N-independent Localized Krylov–Bogoliubov-de Gennes Method: Ultra-fast Numerical Approach to Large-scale Inhomogeneous Superconductors

Abstract. A numerical approach is substantiated for searching for the large-scale alpha-like instability in thermoconvective turbulence. The main idea of the search strategy is the application of a forcing function which can have a physical interpretation. The forcing simulates the influence of small-scale helical turbulence generated in a rotating fluid with internal heat sources and is applied to naturally induced fully developed convective flows. The strategy is tested using the Rayleigh-Bénard convection in an extended horizontal layer of incompressible fluid heated from below. The most important finding is an enlargement of the typical horizontal scale of the forming helical convective structures accompanied by a cells merging, an essential increase in the kinetic energy of flows and intensification of heat transfer. The results of modeling allow explaining how the helical feedback can work providing the non-zero mean helicity generation and the mutual intensification of horizontal and vertical circulation, and demonstrate how the energy of the additional helical source can be effectively converted into the energy of intensive large-scale vortex flow.

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Performance Prediction and Optimization of Low Pressure Steam Turbine Radial Diffuser at Design and Off-Design Conditions Using Streamline Curvature Method

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4035527 ◽

2017 ◽

Vol 139 (7) ◽

Author(s):

Luying Zhang ◽

Francesco Congiu ◽

Xiaopeng Gan ◽

David Karunakara

Keyword(s):

Steam Turbine ◽

Flow Separation ◽

Large Scale ◽

Current Method ◽

Low Pressure ◽

Numerical Approach ◽

Optimization Process ◽

Exhaust Hood ◽

Streamline Curvature ◽

Wide Range

The performance of the radial diffuser of a low pressure (LP) steam turbine is important to the power output of the turbine. A reliable and robust prediction and optimization tool is desirable in industry for preliminary design and performance evaluation. This is particularly critical during the tendering phase of retrofit projects, which typically cover a wide range of original equipment manufacturer and other original equipment manufacturers designs. This work describes a fast and reliable numerical approach for the simulation of flow in the last stage and radial diffuser coupled with the exhaust hood. The numerical solver is based on a streamline curvature throughflow method and a geometry-modification treatment has been developed for off-design conditions, at which large-scale flow separation may occur in the diffuser domain causing convergence difficulty. To take into account the effect of tip leakage jet flow, a boundary layer solver is coupled with the throughflow calculation to predict flow separation on the diffuser lip. The performance of the downstream exhaust hood is modeled by a hood loss model (HLM) that accounts for various loss generations along the flow paths. Furthermore, the solver is implemented in an optimization process. Both the diffuser lip and hub profiles can be quickly optimized, together or separately, to improve the design in the early tender phase. 3D computational fluid dynamics (CFD) simulations are used to validate the solver and the optimization process. The results show that the current method predicts the diffuser/exhaust hood performance within good agreement with the CFD calculation and the optimized diffuser profile improves the diffuser recovery over the datum design. The tool provides General Electric the capability to rapidly optimize and customize retrofit diffusers for each customer considering different constraints.

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Solving PDEs with radial basis functions

Acta Numerica ◽

10.1017/s0962492914000130 ◽

2015 ◽

Vol 24 ◽

pp. 215-258 ◽

Cited By ~ 108

Author(s):

Bengt Fornberg ◽

Natasha Flyer

Keyword(s):

Radial Basis Functions ◽

Finite Differences ◽

Large Scale ◽

Numerical Approach ◽

Basis Functions ◽

Integration Time ◽

Small Scale ◽

Major Step ◽

Mesh Free ◽

Radial Basis

Finite differences provided the first numerical approach that permitted large-scale simulations in many applications areas, such as geophysical fluid dynamics. As accuracy and integration time requirements gradually increased, the focus shifted from finite differences to a variety of different spectral methods. During the last few years, radial basis functions, in particular in their ‘local’ RBF-FD form, have taken the major step from being mostly a curiosity approach for small-scale PDE ‘toy problems’ to becoming a major contender also for very large simulations on advanced distributed memory computer systems. Being entirely mesh-free, RBF-FD discretizations are also particularly easy to implement, even when local refinements are needed. This article gives some background to this development, and highlights some recent results.

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Computing CHEMKIN Sensitivities Using Complex Variables

Part A: Combustion and Alternative Energy Technology; Computers in Engineering; Drilling Technology; Environmental Engineering Technology; Composite Materials Design and Analysis; Manufacturing and Services ◽

10.1115/etce2001-17013 ◽

2001 ◽

Author(s):

Nelson Butuk ◽

JeanPaul Pemba

Keyword(s):

Finite Difference ◽

Large Scale ◽

Jacobian Matrix ◽

Numerical Approach ◽

Chemical Mechanism ◽

Step Size ◽

Large Scale Problems ◽

Low Dimensional ◽

Elementary Chemical ◽

Finite Difference Approach

Abstract This paper discusses an accurate numerical approach of computing the Jacobian Matrix for the calculation of low dimensional manifolds for kinetic chemical mechanism reduction. The approach is suitable for numerical computations of large scale problems and is more accurate than the finite difference approach of computing Jacobians. The method is demonstrated via a highly stiff reaction mechanism for the synthesis of Bromide acid and a H2/Air mechanism using a modified CHEMKIN package. The Bromide mechanism consisted of five species participating in six elementary chemical reactions and the H2/Air mechanism consisted of 11 species and 23 reactions. In both cases it is shown that the method is superior to the finite difference approach of computing derivatives with an arbitrary computational step size, h.

