Authors:Jaesoon Jung; Junghwan Kook; Seongyeol Goo; Semyung Wang Pages: 1 - 15 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Jaesoon Jung, Junghwan Kook, Seongyeol Goo, Semyung Wang In this paper, an accurate and efficient numerical method for sound transmission analysis is presented. As an alternative to conventional numerical methods, such as the Finite Element Method (FEM), Boundary Element Method (BEM) and Statistical Energy Analysis (SEA), the FE-ERA method, which combines the FEM and Elementary Radiator Approach (ERA) is proposed. The FE-ERA method analyzes the vibrational response of the plate structure excited by incident sound using FEM and then computes the transmitted acoustic pressure from the vibrating plate using ERA. In order to improve the accuracy and efficiency of the FE-ERA method, a novel criterion for the optimal number of elementary radiators is proposed. The criterion is based on the radiator error index that is derived to estimate the accuracy of the computation with used number of radiators. Using the proposed criterion a radiator selection method is presented for determining the optimum number of radiators. The presented radiator selection method and the FE-ERA method are combined to improve the computational accuracy and efficiency. Several numerical examples that have been rarely addressed in previous studies, are presented with the proposed method. The accuracy and efficiency of the proposed method are validated by comparison with the results of the three dimensional (3D) FEM structure-acoustic interaction models.
Authors:Benoit Bary; Christophe Bourcier; Thomas Helfer Pages: 16 - 30 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Benoit Bary, Christophe Bourcier, Thomas Helfer We investigate in this paper analytically and numerically by means of 3D simulations the viscoelastic behavior of concrete and mortar subjected to creep loading and moderate temperatures at mesoscale. These heterogeneous materials are assumed to be composed of thermoelastic aggregates distributed in a linear thermoviscoelastic matrix; moreover, the Interfacial Transition Zones (ITZ) between aggregates and matrix, whose behavior is also considered as linear thermoviscoelastic, are explicitly introduced. The numerical specimens consist in unstructured periodic meshes containing polyhedral aggregates with various size and shapes randomly distributed in a box. Zero-thickness interface finite elements are introduced between aggregates and matrix to model the ITZ. Macroscopic response and averaged stresses and strains in the matrix and aggregate phases are compared to analytical estimations obtained with classical mean-field approximation schemes applied in the Laplace–Carson space, in which the ITZ are introduced via imperfect interfaces modeled with the Linear Spring Model (LSM). The effects of ITZ thickness, aggregate shape and uniform temperature increase are then studied to evaluate their respective influence on the local and macroscopic creep behavior of mortar and concrete. Globally, it is found that the model response is in relatively good agreement with numerical simulations results, and that as expected while the ITZ do not affect significantly the concrete behavior, they have a non-negligible impact on the mortar one.
Authors:R.L. Pedro; J. Demarche; L.F.F. Miguel; R.H. Lopez Pages: 31 - 45 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): R.L. Pedro, J. Demarche, L.F.F. Miguel, R.H. Lopez This paper presents an efficient two-stage optimization approach to the design of steel-concrete composite I-girder bridges. In the first step, a simplified structural model, usually adopted by bridge designers, is employed aiming to locate the global optimum region and provide a starting point to the local search. Then, a finite element model (FEM) is used to refine and improve the optimization. Through this procedure, it is possible to combine the low computational cost required on the first stage with the accuracy provided on the second one. For illustration purposes, a numerical example of a composite bridge designed by Pinho and Bellei (2007) and studied by Leitao et al. (2011) is assessed. The objective function is based on the material cost of the structure. Due to the non-convex nature of the problem and to the presence of discrete variables, the first stage optimization is conducted through five well-known meta-heuristic algorithms: Backtracking Search Algorithm (BSA), Firefly Algorithm (FA), Genetic Algorithm (GA), Imperialist Competitive Algorithm (ICA) and Search Group Algorithm (SGA). The SGA is chosen to pursue the second stage because a statistical analysis has shown that it achieved the best performance. It is shown that the proposed scheme is able to reduce the structural cost in up to 7.43% already in the first stage and can reach up to 9.17% of saving costs in the end of the optimization procedure.
Authors:Sara Casciati; Michele Vece Pages: 46 - 53 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Sara Casciati, Michele Vece The real time estimation of the displacements of civil structures is quite sensitive to the availability of wired links between the sensors and the remote control room. Many kinds of wireless displacement sensors or indirect measurements of them have been proposed. However, most of them suffer of large time delays and accuracy issues. In this paper, the authors adopt a Kalman-filter-based data fusion to make a precise measurement of the displacements in for civil structures and infrastructures. The required accuracy can be reached exploiting the real-time satellite corrections provided by a single reference station and combining them with the acceleration signals coming from three axial accelerometers. A wireless communication transfers the information coming from the coupling of GNSS receivers and three axial accelerometers. The proposed system is validated by control mechanism and laboratory tests. The ultimate goal is a reliable scheme for a real-time structural health monitoring managed in remote control.
Authors:A.A. Kruglov; V.R. Ganieva; F.U. Enikeev Pages: 54 - 65 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): A.A. Kruglov, V.R. Ganieva, F.U. Enikeev The problem to determine experimentally the values of material parameters for two material models of superplastic flow, σ=Kξm and σ = K′ξ m′ε n , from the results of technological trials is considered. With this in view, a special computational procedure is developed to minimize the deviation of the theoretically predicted forming times from experimental data recorded during constant pressure forming trials of a sheet into a circular die. As compared with similar procedures known in the literature the methods suggested enable one to obtain a unique set of material parameters by using the whole set of available experimental data. The validity of the procedures suggested is confirmed by means of comparing the results obtained with corresponding finite element solutions. The accuracy of modeling of the experimentally measured values of the forming time is found to be better than 5% for all cases considered.
Authors:Shanghong Zhang; Wenda Li; Xiaohui Lei; Xiaowen Ding; Tianxiang Zhang Pages: 66 - 75 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Shanghong Zhang, Wenda Li, Xiaohui Lei, Xiaowen Ding, Tianxiang Zhang Computer-based flow visualization, which is an important approach to examine both the dynamic flow process and to elucidate the laws of fluid movement, can greatly facilitate our understanding of the complicated hydrologic cycle and provide insights into regional water resources management. Nevertheless, at present, few software tools can efficiently perform different flow visualizations for watershed modeling. In this study, a virtual watershed platform was developed and various implementation methods of flow visualization were assessed, such as scalar field visualization, vector field visualization, and visual water effects. In the platform, spatially distributed flow model results and georeferenced datasets are visualized in a virtual 3D environment. End users can conveniently explore modeling results within that environment. Based on analysis of the varying requirements of the flow visualization methods applied to watershed simulation, overheads associated with a user-determined switch between different systems were reduced, and the level of comprehensive information management and analysis of large volumes of watershed data was improved. This study shows that application of the watershed platform can enhance flow visualization in the water resources research community, and makes related water modeling more practical in support of water resources management.
