Authors:Wojciech P. Adamczyk Pages: 669 - 702 Abstract: Abstract The numerical simulation of the large scale industrial circulating fluidized bed (CFB) boilers, working under air- and oxy-fuel combustion are presented in this paper. Moreover, two-dimensional experimental rig used for numerical model validation is described. For three-dimensional numerical simulations two industrial compact CFB boilers were selected installed in Polish Power Plants. Numerical simulations were carried out using three-dimensional model where the dense particulate transport phenomenon was simultaneously modelled with combustion process. The fluidization process was modelled using the hybrid Euler–Lagrange approach. Within the paper, readers can find information about used computational technique and a number of reference to specific work. The impact of radiative heat transfer on predicted temperature profile within the CFB boiler was investigated in presented work. Moreover, the novel model for retrieving radiative properties of gases under oxy-fuel combustion process was used. The evaluated temperature and pressure profiles during numerical simulations were compared against measured data collected during boiler air-fuel operation. Collected data was also used for validating numerical model of the oxy-fuel combustion model. Stability of the model and its sensitivity on changes of composition of the oxidizer were studied. This simulations were evaluated to check the response of the numerical model on changing the combustion conditions from air- to oxy-fuel combustion process. The comparison of the pressure and temperature profiles for all considered cases gave comparable trends in contrary to measured data. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9186-z Issue No:Vol. 24, No. 4 (2017)

Authors:David Greiner; Jacques Periaux; Jose M. Emperador; Blas Galván; Gabriel Winter Pages: 703 - 750 Abstract: Abstract A general review of game-theory based evolutionary algorithms (EAs) is presented in this study. Nash equilibrium, Stackelberg game and Pareto optimality are considered, as game-theoretical basis of the evolutionary algorithm design, and also, as problems solved by evolutionary computation. Applications of game-theory based EAs in computational engineering are listed, with special emphasis in structural optimization and, particularly, in skeletal structures. Additionally, a set of three problems are solved: reconstruction inverse problem, fully stressed design problem and minimum constrained weight, for discrete sizing of frame skeletal structures. We compare panmictic EAs, Nash EAs using 4 different static domain decompositions, including also a new dynamic domain decomposition. Two frame structural test cases of 55 member size and 105 member size are evaluated with the linear stiffness matrix method. Numerical experiments show the efficiency of the Nash EAs approach, confirmed with statistical significance analysis of results, and enhanced with the dynamic domain decomposition. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9187-y Issue No:Vol. 24, No. 4 (2017)

Authors:Walter Boscheri Pages: 751 - 801 Abstract: Abstract In this work we develop a new class of high order accurate Arbitrary-Lagrangian–Eulerian (ALE) one-step finite volume schemes for the solution of nonlinear systems of conservative and non-conservative hyperbolic partial differential equations. The numerical algorithm is designed for two and three space dimensions, considering moving unstructured triangular and tetrahedral meshes, respectively. As usual for finite volume schemes, data are represented within each control volume by piecewise constant values that evolve in time, hence implying the use of some strategies to improve the order of accuracy of the algorithm. In our approach high order of accuracy in space is obtained by adopting a WENO reconstruction technique, which produces piecewise polynomials of higher degree starting from the known cell averages. Such spatial high order accurate reconstruction is then employed to achieve high order of accuracy also in time using an element-local space–time finite element predictor, which performs a one-step time discretization. Specifically, we adopt a discontinuous Galerkin predictor which can handle stiff source terms that might produce jumps in the local space–time solution. Since we are dealing with moving meshes the elements deform while the solution is evolving in time, hence making the use of a reference system very convenient. Therefore, within the space–time predictor, the physical element is mapped onto a reference element using a high order isoparametric approach, where the space–time basis and test functions are given by the Lagrange interpolation polynomials passing through a predefined set of space–time nodes. The computational mesh continuously changes its configuration in time, following as closely as possible the flow motion. The entire mesh motion procedure is composed by three main steps, namely the Lagrangian step, the rezoning step and the relaxation step. In order to obtain a continuous mesh configuration at any time level, the mesh motion is evaluated by assigning each node of the computational mesh with a unique velocity vector at each timestep. The nodal solver algorithm preforms the Lagrangian stage, while we rely on a rezoning algorithm to improve the mesh quality when the flow motion becomes very complex, hence producing highly deformed computational elements. A so-called relaxation algorithm is finally employed to partially recover the optimal Lagrangian accuracy where the computational elements are not distorted too much. We underline that our scheme is supposed to be an ALE algorithm, where the local mesh velocity can be chosen independently from the local fluid velocity. Once the vertex velocity and thus the new node location has been determined, the old element configuration at time \(t^n\) is connected with the new one at time \(t^{n+1}\) with straight edges to represent the local mesh motion, in order to maintain algorithmic simplicity. The final ALE finite volume scheme is based directly on a space–time conservation formulation of the governing system of hyperbolic balance laws. The nonlinear system is reformulated more compactly using a space–time divergence operator and is then integrated on a moving space–time control volume. We adopt a linear parametrization of the space–time element boundaries and Gaussian quadrature rules of suitable order of accuracy to compute the integrals. We apply the new high order direct ALE finite volume schemes to several hyperbolic systems, namely the multidimensional Euler equations of compressible gas dynamics, the ideal classical magneto-hydrodynamics equations and the non-conservative seven-equation Baer–Nunziato model of compressible multi-phase flows with stiff relaxation source terms. Numerical convergence studies as well as several classical test problems will be shown to assess the accuracy and the robustness of our schemes. Finally we briefly present some variants of the algorithm that aim at improving the overall computational efficiency. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9188-x Issue No:Vol. 24, No. 4 (2017)