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Human Mobility Patterns at the Smallest Scales

Communications in Computational Physics ◽

10.4208/cicp.120614.190115a ◽

2015 ◽

Vol 18 (2) ◽

pp. 417-428 ◽

Cited By ~ 3

Author(s):

Pedro G. Lind ◽

Adriano Moreira

Keyword(s):

Large Scale ◽

Spatial Scales ◽

Human Mobility ◽

Numerical Approach ◽

Human Motion ◽

Mobile Phone Data ◽

Data Sets ◽

Mobility Patterns ◽

Access Points ◽

Dollar Bill

AbstractWe present a study on human mobility at small spatial scales. Differently from large scale mobility, recently studied through dollar-bill tracking and mobile phone data sets within one big country or continent, we report Brownian features of human mobility at smaller scales. In particular, the scaling exponents found at the smallest scales is typically close to one-half, differently from the larger values for the exponent characterizing mobility at larger scales. We carefully analyze 12-month data of the Eduroam database within the Portuguese university of Minho. A full procedure is introduced with the aim of properly characterizing the human mobility within the network of access points composing the wireless system of the university. In particular, measures of flux are introduced for estimating a distance between access points. This distance is typically non-Euclidean, since the spatial constraints at such small scales distort the continuum space on which human mobility occurs. Since two different exponents are found depending on the scale human motion takes place, we raise the question at which scale the transition from Brownian to non-Brownian motion takes place. In this context, we discuss how the numerical approach can be extended to larger scales, using the full Eduroam in Europe and in Asia, for uncovering the transition between both dynamical regimes.

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Limit Loads for Structural Elements Made of Heterogeneous Materials

Volume 3: Design and Analysis ◽

10.1115/pvp2012-78308 ◽

2012 ◽

Author(s):

Min Chen ◽

Abdelkader Hachemi ◽

Dieter Weichert

Keyword(s):

Material Properties ◽

Large Scale ◽

Numerical Approach ◽

Interior Point Algorithm ◽

Structural Elements ◽

Finite Element Discretization ◽

Element Discretization ◽

Limit Loads ◽

Heterogeneous Structures ◽

Conforming Finite Element

A numerical method is presented for determining the limit loads of periodically heterogeneous structures subjected to variable loads. The Melan’s lower-bound shakedown theorem was applied to representative volume elements. Combined with the homogenization technique, the homogenized material properties were determined through transformation from the mesoscopic to macroscopic admissible loading domains. For the numerical applications, solid non-conforming finite element discretization and large-scale nonlinear optimization, based on an interior-point-algorithm were used. The methodology is illustrated by the application to pipes models. This way, the proposed method provides a direct numerical approach to evaluate the macroscopic strength of heterogeneous structures with periodic micro- or meso-structure as a useful tool for the design of structures.

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LARGE SCALE SIMULATION OF WAVE PROPAGATION IN SOILS INTERACTING WITH STRUCTURES USING FEM AND SBFEM

Journal of Computational Acoustics ◽

10.1142/s0218396x11004316 ◽

2011 ◽

Vol 19 (01) ◽

pp. 75-93 ◽

Cited By ~ 10

Author(s):

MARCO SCHAUER ◽

SABINE LANGER ◽

JOSE E. ROMAN ◽

ENRIQUE S. QUINTANA-ORTÍ

Keyword(s):

Wave Propagation ◽

Soil Structure ◽

Large Scale ◽

Dynamical Behavior ◽

Radiation Condition ◽

Numerical Approach ◽

Soil Structure Interaction ◽

Crucial Point ◽

Large Scale Problems ◽

Energy Plants

This paper applies a parallel algorithm for a coupled Finite Element/Scaled Boundary Element (FEM/SBFEM)-approach to study soil-structure-interaction problems. The application code is designed to run on clusters of computers, and it enables the analysis of large-scale problems. A crucial point of the approach is that the SBFEM fulfills the radiation condition. Hence, the hybrid numerical approach is well suited for such problems where wave propagation to infinity in an unbounded domain must be considered. The main focus of the paper is to show the applicability of the numerical implementation on large scale problems. First the coupled FEM/SBFEM approach is validated by comparing the numerical results with a semi-analytical solution for a settlement problem. Then the implemented algorithm is applied to study the dynamical behavior of founded wind energy plants under time dependent loading.

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A new circular spinneret system for electrospinning numerical approach and electric field optimization

Thermal Science ◽

10.2298/tsci1904229z ◽

2019 ◽

Vol 23 (4) ◽

pp. 2229-2235 ◽

Cited By ~ 1

Author(s):

Ziming Zhu ◽

Han Wang ◽

Guojie Xu ◽

Rouxi Chen ◽

Lixiong Huang ◽

...