Authors:D. Dinh-Cong; T. Vo-Duy; V. Ho-Huu; H. Dang-Trung; T. Nguyen-Thoi Pages: 76 - 87 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): D. Dinh-Cong, T. Vo-Duy, V. Ho-Huu, H. Dang-Trung, T. Nguyen-Thoi The paper presents an efficient multi-stage optimization approach for damage detection in plate-like structures. In this approach, the damage identification process is achieved by minimizing an objective function established via flexibility changes of the structure. The vector of design variables represents correspondingly the damage extent of elements discretized by the finite element model. For analyzing the response of plate structures, the finite element model using 9-node quadratic quadrilateral elements is applied. For solving the optimization problem, a modified differential evolution (MDE) algorithm, which can help enhance the balance of global and local searches in each generation, is used for many stages of damage detection, in which the low damage variables in each stage are gradually eliminated after several generations to reduce the dimension of searching space and to increase the convergence rate of the problem. The efficiency of the proposed method is investigated through two numerical examples for isotropic and laminated composite plates. The obtained results indicate that the proposed method not only successfully detects the location and severity of multi-damage cases in the plate structures, but also show the better efficiency in term of computational cost.
Authors:Matthew Gutowski; Emre Palta; Howie Fang Pages: 88 - 100 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Matthew Gutowski, Emre Palta, Howie Fang With an average of six billion miles traveled per day on U.S. highways, according to the Federal Highway Administration (FHWA), transportation safety is of the utmost importance. Over the years, various traffic barrier systems, including W-beam guardrails, have been developed to reduce the number and severity of vehicle crashes. Despite their general effectiveness, improvements could be made, especially when installed on unlevelled terrains such as sloped medians. The destructive nature of crashes imposes significant challenges to barrier design using full-scale physical testing; numerical simulations thus become a viable means to support crash analysis, performance evaluation, and barrier designs. In this study, validated vehicle and W-beam models were used to perform full-scale simulations of vehicle-guardrail impacts. Fourteen single-faced and double-faced NCDOT W-beam guardrails (with placement heights of 29 and 31 inches) placed along a six-lane 46-foot median divided highway with 2.5H:1V and 4H:1V slopes were evaluated under front-side and backside vehicular impacts. The guardrails performance was determined by evaluating the vehicular responses based on MASH exit-box criterion, post-impact exit trajectory, yaw, pitch, and roll angles, transverse displacements, and transverse velocities.
Authors:Seung-Ho Ham; Myung-Il Roh; Hyewon Lee; Jin-Wuk Hong; Hong-Rae Lee Pages: 101 - 116 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Seung-Ho Ham, Myung-Il Roh, Hyewon Lee, Jin-Wuk Hong, Hong-Rae Lee The motions of the mega floating crane and the lifted module must be evaluated in advance, to determine whether they satisfy the safety criteria or not. Due to the limitations of the existing dynamic analysis programs, we develop a differentiated program that is dedicated to the mega floating crane. This program is focused on reducing modeling time, while increasing modeling accuracy. Furthermore, it can model the block loader that distributes the tension in wire ropes between the lifted module and the block loader equally, and link beams that are used to connect hooks by hinge joints. The equations of motion based on multibody system dynamics are derived. Wave, wind, and current are included as external environmental loads. A direct volume calculation method below the water plane is adopted to find the buoyant force and center of buoyancy. External loads are verified by commercial program. Finally, the simulation results of the module erection are validated by comparison with the measurement of real operation.
Authors:Hai Du; Muguo Li; Juan Meng Pages: 117 - 123 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Hai Du, Muguo Li, Juan Meng Research on changes in the fluid edge of a wave flume is important for experimental hydrodynamics. However, disturbances often occur because of the presence of sensors. To solve this problem, a new grey-scale image processing method for fluid edge analysis is presented here. By fusing methods combining image gradients and image segmentation with shifting-window technology and with concepts derived from experimental fluid mechanics, the proposed method can overcome many of the inherent challenges of fluid-edge measurement. First, the geodesic distance is modified to obtain a class curve. Second, an edge position is determined by the inflection point of the class curve related to the gradient peak distribution. Next, the position of the interrogation window is relocated with reference to neighbors or to previous results, and the current edge position can be calculated according to the predicted value. During the computation, the interrogation window can change its position adaptively with fluid motion, ensuring that the amount of data to be analyzed always remains stable. A model combining the class curve and gradient curve can improve the validity of edge identification. Finally, the performance of the proposed method has been evaluated using images in a glass flume. The results show that the proposed method for studying the fluid edge is effective and robust.
Authors:Michal Merta; Lubomir Riha; Ondrej Meca; Alexandros Markopoulos; Tomas Brzobohaty; Tomas Kozubek; Vit Vondrak Pages: 124 - 135 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Michal Merta, Lubomir Riha, Ondrej Meca, Alexandros Markopoulos, Tomas Brzobohaty, Tomas Kozubek, Vit Vondrak This paper describes an approach for acceleration of the Hybrid Total FETI (HTFETI) domain decomposition method using the Intel Xeon Phi coprocessors. The HTFETI method is a memory bound algorithm which uses sparse linear BLAS operations with irregular memory access pattern. The presented local Schur complement (LSC) method has regular memory access pattern, that allows the solver to fully utilize the Intel Xeon Phi fast memory bandwidth. This translates to speedup over 10.9 of the HTFETI iterative solver when solving 3 billion unknown heat transfer problem (3D Laplace equation) on almost 400 compute nodes. The comparison is between the CPU computation using sparse data structures (PARDISO sparse direct solver) and the LSC computation on Xeon Phi. In the case of the structural mechanics problem (3D linear elasticity) of size 1 billion DOFs the respective speedup is 3.4. The presented speedups are asymptotic and they are reached for problems requiring high number of iterations (e.g., ill-conditioned problems, transient problems, contact problems). For problems which can be solved with under hundred iterations the local Schur complement method is not optimal. For these cases we have implemented sparse matrix processing using PARDISO also for the Xeon Phi accelerators.