Authors:S. Ivvan Valdez; Salvador Botello; Miguel A. Ochoa; José L. Marroquín; Victor Cardoso Pages: 803 - 839 Abstract: Abstract This article proposes a benchmark set of problems for fixed mesh topology optimization in 2 dimensions. We have established the problems based on an analysis of more than 100 articles from the topology optimization specialized literature, gathering the most common dimensions, loads and fixed regions used by researchers. Most of the problems reported in specialized literature present differences in specifications such as lengths, units, materials among others. For instance, some articles propose the same proportions and geometrical shapes but different dimensions. Hence, the purpose of this benchmark is to unify geometrical and mechanical characteristics and load conditions, considering that the proposed problems must be realistic, in the sense that the units are in the International System and a real-world material and load conditions are used. The final benchmark integrates 13 problems for plane stress using ASTM A-36 steel. Additionally, we report approximations to the optimum solutions for both: compliance and volume minimization problems using the Solid Isotropic Material with Penalization (SIMP) and a novel version of SIMP proposed in this article. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9190-3 Issue No:Vol. 24, No. 4 (2017)

Authors:Nagaraj Murugesan; Vasudevan Rajamohan Pages: 841 - 853 Abstract: Abstract A review of recent developments in the progressive failure analysis of laminated composite structural elements such as beams, plates, panels and shells is presented in this paper. Composite materials are increasingly used to harness their advantages such as high strength to light weight, easy fabrication of structural components to the desired complicated geometry particularly in aerospace structures. Since the failure of composite laminates are progressive in nature compared to their metallic counter parts, it signifies to have better analysis methods to predict the progressive failure of laminated composites. A vast number of researches have taken place in this field. A few of the most relevant research articles are reviewed and presented here briefly. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9191-2 Issue No:Vol. 24, No. 4 (2017)

Authors:Mohammad Junaid Khan; Lini Mathew Pages: 855 - 867 Abstract: Abstract In modern years due to rising environmental issues such as energy cost and greenhouse gas emission have motivated new research into alternative methods of generation of electrical power. A vast deal of new research and enlargement for the renewable energy photovoltaic (PV) system. The PV module is conducted to search out non-polluting and renewable sources. New inventions are in development and exploring the perfection of solar cells to increase the efficiency and reduce the cost of power in per peak watt. The analysis of different kinds of control methods in PV system according to reviewed previous studies, shows that the most useful method is a hybrid technique as compared to other maximum power point tracking (MPPT) control methods. MPPT control method used to optimize the output of solar PV system with variable inputs such as solar radiations and temperature. The MPPT may include the use of a different DC–DC converter and also some different MPPT algorithms such as current based MPPT. Multi-input energy systems for the hybrid wind/solar energy systems need to be developed. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9192-1 Issue No:Vol. 24, No. 4 (2017)

