

Abstract: A three dimensional (3D) hybrid method combining the classical finite element (FE) method with the semi-analytical finite element (SAFE) technique is developed. This hybrid method is employed to study the interaction of guided waves with non-axisymmetric damages in cylinders. The near field surrounding the damage is analysed with the 3D FE method. The solution is expanded into sums of guided modes on both inlet and outlet cross-sections. Such eigenmode expansions enable separation into ingoing and outgoing waves, i.e., incident, reflected and transmitted waves. Using the SAFE method, elastic guided modes are then computed at the aforementioned cross-sections thus reducing the analysis to two dimensions (2D). The amplitudes of the incident modes are imposed, whereas those of the scattered modes are determined by solving the global system of the 3D hybrid FE-SAFE model. In this paper, a formula is proposed for the calculation of eigenforces and modal power flows from eigendisplacements and SAFE matrices. This has the advantage of simplifying the post-process of load eigenvectors in hybrid FE-SAFE methods. Results obtained for a vertical free-end cylinder are in good agreement with those published in the literature. Moreover, first results of the interaction of the fundamental compressional, flexural and torsional Pochhammer–Chree modes with non-axisymmetric vertical cracks are obtained and discussed. Then, the interactions of the fundamental compressional mode with oblique free-ends and cracks are briefly addressed. The power balance is shown to be satisfied with a good accuracy. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a 3D geometric modelling of a twin helical spring and its finite element analysis to study the spring mechanical behaviour under tensile axial loading. The spiralled shape graphic design is achieved through the use of Computer Aided Design (CAD) tools, of which a finite element model is generated. Thus, a 3D 18-dof pentaedric elements are employed to discretise the complex “wired-shape” of the spring, allowing the analysis of the mechanical response of the twin spiralled helical spring under an axial load. The study provides a clear match between the evolution of the theoretical and the numerical tensile and compression normal stresses, being of sinusoidal behaviour. The overall equivalent stress isovalues increases radially from 0° to 180°, being maximal on the internal radial zone at the section 180°. On the other hand, the minimum stress level is located in the centre of the filament cross section. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we propose a steady-state lattice Boltzmann equation which is independent of time for steady incompressible flows. On the basis of the steady-state lattice Boltzmann equation, we find a way of modeling some steady-state problems using the lattice Boltzmann model. In further study, we investigate steady-state incompressible flows with the method of the higher-order moment of equilibrium distribution functions and a series of partial differential equations for different space scales. By assuming , we obtain the momentum equation for incompressible steady-state flow. The numerical results show that the new method is effective. [Copyright &y& Elsevier]

Abstract: The paper extends weighted essentially non-oscillatory (WENO) methods to three dimensional mixed-element unstructured meshes, comprising tetrahedral, hexahedral, prismatic and pyramidal elements. Numerical results illustrate the convergence rates and non-oscillatory properties of the schemes for various smooth and discontinuous solutions test cases and the compressible Euler equations on various types of grids. Schemes of up to fifth order of spatial accuracy are considered. [ABSTRACT FROM AUTHOR]

Abstract: A study of the hydromagnetic flow due to a stretching sheet and heat transfer in an incompressible micropolar liquid is made. Temperature-dependent thermal conductivity and a non-uniform heat source/sink render the problem analytically intractable and hence a numerical study is made using the shooting method based on Runge–Kutta and Newton–Raphson methods. The two problems of horizontal and vertical stretching are considered to implement the numerical method. The former problem involves one-way coupling between linear momentum and heat transport equations and the latter involves two-way coupling. Further, both the problems involve two-way coupling between the non-linear equations of conservation of linear and angular momentums. A similarity transformation arrived at for the problem using the Lie group method facilitates the reduction of coupled, non-linear partial differential equations into coupled, non-linear ordinary differential equations. The algorithm for solving the resulting coupled, two-point, non-linear boundary value problem is presented in great detail in the paper. Extensive computation on velocity and temperature profiles is presented for a wide range of values of the parameters, for prescribed surface temperature (PST) and prescribed heat flux (PHF) boundary conditions. [Copyright &y& Elsevier]

Abstract: The simulation of cavitating flows is a challenging problem both in terms of modelling the physics and developing robust numerical methodologies. Such flows are characterized by important variations of the local Mach number, compressibility effects on turbulence and involve thermodynamic phase transition. To simulate these flows by applying homogeneous models and Reynolds averaged codes, the turbulence modelling plays a major role in the capture of unsteady behaviours. This paper presents a one-fluid compressible Reynolds-Averaged Navier–Stokes (RANS) solver with a simple equation of state (EOS) for the mixture. A special focus is devoted to the turbulence model influence. Unsteady numerical results are given for Venturi geometries and comparisons are made with experimental data. [ABSTRACT FROM AUTHOR]