Authors:J. Calvo; J. Gracia; E. Bayo Pages: 136 - 146 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): J. Calvo, J. Gracia, E. Bayo Current trends in web application development favours bi-directional communication between front-end and back-end applications instead of the traditional ones where the front-end is constantly monitoring the back-end. This way of communication improves the user experience and this work tries to find the best bi-directional way of communication particularized to structural analysis software as a service or web applications. The effects of the most significant factors have been studied to optimize the total time involved in the communication, which is comprised of: time spent sending data from the client to the server, server data processing, and time consumed returning the data back. Design of experiments (DoE) techniques have been used to characterize the influence of four factors: serialization language, communication protocol, amount of data (size of the structure measured by the number of elements), and server post-processing. Moreover, factors like server workload and network congestion have also been addressed. The first factor is dealt with as a nuisance factor whose influence is to be minimized, and the second one as an uncontrollable variable.
Authors:Wenzhen Qu; Yaoming Zhang; Yan Gu; Fajie Wang Pages: 147 - 153 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Wenzhen Qu, Yaoming Zhang, Yan Gu, Fajie Wang Thermal stress analysis is one of key aspects in mechanical design. Based on the indirect boundary integral equation (BIE) and the radial integration method (RIM), this paper develops a boundary-only element method for the boundary stress analysis of three-dimensional (3D) static thermoelastic problems. A transformation system constructed with the normal and two special tangential vectors is used to regularize the singularity in the indirect BIE. The RIM is then employed to transform the domain integrals arising in both displacement and its derivative integral equations into the equivalent boundary integrals, which results in a pure boundary discretized algorithm. Several numerical experiments are provided to verify the accuracy and convergence of the present approach.
Authors:Hanfeng Yin; Youye Xiao; Guilin Wen; Hongbing Fang Pages: 154 - 164 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Hanfeng Yin, Youye Xiao, Guilin Wen, Hongbing Fang As one of the most widely used safety devices on highways, W-beam guardrail plays an important role in protecting errant vehicles from entering dangerous zones or colliding with oncoming vehicles. As one of the most widely used safety devices on highways, W-beam guardrails play an important role in protecting errant vehicles from entering dangerous zones or colliding with oncoming vehicles. One common issue with the traditional W-beam guardrails (TWG) is tire snagging which often occurred when the wheel of a striking vehicle entangled with a guardrail post. Tire snagging reduces the redirection performance of the guardrail and can result in serious injuries to the occupants. In this study, a new W-beam guardrail, named as “η-shaped W-beam guardrail (η-WG)”, was developed using nonlinear finite element simulations combined with metamodeling-based design optimization methodology. The simulation results showed that tire snagging did not occur on the η-WG and the optimum design of the η-WG had an improved safety performance in vehicular crashes.
Authors:Jelena Ninić; Christian Koch; Janosch Stascheit Pages: 165 - 179 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Jelena Ninić, Christian Koch, Janosch Stascheit Building and construction information modelling for decision making during the life cycle of infrastructure projects are vital tools for the analysis of complex, integrated, multi-disciplinary systems. The traditional design process is cumbersome and involves significant manual, time-consuming preparation and analysis as well as significant computational resources. To ensure a seamless workflow during the design and analysis and to minimise the computation time, we propose a novel concept of multi-level numerical simulations, enabling the modelling on different Levels of Detail (LoDs) for each physical component, process information, and analysis type. In this paper, we present SATBIM, an integrated platform for information modelling, structural analysis and visualisation of the mechanised tunnelling process for design support. Based on a multi-level integrated parametric Tunnel Information Model, numerical models for each component on different LoDs are developed, considering proper geometric as well as material representation, interfaces and the representation of the construction process. Our fully automatic modeller for arbitrary tunnel alignments provides a high degree of automation for the generation, the setup and the execution of the simulation model, connecting the multi-level information model with the open-source simulation software KRATOS. The software of SATBIM is organized in a modular way in order to offer high flexibility not only for further extensions, but also for adaptation to future improvements of the simulation software. The SATBIM platform enables practical, yet flexible and user-friendly generation of the tunnel structure for arbitrary alignments on different LoDs, supporting the design process and providing an insight into soil-structure interactions during construction.
Authors:Giuseppe Bianchi; Sham Rane; Ahmed Kovacevic; Roberto Cipollone Pages: 180 - 191 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Giuseppe Bianchi, Sham Rane, Ahmed Kovacevic, Roberto Cipollone The limiting factor for the employment of advanced 3D CFD tools in the analysis and design of rotary vane machines is the unavailability of methods for generation of a computational grid suitable for fast and reliable numerical analysis. The paper addresses this issue through an analytical grid generation based on the user defined nodal displacement which discretizes the moving and deforming fluid domain of the sliding vane machine and ensures conservation of intrinsic quantities by maintaining the cell connectivity and structure. Mesh boundaries are defined as parametric curves generated using trigonometrical modelling of the axial cross section of the machine while the distribution of computational nodes is performed using algebraic algorithms with transfinite interpolation, post orthogonalisation and smoothing. Algebraic control functions are introduced for distribution of nodes on the rotor and casing boundaries in order to achieve good grid quality in terms of cell size and expansion. For testing of generated grids, single phase simulations of an industrial air rotary vane compressor are solved by use of commercial CFD solvers FLUENT and CFX. This paper presents implementation of the mesh motion algorithm, stability and robustness experienced with the solvers when working with highly deforming grids and the obtained flow results.
Authors:Jianguang Fang; Na Qiu; Xiuzhe An; Fenfen Xiong; Guangyong Sun; Qing Li Pages: 192 - 199 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Jianguang Fang, Na Qiu, Xiuzhe An, Fenfen Xiong, Guangyong Sun, Qing Li Hybrid structures with different materials have aroused increasing interest for their lightweight potential and excellent performances. This study explored the optimization design of steel–aluminum hybrid structures for the highly nonlinear impact scenario. A metamodel based multi-response objective-oriented sequential optimization was adopted, where Kriging models were updated with sequential training points. It was indicated that the sequential sampling strategy was able to obtain a much higher local accuracy in the neighborhood of the optimum and thus to yield a better optimum, although it did lead to a worse global accuracy over the entire design space. Furthermore, it was observed that the steel–aluminum hybrid structure was capable of decreasing the peak force and simultaneously enhancing the energy absorption, compared to the conventional mono-material structure.