Authors:Konrad Perzynski; Lukasz Madej Pages: 869 - 890 Abstract: Abstract Development of a discrete/continuum numerical model of different failure modes operating in dual phase steels during deformation is the main goal of the research. Proposed approach is based on a random cellular automata (RCA) model incorporated in a fully coupled manner to the finite element (FE) framework. As a result, the RCAFE model that can take into account fracture initiation within martensite phase, delamination between martensite and ferrite phases, ferrite phase fracture and delamination between ferrite and ferrite grain boundaries was established. Details on the developed cellular automata model including random space definition, state of CA cells as well as properly defined transition rules are recapitulated in the work. Developed data bridging technique between RCA and FE models is discussed within that part. Particular attention, however, is put on model parameters identification stage, which was realized with the inverse analysis technique on the basis of in situ tensile tests. Finally, examples of model application to multiscale numerical simulation of three point bending, which was selected as a case study, are presented to highlight predictive capabilities of the developed RCAFE solution. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9195-y Issue No:Vol. 24, No. 4 (2017)

Authors:Tao He; Kai Zhang Pages: 891 - 934 Abstract: Abstract This review article summarizes the basis and recent developments on the combined interface boundary condition (CIBC) method for the numerical simulation of fluid–structure interaction (FSI) problems. To represent the continual reciprocity between both media better, the CIBC method employs a Gauss–Seidel-like procedure to transform the traditional interface conditions into the velocity and traction corrections. A free parameter is adopted to control the effect of such a treatment on the fluid–structure interface. The thorough derivation of the CIBC method is presented, hence providing the theoretical basis of two improved formulations of the method. The relevant issues are deeply discussed for the numerical implementation. The CIBC method is subsequently introduced into various partitioned solution schemes. After describing all ingredients of our coupling strategies in detail, intensive FSI examples are tested to justify the feasibility, robustness and efficiency of the developed methodologies. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9193-0 Issue No:Vol. 24, No. 4 (2017)

Authors:H. Zakeri; Fereidoon Moghadas Nejad; Ahmad Fahimifar Pages: 935 - 977 Abstract: Abstract Pavement condition information is a significant component in Pavement Management Systems. The labeling and quantification of the type, severity, and extent of surface cracking is a challenging area for weighing the asphalt pavements. This paper presents a widespread review on various platform and image processing approaches for asphalt surface interpretation. The main part of this study presents a comprehensive combination of the state of the art in image processing based on crack interpretation related to asphalt pavements. An attempt is made to study the existing methodologies from different points of views accompanied by extensive comparisons on three stages of methods—distress detection, classification, and quantification to facilitate further research studies. This paper presents a survey of the developed pavement inspection systems up to date. Additionally, emerging and evolution technologies considered to automate the processes are discussed. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9194-z Issue No:Vol. 24, No. 4 (2017)

Authors:Prateek Dixit; G. R. Liu Pages: 979 - 1031 Abstract: Abstract This paper presents an overview of the published major finite element (FE) models for simulating injuries of human brains, based on our recent comprehensive literature study on the published works since early 2000 to date. Our focus is on studies of the so-called mild traumatic brain injuries (MTBI) that have always been a major concern with respect to various contact sports, including boxing and football. In addition, papers on the investigations of various types of accidents as major cause of MTBI have also reviewed. Because concussion is known as one of the main reasons for a MTBI, and addressing it has been a pressing need in recent times. FE models have been frequently used to study the mechanism of concussions, and different types of models with various considerations have been included in this review study. This paper aims to summarize all these published efforts, models, data, finings, and understandings of concussion mechanisms reported in the open literature. We hope this can serve a useful source for initial studies for researchers planning to invest their time and energy in the investigations in the related areas. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9196-x Issue No:Vol. 24, No. 4 (2017)