Keyword(s):

Tissue Engineering ◽

Finite Element ◽

Electric Field ◽

Large Scale ◽

Energy Harvester ◽

Wearable Sensors ◽

Element Model ◽

Numerical Approach ◽

Electrospinning Process ◽

Effective Technique

Electrospinning is believed to be the most effective technique to produce microfibers or nanofibers at large scale, which can be applied in various hightech areas, including energy harvester, tissue engineering, and wearable sensors. To enhance nanofiber throughput during a multi-needle electrospinning process, it is an effective way to keep the electric field uniform by optimizing electrospinning spinnerets. For this purpose, a novel circular spinneret system is designed and optimized numerically by a 3-D finite element model, the optimal collector shape is also obtained.

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Energy Efficiency of a Vernacular Building Design and Materials in Hot Arid Climate: Experimental and Numerical Approach

International Journal of Renewable Energy Development ◽

10.14710/ijred.2021.35310 ◽

2021 ◽

Vol 10 (3) ◽

pp. 481-494

Author(s):

Karima El Azhary ◽

Mohamed Ouakarrouch ◽

Najma Laaroussi ◽

Mohammed Garoum

Keyword(s):

Thermal Comfort ◽

Energy Efficient ◽

Large Scale ◽

Research Study ◽

Experimental Testing ◽

Vernacular Architecture ◽

Weather Conditions ◽

Building Design ◽

Numerical Approach ◽

Coating Materials

Morocco faces tremendous climate constraints; the climate is hot and dry in most parts of the country, and when selecting an energy-saving approach, the architectural landscape becomes essential.Designer and building professionals seem to have neglected this large-scale integration. Sustainable development programs in terms of sustainable architecture are ongoing in countries around the world. One part of this trend is the growing concern shown in the high environmental efficiency of vernacular architecture. It is within this prescriptive framework that this research study is being conducted, which reveals novel architectural style integrating thermal comfort, energy efficient characteristics, passive solar elements architecture, and construction techniques inspired from the vernacular Ksourian architectural configurations. The goal of the present research study is to identify features of energy efficient vernacular architecture and thermal performances that affect indoor thermal comfort conditions for adaptation to current lifestyles in modern architecture. The key characteristics developed are; built mass structure, building orientation, space planning, availability of s, building techniques, and new coating materials for manufacturing and roofing. The suggested methodology enables to analyze the thermal performance analysis, applying an experimental research using experimental testing measurement and comparative optimization processes for thermal efficiency and comfort evaluation of a traditional vernacular earthen house.Series of experimental thermophysical characterization measurements have been carried out in order to quantify on a real scale the thermophysical properties that characterize the Rissani earth. Thusthermophysical characterization results are operated as input data for the thermal dynamic simulation for the purpose to evaluate thermal performances and comfort under the weather conditions and control natural comfort in both summer and winter, without using heating or cooling systems. Ultimately, the simulations carried out make it possible to identify the optimal orientation, revealing an effective decrease in interior temperatures during summer and providing good thermal comfort in winter.

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A numerical investigation of the statistical size effect in non-crimp fabric laminates under homogeneous compressive loads

Journal of Composite Materials ◽

10.1177/00219983211057346 ◽

2021 ◽

pp. 002199832110573

Author(s):

Benedikt Daum ◽

Gerrit Gottlieb ◽

Nabeel Safdar ◽

Martin Brod ◽

Jan-Hendrik Ohlendorf ◽

...

Keyword(s):

Compressive Strength ◽

Large Scale ◽

Fiber Material ◽

Strength Loss ◽

Numerical Approach ◽

Strength Increase ◽

Present Contribution ◽

Data Set ◽

Weakest Link ◽

Weibull Theory

The compressive strength of fiber reinforced composites is typically limited by a shear localization phenomenon known as microbuckling and is very sensitive to local imperfections of fiber alignment. Local misalignments act as randomly distributed flaws and introduce a dependence of the compressive strength on the size of material volume element under consideration. For homogeneously loaded material elements, weakest-link theory in combination with a Weibull power law is a frequently employed statistical model for microbuckling strength. This implies a dependence of strength on the size of volume under consideration. The present contribution investigates the strength–size relation for a non-crimp fabric via a numerical approach. Characteristics of the misalignment flaws used in simulations are derived from a comprehensive data set collected via large-scale measurements of roving dislocations on dry fiber material. Predictions resulting from the weakest-link Weibull theory are compared against strength–size statistics gathered by numerical analysis. In this manner, the size effects in single plies and laminates are quantified. The main findings are that weakest-link Weibull theory is well suited to predict size related strength loss in individual plies. However, it is also found that when plies are bonded to form laminates, misalignments in individual plies are mitigated in a way that is inconsistent with the weakest-link assumption. In all situations considered here, the strength loss expected from weakest-link Weibull theory was outweighed by a strength increase due to the mitigation effect when the volume was increased by adding extra layers to a laminate.

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