Authors:Ge Yang; Bin Wu; Ge Ou; Zhen Wang; Shirley Dyke Pages: 200 - 210 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Ge Yang, Bin Wu, Ge Ou, Zhen Wang, Shirley Dyke Hybrid simulation has been demonstrated to be a powerful method to evaluate the system-level dynamic performance of structure. With the numerical substructure analyzed with finite element software and the difficult-to-model components tested with an experimental substructure, complex structures with sophisticated behaviors can readily be examined through a hybrid simulation. To coordinate and synchronize the substructures in hybrid simulation, software is required. In recent studies, model updating has been integrated into hybrid simulation to improve testing accuracy by updating the numerical model during the analysis. However, online model updating scheme requires some modifications in the typical hybrid simulation testing procedure, and this greater complexity is entailed in its implementation regarding the collaboration of identification algorithms with existing hybrid simulation software. To address this issue and broaden the utilization of hybrid simulation with model updating, an existing platform named HyTest originally for conventional hybrid simulation is extended for this purpose. This version of HyTest facilitates the online identification of material constitutive parameters using experimental measurements in its finite element based identification module. It also includes a data center with a uniform data transmission protocol to incorporate different substructures and modules. A numerical example is used to demonstrate the online identification of material parameters for concrete and steel models in a reinforced column, and to verify the accuracy of the identification module. Lastly the effectiveness of HyTest in conducting hybrid simulation with model updating is validated using actual hybrid tests on a steel frame.
Authors:Yixian Du; Hanzhao Li; Zhen Luo; Qihua Tian Pages: 211 - 221 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Yixian Du, Hanzhao Li, Zhen Luo, Qihua Tian To improve the poor shear performance of periodic lattice structure consisting of hexagonal unit cells, this study develops a new computational design method to apply topology optimization to search the best topological layout for lattice structures with enhanced shear stiffness. The design optimization problem of micro-cellular material is formulated based on the properties of macrostructure to maximize the shear modulus under a prescribed volume constraint using the energy-based homogenization method. The aim is to determine the optimal distribution of material phase within the periodic unit cell of lattice structure. The proposed energy-based homogenization procedure utilizes the sensitivity filter technique, especially, a modified optimal algorithm is proposed to evolve the microstructure of lattice materials with distinct topological boundaries. A high shear stiffness structure is obtained by solving the optimization model. Then, the mechanical equivalent properties are obtained and compared with those of the hexagonal honeycomb sandwich structure using a theoretical approach and the finite element method (FEM) according to the optimized structure. It demonstrates the effectiveness of the proposed method in this paper. Finally, the structure is manufactured, and then the properties are tested. Results show that the shear stiffness and bearing properties of the optimized lattice structure is better than that of the traditional honeycomb sandwich structure. In general, the proposed method can be effectively applied to the design of periodic lattice structures with high shear resistance and super bearing property.
Authors:Yu-Fen Cheng; Feng-Nan Hwang Pages: 222 - 230 Abstract: Publication date: October 2017 Source:Advances in Engineering Software, Volume 112 Author(s): Yu-Fen Cheng, Feng-Nan Hwang Many scientific and engineering applications require accurate, fast, robust, and scalable numerical solution of large sparse algebraic polynomial eigenvalue problems (PEVP’s) that arise from some appropriate discretization of partial differential equations. The polynomial Jacobi-Davidson (PJD) algorithm has been numerically shown as a promising approach for the PEVP’s to finding the interior spectrum. The PJD algorithm is a subspace method, which extracts the candidate eigenpair from a search space and the space updated by embedding the solution of the correction equation at the JD iteration. In this research, we develop and study the two-level PJD algorithm for PEVP’s with emphasis on the application of the dissipative acoustic cubic eigenvalue problem. The proposed two-level PJD algorithm consists of two important ingredients: A good initial basis for the search space is constructed on the fine-level by using the interpolation of the coarse solution of the same eigenvalue problem in order to enhance the robustness of the algorithm. Also, an efficient and scalable two-level preconditioner based on the Schwarz framework is used for the correction equation. Some numerical examples obtained on a parallel cluster of computers are given in order to demonstrate the robustness and scalability of our PJD algorithm.
Authors:Frédéric Magoulès; Mark Parsons; Lorna Smith Pages: 1 - 2 Abstract: Publication date: September 2017 Source:Advances in Engineering Software, Volume 111 Author(s): Frédéric Magoulès, Mark Parsons, Lorna Smith
Authors:Maria Elena Innocenti; Alec Johnson; Stefano Markidis; Jorge Amaya; Jan Deca; Vyacheslav Olshevsky; Giovanni Lapenta Pages: 3 - 17 Abstract: Publication date: September 2017 Source:Advances in Engineering Software, Volume 111 Author(s): Maria Elena Innocenti, Alec Johnson, Stefano Markidis, Jorge Amaya, Jan Deca, Vyacheslav Olshevsky, Giovanni Lapenta Space weather is a rapidly growing field of science which studies processes occurring in the area of space between the Sun and the Earth. The development of space weather forecasting capabilities is a task of great societal relevance: space weather effects may damage a number of technological assets, among which power and communication lines, transformers, pipelines and the telecommunication infrastructure. Exascale computing is a fundamental ingredient for space weather forecasting tools based on physical, rather than statistical, models. We describe here our recent progresses towards a physics-based space weather forecasting tool with exascale computing. We select the semi-implicit, Particle In Cell, Implicit Moment Method implemented in the parallel, object-oriented, C++ iPic3D code as a promising starting point. We analyze the structure and the performances of the current version of the iPic3D code. We describe three algorithmic developments, the fully implicit method, the Multi-Level Multi-Domain method, and the fluid-kinetic method, which can help addressing the multiple spatial and temporal scales present in space weather simulations. We then examine, in a co-design approach, which requirements – vectorization, extreme parallelism and reduced communication – an application has to satisfy to fully exploit architectures such as GPUs and Xeon Phi’s. We address how to modify the iPic3D code to better satisfy these requirements. We then describe how to port the iPic3D code to the DEEP architecture currently under construction. The FP7 project DEEP (www.deep-project.eu) aims at building an exascale-ready machine composed of a cluster of Xeon nodes and of a collection of Xeon Phi coprocessors, used as boosters. The aim of the DEEP project is to enable exascale performance for codes, such as iPic3D, composed of parts which exhibit different potential for extreme scalability. Finally, we provide examples of simulations of space weather processes done with the current version of the iPic3D code.