Authors:G. Houzeaux; J. C. Cajas; M. Discacciati; B. Eguzkitza; A. Gargallo-Peiró; M. Rivero; M. Vázquez Pages: 1033 - 1070 Abstract: Abstract Domain composition methods (DCM) consist in obtaining a solution to a problem, from the formulations of the same problem expressed on various subdomains. These methods have therefore the opposite objective of domain decomposition methods (DDM). Indeed, in contrast to DCM, these last techniques are usually applied to matching meshes as their purpose consists mainly in distributing the work in parallel environments. However, they are sometimes based on the same methodology as after decomposing, DDM have to recompose. As a consequence, in the literature, the term DDM has many times substituted DCM. DCM are powerful techniques that can be used for different purposes: to simplify the meshing of a complex geometry by decomposing it into different meshable pieces; to perform local refinement to adapt to local mesh requirements; to treat subdomains in relative motion (Chimera, sliding mesh); to solve multiphysics or multiscale problems, etc. The term DCM is generic and does not give any clue about how the fragmented solutions on the different subdomains are composed into a global one. In the literature, many methodologies have been proposed: they are mesh-based, equation-based, or algebraic-based. In mesh-based formulations, the coupling is achieved at the mesh level, before the governing equations are assembled into an algebraic system (mesh conforming, Shear-Slip Mesh Update, HERMESH). The equation-based counterpart recomposes the solution from the strong or weak formulation itself, and are implemented during the assembly of the algebraic system on the subdomain meshes. The different coupling techniques can be formulated for the strong formulation at the continuous level, for the weak formulation either at the continuous or at the discrete level (iteration-by-subdomains, mortar element, mesh free interpolation). Although the different methods usually lead to the same solutions at the continuous level, which usually coincide with the solution of the problem on the original domain, they have very different behaviors at the discrete level and can be implemented in many different ways. Eventually, algebraic-based formulations treat the composition of the solutions directly on the matrix and right-hand side of the individual subdomain algebraic systems. The present work introduces mesh-based, equation-based and algebraic-based DCM. It however focusses on algebraic-based domain composition methods, which have many advantages with respect to the others: they are relatively problem independent; their implicit implementation can be hidden in the iterative solver operations, which enables one to avoid intensive code rewriting; they can be implemented in a multi-code environment. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9198-8 Issue No:Vol. 24, No. 4 (2017)

Authors:Guillermo Vilanova; Ignasi Colominas; Hector Gomez Pages: 1071 - 1102 Abstract: Abstract Angiogenesis is the growth of new capillaries from preexisting ones. The ability to trigger angiogenesis is one of the hallmarks of cancer, and is a necessary step for a tumor to become malignant. This paper discusses computational modeling of tumor-induced angiogenesis with particular reference to mathematical modeling, numerical simulation, and comparison with experiments. We describe the basic biological phenomena associated with angiogenesis, and discuss how they can be incorporated into mathematical models. We emphasize the crucial role of numerical methods for model development. In particular, computational methods for tumor angiogenesis need to be geometrically flexible and capable of dealing with higher-order derivatives, which suggests isogeometric analysis as an ideal candidate. Finally, we propose an algorithm based on graph theory as a potential method for quantitative validation of tumor angiogenesis models. PubDate: 2017-11-01 DOI: 10.1007/s11831-016-9199-7 Issue No:Vol. 24, No. 4 (2017)

Authors:Santiago Badia; Alberto F. Martín; Javier Principe Abstract: FEMPAR is an open source object oriented Fortran200X scientific software library for the high-performance scalable simulation of complex multiphysics problems governed by partial differential equations at large scales, by exploiting state-of-the-art supercomputing resources. It is a highly modularized, flexible, and extensible library, that provides a set of modules that can be combined to carry out the different steps of the simulation pipeline. FEMPAR includes a rich set of algorithms for the discretization step, namely (arbitrary-order) grad, div, and curl-conforming finite element methods, discontinuous Galerkin methods, B-splines, and unfitted finite element techniques on cut cells, combined with h-adaptivity. The linear solver module relies on state-of-the-art bulk-asynchronous implementations of multilevel domain decomposition solvers for the different discretization alternatives and block-preconditioning techniques for multiphysics problems. FEMPAR is a framework that provides users with out-of-the-box state-of-the-art discretization techniques and highly scalable solvers for the simulation of complex applications, hiding the dramatic complexity of the underlying algorithms. But it is also a framework for researchers that want to experience with new algorithms and solvers, by providing a highly extensible framework. In this work, the first one in a series of articles about FEMPAR, we provide a detailed introduction to the software abstractions used in the discretization module and the related geometrical module. We also provide some ingredients about the assembly of linear systems arising from finite element discretizations, but the software design of complex scalable multilevel solvers is postponed to a subsequent work. PubDate: 2017-10-11 DOI: 10.1007/s11831-017-9244-1