A series of two- and three-dimensional stationary problems of a viscous incompressible fluid flow in a channel caused by a given pressure differential is studied in the paper. It is shown that the solution to this problem is not unique. A numerical method allowing one to obtain the solution without specifying additional conditions for the velocity components on the boundary is considered. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the effects of time delay on the flutter instability of an actively controlled airfoil in an incompressible flow field. Firstly, in view of the presence of time delays in the actual control system, multiple time delays in feedback loop are introduced to the present flutter suppression system. Next, the stability boundaries of the closed-loop system with multiple time delays are obtained by solving a polynomial eigenvalue problem, and are validated by numerical simulations. The results demonstrate that time delays in control loop have strong effects on the stability of controlled aeroelastic systems and should not be ignored in the design of the aeroservoelastic system of the aircraft. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the hyperelastic behaviour of single wall carbon nanotubes (SWCNTs) by means of a finite element-based lattice approach. A one-term incompressible Ogden-type hyperelastic model is chosen to describe the mechanical response of SWCNTs under tensile loading. In order to determine the material constants of the model, numerical tests are conducted on a representative arrangement of carbon atoms, establishing equality between the Ogden strain–energy and the variation of the Tersoff–Brenner interatomic potential. The material constants determined here are then used in numerical simulations carried out on SWCNTs models. A good predictive capability of the present model is found when the obtained results are compared to published data. A first conclusion obtained from the present work suggests that a value of 0.147nm for the Cuivalent diameter is suitable for the hyperelastic description of SWCNTs. A second conclusion reveals a prediction of 0.51 for the breaking strain of SWCNTs under tension, which is in excellent agreement with results obtained from molecular dynamics simulations and continuum theory. [ABSTRACT FROM AUTHOR]

Abstract: The use of particulate filters (DPF) in Diesel engines has become in recent years the standard technology for the control of soot aerosol emissions. Once emissions reduction through the management of filtration and regeneration aspects has reached its maturity, the effect of the system location on engine performance and acoustics are key topics to be addressed. In this paper, a fluid dynamic model for wall-flow monolith filters is described in which non-homentropic one-dimensional unsteady compressible flow is considered. The good agreement with experimental data confirms that the model is able to describe the mechanisms contributing to the pressure drop across the whole filter under steady and impulsive flow conditions. The approach of the flow governing equations provides a reliable evaluation of the contributions to the pressure drop with axial resolution in the description of the flow field properties. In addition, the frequency response predicted by the model confirms its ability to evaluate the dynamic response and acoustic potential of the DPF. [ABSTRACT FROM AUTHOR]

We study in this paper a P1 finite element approximation of the solution in of a biharmonic problem. Since the P1 finite element method only leads to an approximate solution in , a discrete Laplace operator is used in the numerical scheme. The convergence of the method is shown, for the general case of a solution with regularity, thanks to compactness results and to the use of a particular interpolation of regular functions with compact supports. An error estimate is proved in the case where the solution is in . The order of this error estimate is equal to 1 if the solution has a compact support, and only 1/5 otherwise. Numerical results show that these orders are not sharp in particular situations. [ABSTRACT FROM AUTHOR]

Abstract: In the following paper, we discuss the exhaustive use and implementation of stabilization finite element methods for the resolution of the 3D time-dependent incompressible Navier–Stokes equations. The proposed method starts by the use of a finite element variational multiscale (VMS) method, which consists in here of a decomposition for both the velocity and the pressure fields into coarse/resolved scales and fine/unresolved scales. This choice of decomposition is shown to be favorable for simulating flows at high Reynolds number. We explore the behaviour and accuracy of the proposed approximation on three test cases. First, the lid-driven square cavity at Reynolds number up to 50,000 is compared with the highly resolved numerical simulations and second, the lid-driven cubic cavity up to Re=12,000 is compared with the experimental data. Finally, we study the flow over a 2D backward-facing step at Re=42,000. Results show that the present implementation is able to exhibit good stability and accuracy properties for high Reynolds number flows with unstructured meshes. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a finite element simulation of the behaviour of a vertical pile subjected to a cyclic lateral loading. First, the choice of a suitable constitutive model is discussed. The analytical solution of the model equations for a monotonic triaxial compression is given, and the model is compared with monotonic and cyclic triaxial tests on dry Fontainebleau sand. Simulations of tests carried out on a model pile with the geotechnical centrifuge of the French Public Works Research Laboratory (LCPC) were then performed with the model parameters derived from the triaxial tests. Results are in good agreement with experiments. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a mathematical model used to simulate the restart of an axial, compressible and transient flow of a Bingham fluid in circular or annular pipes. The model is based on the mass and momentum conservation equations plus a state equation that relates pressure to density. The viscous effect is modeled by employing a friction factor approach. The governing equations are discretized by using the finite volume method with a first-order upwind scheme, and the resulting non-linear algebraic equations are then solved iteratively. The model results were corroborated by an analytical solution for Newtonian flows. Additionally, the results were also in reasonable agreement with results reported in the literature. We also conducted sensitivity analyses with respect to Reynolds number, aspect ratio, gravity and the non-linear advective terms of the governing equations. [Copyright &y& Elsevier]