Authors:Nick Brown Pages: 18 - 25 Abstract: Publication date: September 2017 Source:Advances in Engineering Software, Volume 111 Author(s): Nick Brown Whilst there have been great advances in HPC hardware and software in recent years, the languages and models that we use to program these machines have remained much more static. This is not from a lack of effort, but instead by virtue of the fact that the foundation that many programming languages are built on is not sufficient for the level of expressivity required for parallel work. The result is an implicit trade-off between programmability and performance which is made worse due to the fact that, whilst many scientific users are experts within their own fields, they are not HPC experts. Type oriented programming looks to address this by encoding the complexity of a language via the type system. Most of the language functionality is contained within a loosely coupled type library that can be flexibly used to control many aspects such as parallelism. Due to the high level nature of this approach there is much information available during compilation which can be used for optimisation and, in the absence of type information, the compiler can apply sensible default options thus supporting both the expert programmer and novice alike. We demonstrate that, at no performance or scalability penalty when running on up to 8196 cores of a Cray XE6 system, codes written in this type oriented manner provide improved programmability. The programmer is able to write simple, implicit parallel, HPC code at a high level and then explicitly tune by adding additional type information if required.
Authors:Florin Isaila; Javier Garcia; Jesus Carretero; Rob Ross; Dries Kimpe Pages: 26 - 31 Abstract: Publication date: September 2017 Source:Advances in Engineering Software, Volume 111 Author(s): Florin Isaila, Javier Garcia, Jesus Carretero, Rob Ross, Dries Kimpe The ever-increasing data needs of scientific and engineering applications require novel approaches to managing and exploring huge amounts of information in order to advance scientific discovery. In order to achieve this goal, one of the main priorities of the international scientific community is addressing the challenges of performing scientific computing on exascale machines within the next decade. Exascale platforms likely will be characterized by a three to four orders of magnitude increase in concurrency, a substantially larger storage capacity, and a deepening of the storage hierarchy. The current development model of independently applying optimizations at each layer of the system I/O software stack will not scale to the new levels of concurrency, storage hierarchy, and capacity. In this article we discuss the current development model for the I/O software stack of high-performance computing platforms. We identify the challenges of improving scalability, performance, energy efficiency, and resilience of the I/O software stack, while accessing a deepening hierarchy of volatile and nonvolatile storage. We advocate for radical new approaches to reforming the I/O software stack in order to advance toward exascale.
Authors:Abal-Kassim Cheik Ahamed; Frédéric Magoulès Pages: 32 - 42 Abstract: Publication date: September 2017 Source:Advances in Engineering Software, Volume 111 Author(s): Abal-Kassim Cheik Ahamed, Frédéric Magoulès Performance computations depend on the machine architecture, the operating system, the problem studied and obviously on the programming implementation. Solving partial differential equations by numerical methods such as the finite element method requires the solution of large sparse linear systems. Graphics processing unit (GPU) is now commonly used to accelerate numerical simulations and most supercomputers provide large number of GPUs to their users. This paper proposes a comparison of both CUDA and OpenCL GPU languages to take the highest performance of multi-GPUs clusters. We analyse, evaluate and compare their respective performances for computing linear algebra operations and for solving large sparse linear systems with the conjugate gradient iterative method on multi-GPUs clusters.
Authors:Alexander S. Minkin; Andrey A. Knizhnik; Boris V. Potapkin Pages: 43 - 51 Abstract: Publication date: September 2017 Source:Advances in Engineering Software, Volume 111 Author(s): Alexander S. Minkin, Andrey A. Knizhnik, Boris V. Potapkin We study the efficiency of OpenCL implementations for Tersoff and embedded-atom interatomic potentials. We show that Tersoff potential can be computed faster using atomic operations rather than using longer kernel code. On the contrary better performance can be gained for embedded-atom potential without atomic operations. Numerical force computation algorithm is the slowest but shows the best scaling with the highest GPU acceleration. The GPU acceleration of different algorithms was evaluated and compared to the serial implementations of similar algorithms. The performance of GPU implementations is superior to their serial counterparts and depends on the algorithm and arithmetic precision. The corresponding benchmarks and performance comparison were done using NVidia GPUs and Intel CPUs.
Authors:T.A. Puurtinen; J.I. Toivanen; K. Mattila; J. Hyväluoma; R.W. Nash; P.V. Coveney; J. Timonen Pages: 52 - 57 Abstract: Publication date: September 2017 Source:Advances in Engineering Software, Volume 111 Author(s): T.A. Puurtinen, J.I. Toivanen, K. Mattila, J. Hyväluoma, R.W. Nash, P.V. Coveney, J. Timonen The MPI intercommunication framework was used for coupling of two lattice-Boltzmann solvers with suspended particles, which model advection and diffusion respectively of these particles in a carrier fluid. Simulation domain was divided into two parts, one with advection and diffusion, and the other with diffusion only (no macroscopic flow). Particles were exchanged between these domains at their common boundary by a direct process to process communication. By analysing weak and strong scaling, it was shown that the linear scaling characteristics of the lattice-Boltzmann solvers were not compromised by their coupling.
Authors:Zhongwei Zhao; Haiqing Liu; Bing Liang Abstract: Publication date: Available online 20 July 2017 Source:Advances in Engineering Software Author(s): Zhongwei Zhao, Haiqing Liu, Bing Liang The joint bending and axial stiffness significantly influence the mechanical performance of lattice shell structures. However, most finite element models of the actual project established in the general finite element software are rigid or hinge-connected for simplicity. These characteristics are inconsistent with the actual situation and may lead to a large error. A novel numerical method was proposed in this paper to estimate the influence of joint stiffness, which includes bending and axial stiffness, on the mechanical behavior of lattice shell structures. This method can be used for inelastic analysis. First, the accuracy of the proposed element model was validated. The model was used to analyze lattice shell structures. The proposed element model can simultaneously consider semi-rigid joints and inelasticity with high accuracy, and it can be conveniently constructed in general finite element software.
Authors:A. Gariépy; H.Y. Miao; M. Lévesque Abstract: Publication date: Available online 18 July 2017 Source:Advances in Engineering Software Author(s): A. Gariépy, H.Y. Miao, M. Lévesque Shot peening is a surface treatment widely used to improve the fatigue performance of automotive and aerospace components. Beneficial compressive surface residual stress are introduced by projecting small, hard particles at high velocity onto a metallic part to plastically deform the surface. Shot types follow standardized size ranges and, in typical treatments, non-uniform impact velocities may also be encountered. In the current work, shot size and impact velocity distributions were evaluated and modelled for a specific industrial peening treatment with a sparse shot stream, using experimental data on shot and impact dimple sizes combined with finite element modelling and Monte Carlo simulations. The potential influence of impact velocity variability was assessed in terms of the residual stress state and surface roughness. For the process under study, depth of compressive residual stress was found to increase by 10% when accounting for non-uniform velocities, while the maximum compressive residual stress did not vary significantly. Furthermore, the advantages and limitations of omitting the lower-energy impacts to reduce the computational cost were evaluated.