Authors:Carlos A. Felippa; Eugenio Oñate; Sergio R. Idelsohn Abstract: Abstract This is part of an article series on a variational framework for continuum mechanics based on the Finite Increment Calculus (FIC). The formulation utilizes high order derivatives of the classical fields of continuum mechanics integrated over control regions to construct stabilizing modification terms. Fields may include displacements, body forces, strains, stresses, pressure and volumetric strains. To support observer-invariant FIC formulations, we have catalogued field transformation equations as well as sets of linear and quadratic invariants of fields and of their derivatives up to appropriate order. Attention is focused on the two-dimensional case of a body in plane strain under the drilling-rotation transformation group. Results are presented for displacement and body-force derivatives of orders up to 4, and for stress, strain, pressure and volumetric strain derivatives of order up to 3. The material assembled here is self-contained because this catalog is believed to be useful beyond FIC applications; for example gradient-based, nonlocal constitutive models of multiscale mechanics and physics that involve finite characteristic dimensions analogous to FIC steplengths. PubDate: 2017-10-10 DOI: 10.1007/s11831-017-9245-0

Authors:Alireza Kharazian; Francisco López-Almansa Abstract: Abstract Collision between adjoining buildings with aligned slabs is relevant, since the huge impact forces significantly modify the buildings dynamic behavior. The separation required by the regulations avoids pounding; however, even in recent buildings, impact can occur due to not fulfillment of codes and seismicity underestimation. Given the importance of this issue, a significant research effort has been undertaken worldwide, and a considerable number of papers are available. The complexity of this field and this abundance of information might require a review task. This paper presents a summary of the theoretical developments, discusses the most common simulation software, provides an overview of the previous research, offers recommendations to researchers, and identifies research needs. PubDate: 2017-09-14 DOI: 10.1007/s11831-017-9242-3

Authors:Patrick Gallinari; Yvon Maday; Maxime Sangnier; Olivier Schwander; Tommaso Taddei Abstract: Abstract Reduced basis methods for the approximation to parameter-dependent partial differential equations are now well-developed and start to be used for industrial applications. The classical implementation of the reduced basis method goes through two stages: in the first one, offline and time consuming, from standard approximation methods a reduced basis is constructed; then in a second stage, online and very cheap, a small problem, of the size of the reduced basis, is solved. The offline stage is a learning one from which the online stage can proceed efficiently. In this paper we propose to exploit machine learning procedures in both offline and online stages to either tackle different classes of problems or increase the speed-up during the online stage. The method is presented through a simple flow problem—a flow past a backward step governed by the Navier Stokes equations—which shows, however, interesting features. PubDate: 2017-08-05 DOI: 10.1007/s11831-017-9238-z

Authors:Jan Neggers; Olivier Allix; François Hild; Stéphane Roux Abstract: Abstract Since the turn of the century experimental solid mechanics has undergone major changes with the generalized use of images. The number of acquired data has literally exploded and one of today’s challenges is related to the saturation of mining procedures through such big data sets. With respect to digital image/volume correlation one of tomorrow’s pathways is to better control and master this data flow with procedures that are optimized for extracting the sought information with minimum uncertainties and maximum robustness. In this paper emphasis is put on various hierarchical identification procedures. Based on such structures a posteriori model/data reductions are performed in order to ease and make the exploitation of the experimental information far more efficient. Some possibilities related to other model order reduction techniques like the proper generalized decomposition are discussed and new opportunities are sketched. PubDate: 2017-07-28 DOI: 10.1007/s11831-017-9234-3

Authors:Domenico Borzacchiello; José V. Aguado; Francisco Chinesta Abstract: Abstract We discuss the use of hierarchical collocation to approximate the numerical solution of parametric models. With respect to traditional projection-based reduced order modeling, the use of a collocation enables non-intrusive approach based on sparse adaptive sampling of the parametric space. This allows to recover the low-dimensional structure of the parametric solution subspace while also learning the functional dependency from the parameters in explicit form. A sparse low-rank approximate tensor representation of the parametric solution can be built through an incremental strategy that only needs to have access to the output of a deterministic solver. Non-intrusiveness makes this approach straightforwardly applicable to challenging problems characterized by nonlinearity or non affine weak forms. As we show in the various examples presented in the paper, the method can be interfaced with no particular effort to existing third party simulation software making the proposed approach particularly appealing and adapted to practical engineering problems of industrial interest. PubDate: 2017-07-18 DOI: 10.1007/s11831-017-9241-4