Authors:Thomas Hacker; Shirley Dyke; Ali Irmak Ozdagli; Gemez Marshall; Christopher Thompson; Brian Rohler; Chul Min Yeum Abstract: Publication date: Available online 11 July 2017 Source:Advances in Engineering Software Author(s): Thomas Hacker, Shirley Dyke, Ali Irmak Ozdagli, Gemez Marshall, Christopher Thompson, Brian Rohler, Chul Min Yeum A select number of scientific communities have been quite successful in evolving the culture within their community to encourage publishing and to provide resources for re-using well-documented data. These data have great potential for analysis and knowledge generation beyond the purposes for which they were collected and intended. However, there are still barriers in this process. To explore this problem, we have developed a prototype tool: the Experiment Dashboard (ED), with the objective of demonstrating the ability and potential of enabling automated data ingestion from typical research laboratories. This innovative prototype was developed to create a novel system and artifact to explore the possibilities of allowing researchers in laboratories across the nation to link their data acquisition systems directly to structured data repositories for data and metadata ingestion. The prototype functions with commonly used data acquisition software at the data source and the HUBzero scientific gateway at the data sink. ED can be set up with minimal effort and expertise. In this paper, we describe the motivation and purposes for the prototype, the architecture we devised and functionality of this tool, and provide a demonstration of the tool for optical measurements in a structural engineering laboratory. The goal of this paper is to articulate and show through our prototype a vision for future cyberinfrastructure for empirical disciplines that rely on the rapid collection, analysis, and dissemination of valuable experimental data. We also discuss lessons learned that may be useful for others seeking to solve similar problems.
Authors:Weibin Yuan; Zhao Wang; Hao Chen; Kexing Fan Abstract: Publication date: Available online 10 July 2017 Source:Advances in Engineering Software Author(s): Weibin Yuan, Zhao Wang, Hao Chen, Kexing Fan Analysis of wind environment around integrated L-shaped buildings of different length-to-width ratios is carried out by using 2D and 3D numerical simulation methods. The Reynolds Stress Model is employed to examine the velocity distributions, surface pressures and vortex structures around the buildings for various different wind directions, in which the initial altitude of resonance region and shape coefficient are discussed in detail. The results show that the velocity along the central shaft is heavily affected by wind direction and the initial altitude of resonance region increases with increased length-to-width ratio. The vortex structure such as generating, evolution and shedding around the L-shape high-rise building under a 45° wind direction is also investigated. The shape coefficients predicted from the simulations are found to be consistent with those recommended in some national codes, although they are not fully considered in the current design codes.
Authors:Caiyan Deng; Yaru Niu; Baoming Gong; Yong Liu; Dongpo Wang Abstract: Publication date: Available online 8 July 2017 Source:Advances in Engineering Software Author(s): Caiyan Deng, Yaru Niu, Baoming Gong, Yong Liu, Dongpo Wang In the paper, the fatigue performances of as-welded T-joint and T-joint improved by high frequency mechanical impact (HFMI) were numerically investigated using structural hot spot stress approaches: linear surface extrapolation (LSE) and through thickness at the weld toe (TTWT). The effects of main plate thickness and material strength for HFMI-treated joints were investigated. The results showed that the TTWT method was more effective to study the effect of thickness on T-joints improved by HFMI treatment than LSE method. For as-welded T-joints, the thickness correction exponent n = 0.04 was obtained when the attachment plate thickness was set as constant. For HFMI-treated T-joints, a reverse thickness effect was observed with negative thickness correction exponents, and the thickness correction exponents increased with material strength. In addition, the adoption of S–N slope varying with yield strength was proven to be more proper for HFMI improvement assessment.
Authors:Bohumír Bastl; Marek Brandner; Jiří Egermaier; Kristýna Michálková; Eva Turnerová Abstract: Publication date: Available online 5 July 2017 Source:Advances in Engineering Software Author(s): Bohumír Bastl, Marek Brandner, Jiří Egermaier, Kristýna Michálková, Eva Turnerová This paper is focused on numerical solving of RANS (Reynolds-Averaged Navier-Stokes) equation with k − ω model for simulation of turbulent flows in 3D. The solver which is based on a recently proposed approach called isogeometric analysis is presented. This numerical method is based on isoparametric approach, i.e., the same basis functions are used for the description of a geometry of a computational domain and also for the representation of a solution. As computational domains are described by NURBS objects in isogeometric analysis, any real application requires to handle the so-called multipatch domains, where the computational domain is composed of more parts and each part is represented by one NURBS object. In our solver, discontinuous Galerkin method is used to connect different NURBS patches into one computational domain. The results of the solver are demonstrated on a standard benchmark example – backward facing step.
Authors:Vijay Kumar; Dinesh Kumar Abstract: Publication date: Available online 22 May 2017 Source:Advances in Engineering Software Author(s): Vijay Kumar, Dinesh Kumar In this paper, modified schemes are proposed for preventing a grey wolf optimizer (GWO) from premature exploration and convergence on optimization problems. Three novel strategies are developed to improve the performance of existing GWO. The first strategy uses the concept of prey weight. The second strategy uses the astrophysics concepts, which guide the grey wolves toward more promising areas of the search space. The beauty of this strategy is to let each grey wolf learn from not only movement of sun (symbolizes prey) in the search space but also the wolves are made to explore and exploit simultaneously. Third strategy combines the both, first and second strategies to take advantages of prey weight and astrophysics strategies. The proposed improvements in GWO have been evaluated on thirteen benchmark test functions. The performance of the proposed modifications has been compared with other five recently developed state-of-the-art techniques. The effects of scalability, noise, and control parameter have also been investigated. The statistical tests have been performed to validate the significance of modified variants. The proposed variants are also applied for seven well-known constrained engineering design problems. The experimental results depict the supremacy of the proposed modified algorithm in solving engineering design problems when compared with several existing techniques.
Authors:Wen-Zheng Xu; Chun Bao Li; Joonmo Choung; Jae-Myung Lee Abstract: Publication date: Available online 22 May 2017 Source:Advances in Engineering Software Author(s): Wen-Zheng Xu, Chun Bao Li, Joonmo Choung, Jae-Myung Lee Corrosion defects occur very often on the internal and external surfaces of pipelines, which may result in a serious threat to the integrity of the pipelines. Numerous studies investigated failure behavior of corroded pipelines with single corrosion defects. However, few studies focus on interacting corrosion defects. Interacting defects are defined as defects with certain proximity that interact to reduce the overall strength of a pipeline. In the present study, the failure behavior of pipelines with interacting corrosion defects was studied using a finite element method, and then a solution was proposed to predict burst pressure using an artificial neural network. The solution was validated by experimental results in previous studies and compared with other existing assessment solutions to prove its applicability and efficiency.
Authors:Dongkyu Lee; Jaehong Lee; Quoc Hoan Doan Abstract: Publication date: Available online 25 April 2017 Source:Advances in Engineering Software Author(s): Dongkyu Lee, Jaehong Lee, Quoc Hoan Doan This research proposes the inelastic buckling and modal analysis to design optimal shape and size through UL700 steel arch-grid unit module which is for localized reinforcement of soft ground. The optimal arch-grid design is achieved among its most efficient design possibilities such as different plate type, extended grid, multi-story grid, combined grid. The steel arch-grid unit module is composed of a vertical member and a board member combined with the top and bottom sides of the said vertical member, including the horizontal member equipped with multiple arm parts combined with the center part into one body in the shape of a cross. The construction method for reinforcement of soft ground is proposed in detail in this research. Numerical experiments are provided to survey optimal shape and size of arch-grid structures with differential models applied to buckling analysis, modal and static load, in consideration of both linear and nonlinear behaviors, by using SAP2000 version 15.0.1 software. With sufficient features of steel arch-grid for supporting structural foundations, this research suggests the possibility of requiring more studies and of providing more applications in the field of constructional structures.
Authors:Boqing Gao; Chuanzhong Hao; Tierui Li; Jun Ye Abstract: Publication date: Available online 24 April 2017 Source:Advances in Engineering Software Author(s): Boqing Gao, Chuanzhong Hao, Tierui Li, Jun Ye Automatic grid generation on a curved surface is important to more efficient design of free-form structures. However, it is neither a convenient nor an obvious task for engineers to create a discrete grid structure on a complex surface that meets the architectural requirements. Besides, research on the rapid grid generation methodology for free form structural design is still limited. In order to achieve better grid distribution of rods on free-form surface, a grid generation methodology which combines surface flattening technique with guide line method is put forward. The parametric domain of the free-form surface was firstly divided into a number of parts and a discrete free-form surface was accordingly formed by mapping the generated dividing points onto the curved surface. The free-form surface was then flattened based on the principle of identical area. Accordingly, the flattened rectangular lattices were fitted into the 2D surface where grids were formed by using the guide line method. Finally, the 2D grids were mapped onto the 3D surface, and grids were therefore generated on the given surface. A grid shape and rod length quality index was proposed to evaluate the shape of grid cells and rod lengths. The results show that the grid shape quality index and the deviation of rod length of the grid structure are reduced by up to 47% and 34% respectively by using the guide line method with surface flattening when compared to the method without surface flattening.
Authors:A. Kaveh; A. Dadras Abstract: Publication date: Available online 18 April 2017 Source:Advances in Engineering Software Author(s): A. Kaveh, A. Dadras This paper introduces a new optimization algorithm based on Newton's law of cooling, which will be called Thermal Exchange Optimization algorithm. Newton's law of cooling states that the rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings. Here, each agent is considered as a cooling object and by associating another agent as environment, a heat transferring and thermal exchange happens between them. The new temperature of the object is considered as its next position in search space. The performance of the algorithm is examined by some mathematical functions and four mechanical benchmark problems.
Authors:Qi Zhou; Yang Yang; Ping Jiang; Xinyu Shao; Longchao Cao; Jiexiang Hu; Zhongmei Gao; Chaochao Wang Abstract: Publication date: Available online 18 April 2017 Source:Advances in Engineering Software Author(s): Qi Zhou, Yang Yang, Ping Jiang, Xinyu Shao, Longchao Cao, Jiexiang Hu, Zhongmei Gao, Chaochao Wang Selecting reasonable laser beam welding (LBW) process parameters is very helpful for obtaining a good welding bead profile and hence a high quality of the welding joint. Existing process parameter optimization approaches for LBW either based on cost-expensive physical experiments or low-fidelity (LF) computer simulations. This paper proposes a multi-fidelity (MF) metamodel based LBW process parameter optimization approach, in which different levels fidelity information, both from LF computer simulations and high-fidelity (HF) physical experiments can be integrated and fully exploited. In the proposed approach, a three-dimensional thermal finite element model is developed as the LF model, which is fitted with a LF metamodel firstly. Then, by taking the LF metamodel as a base model and scaling it using the HF physical experiments, a MF metamodel is constructed to approximate the relationships between the LBW process parameters and the bead profile. Two metrics are adopted to compare the prediction accuracy of the MF metamodel with the single-fidelity metamodels solely constructed with physical experiments or computer simulations. Results illustrate that the MF metamodel outperforms the single-fidelity metamodels both in global and local accuracy. Finally, the fast elitist non-dominated sorting genetic algorithm (NSGA-II) is used to facilitate LBW process parameter space exploration and multi-objective Pareto optima search. LBW verification experiments verify the effectiveness and reliability of the obtained optimal process parameters.
Authors:Pavel Kůs; Jakub Šístek Abstract: Publication date: Available online 7 April 2017 Source:Advances in Engineering Software Author(s): Pavel Kůs, Jakub Šístek We study the effect of adaptive mesh refinement on a parallel domain decomposition solver of a linear system of algebraic equations. These concepts need to be combined within a parallel adaptive finite element software. A prototype implementation is presented for this purpose. It uses adaptive mesh refinement with one level of hanging nodes. Two and three-level versions of the Balancing Domain Decomposition based on Constraints (BDDC) method are used to solve the arising system of algebraic equations. The basic concepts are recalled and components necessary for the combination are studied in detail. Of particular interest is the effect of disconnected subdomains, a typical output of the employed mesh partitioning based on space-filling curves, on the convergence and solution time of the BDDC method. It is demonstrated using a large set of experiments that while both refined meshes and disconnected subdomains have a negative effect on the convergence of BDDC, the number of iterations remains acceptable. In addition, scalability of the three-level BDDC solver remains good on up to a few thousands of processor cores. The largest presented problem using adaptive mesh refinement has over 109 unknowns and is solved on 2048 cores.
Authors:Hugo Aliaga-Aguilar; Cristina Cuerno-Rejado Abstract: Publication date: Available online 6 April 2017 Source:Advances in Engineering Software Author(s): Hugo Aliaga-Aguilar, Cristina Cuerno-Rejado There is a high demand for small unmanned aircraft for a wide variety of missions. The relatively limited experience and resources of new commercial companies renders it almost impossible for them to tackle a complete design process with the same quality and results as bigger and more experienced companies. We aim to develop a full rapid design methodology software for such aircraft and present the first step in the process in the form of a performance estimation model. This model is tested with data from ten different commercially available RPAS, as well as two additional RPAS for aerodynamic validation. A comparison between the results obtained by means of this model and the manufacturers’ data is presented.
Authors:Anirban Sengupta; Dipanjan Roy Abstract: Publication date: Available online 4 April 2017 Source:Advances in Engineering Software Author(s): Anirban Sengupta, Dipanjan Roy This paper presents a novel low cost scheduling driven watermarking methodology for modern computer aided design (CAD) high level synthesis tools. The proposed watermarking algorithm is embedded in the scheduling module of a CAD high level synthesis (HLS) tool. The presented watermarking methodology is capable of reusable intellectual property (IP) core protection of control data flow graphs (CDFG) from a vendor's perspective based on user provided resource constraint and loop unrolling factor as inputs. The proposed low cost robust watermarking embedded inside high level synthesis process protects an IP core against threats such as false claim of ownership and piracy. The proposed watermarking satisfies desirable properties such as covertness, robustness, low embedding cost and low complexity. Results of comparison indicated significant reduction in embedding cost through proposed technique than similar state of the art techniques.
Authors:Saeed K. Babanajad; Amir H. Gandomi; Amir H. Alavi Abstract: Publication date: Available online 4 April 2017 Source:Advances in Engineering Software Author(s): Saeed K. Babanajad, Amir H. Gandomi, Amir H. Alavi The complexity associated with the in-homogeneous nature of concrete suggests the necessity of conducting more in-depth behavioral analysis of this material in terms of different loading configurations. Distinctive feature of Gene Expression Programming (GEP) has been employed to derive computer-aided prediction models for the multiaxial strength of concrete under true-triaxial loading. The proposed models correlate the concrete true-triaxial strength (σ1) to mix design parameters and principal stresses (σ2,σ3), needless of conducting any time-consuming laboratory experiments. A comprehensive true-triaxial database is obtained from the literature to build the proposed models, subsequently implemented for the verification purposes. External validations as well as sensitivity analysis are further carried out using several statistical criteria recommended by researchers. More, they demonstrate superior performance to the other existing empirical and analytical models. The proposed design equations can readily be used for pre-design purposes or may be used as a fast check on deterministic solutions.
Authors:Jae Hyuk Lim; Hobeom Kim; Sun-Won Kim; Dongwoo Sohn Abstract: Publication date: Available online 22 March 2017 Source:Advances in Engineering Software Author(s): Jae Hyuk Lim, Hobeom Kim, Sun-Won Kim, Dongwoo Sohn A simple and accurate scheme for modeling microstructures is proposed with the help of element trimming combined with signed distance function based boundary smoothing. To accommodate randomly distributed fibers in unidirectional composites, digital image processing is used. The interfaces of multi-materials are identified by introducing a signed distance function, and then, square background elements crossing the interfaces are simply trimmed and divided to represent a single material behavior by a single element. After element trimming, the elements that are polygon-shaped in the two-dimensional domain are split into conventional three-node triangle elements (six-node prism elements in the three-dimensional domain) available in many commercial software packages. The present modeling scheme was verified through benchmark examples in terms of the accuracy and efficiency and then applied to the modeling of unidirectional composites based on real microscopic images to evaluate the equivalent elastic properties.
Authors:Adam J. Sadowski; O. Kunle Fajuyitan; Jie Wang Abstract: Publication date: Available online 18 March 2017 Source:Advances in Engineering Software Author(s): Adam J. Sadowski, O. Kunle Fajuyitan, Jie Wang The new Reference Resistance Design (RRD) method, recently developed by Rotter [1], for the manual dimensioning of metal shell structures effectively permits an analyst working with only a calculator or spreadsheet to take full advantage of the realism and accuracy of an advanced nonlinear finite element (FE) calculation. The method achieves this by reformulating the outcomes of a vast programme of parametric FE calculations in terms of six algebraic parameters and two resistances, each representing a physical aspect of the shell's behaviour. The formidable challenge now is to establish these parameters and resistances for the most important shell geometries and load cases. The systems that have received by far the most research attention for RRD are that of a cylindrical shell under uniform axial compression and uniform bending. Their partial algebraic characterisations required thousands of finite element calculations to be performed across a four-dimensional parameter hyperspace (i.e. length, radius to thickness ratio, imperfection amplitude, linear strain hardening modulus). Handling so many nonlinear finite element models is time-consuming and the quantities of data generated can be overwhelming. This paper illustrates a computational strategy to deal with both issues that may help researchers establish sets of RRD parameters for other important shell systems with greater confidence and accuracy. The methodology involves full automation of model generation, submission, termination and processing with object-oriented scripting, illustrated using code and pseudocode fragments.
Authors:Ahmed Kovacevic; Sham Rane Abstract: Publication date: Available online 11 March 2017 Source:Advances in Engineering Software Author(s): Ahmed Kovacevic, Sham Rane Algebraic procedures are available to generate computational grid for CFD analysis of twin screw compressors. Recently new algebraic method was formulated to generate numerical grids for CFD calculation of twin screw machines with grids generated from outer casing boundaries [16,18]. In this paper, the grids of Rotor to Casing and Casing to Rotor type are tested for performance calculation of a dry air screw compressor using ANSYS CFX solver and the results have been compared with measurements. Firstly the base-line grid of the Rotor to Casing grid type was used to obtain CFD results. A grid independent solution was obtained for this base-line grid. The size of the mesh thus obtained has been used with other grid variants for comparison. A set of successively refined Casing to Rotor grid type was tested by increasing the density of nodes on the rotor profile in the interlobe leakage region. A gradual improvement in the accuracy of flow prediction was achieved with successive refinement in the interlobe region. The third variant used for comparison is a Casing to Rotor grid type with a single rotor domain that has no interface between the rotor blocks. A significant improvement in the prediction of flow and internal pressure was achieved. These developments have also extended the capability of the deforming grids to be used with other CFD solvers like STAR-CCM+ and ANSYS FLUENT. Due to fully hexahedral cell structure and improved global grid quality, addition of physical phenomena like oil injection in the models has now become achievable.
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