Commercial Numerical Software Research Articles

A methodology for control and design of required ground reinforcement measures regarding train-induced ground vibrations

A user-friendly methodology for efficient non-linear numerical calculations of train-induced ground vibrations in railway embankments has been developed. This was achieved by creating an input file for setting up the problem and a shell program that reads the input file, set-ups, and runs the model of the problem on commercial numerical software, and also extracts the results from the calculations to an output file. Through this, the calculations can be automated and thus become easy to use. In addition, much effort has been put into optimizing the calculations for the computational time while maintaining sufficient accuracy. A key part of the developed methodology is that it includes an efficient way to consider that the soil properties are shear strain dependent. This was achieved using the so-called equivalent linear method and by superposition of the calculated shear strain adjusted linear elastic deformations for a single moving load. The developed methodology has, with good agreement, been verified against a case history with vibrations measurements both before and after ground reinforcement measures consisting of lime-cement columns. The presented methodology, called base-model methodology, can identify the risk for large ground vibrations for planned new and existing railway embankments and design required ground reinforcement measures based on permissible vibration requirements.

Pressure Transient Behaviors of Discretely Fractured Reservoirs Using a Numerical Discrete Fracture Model

Summary The conventional dual-porosity model (Warren and Root 1963) may not apply to naturally fractured reservoirs (NFRs), which have poorly connected fractures. To narrow this gap, a new discrete fracture model (DFM)-based numerical well-testing model is developed for pressure transient analysis in vertical wells interacting with natural fractures (NFs). The numerical model is based on a DFM and unstructured perpendicular bisector (PEBI) grid system. The accuracy and practicality of the proposed model have been demonstrated by model verifications with a commercial numerical software. The results show that the flow regimes of the vertical well interacting with NFs can be divided into wellbore storage and skin effects, bilinear flow, linear flow, radial flow, NF effect, and boundary-dominated flow. This is the radial flow of the formation before pressure propagates to NFs, which is virtually quite different from that in the conventional dual-porosity model. However, there are no bilinear and linear flow stages in the vertical well interacting with no NFs. It is found that the vertical well interacting with NFs has a lower pressure depletion. It is also found that the “V-shape” caused by the NF effect in the pressure derivative curve becomes deeper when there are more NFs, longer NFs, and higher fracture conductivity. Furthermore, the “V-shape” appears earlier, and the duration of the NF effect is longer as the number of NFs increases. Besides, with the decrease of the distance between the fracture and the well, the impacts of NFs on pressure transient behaviors of the vertical well are more significant. This work provides a meaningful way to understand the pressure transient behaviors of discrete NFs.

Active control of nonlinear coupled transient vibrations of multifunctional sandwich plates with agglomerated FG-CNTs core/magneto-electro-elastic facesheets

This article investigates the controlled nonlinear transient response of sandwich plates made of magneto-electro-elastic (MEE) facesheets and agglomerated carbon nanotube (ACNT) core. The control is achieved by active constrained layer damping (ACLD) treatment which consists of piezoelectric (PE) and viscoelastic (VE) layers. The agglomeration is mathematically modelled using the Eshelby–Mori–Tanaka approach. The governing equations are derived under the framework of finite element (FE) methods using Hamilton’s principle and condensation technique. The VE patch of the ACLD treatment is modelled through the Golla–Hughes–McTavish method. This evaluation has considered two states of agglomerations, such as complete and partial agglomeration. The proposed FE model facilitates the integration of the three-field (magnetic, electric and elastic) coupling with the agglomeration and electromagnetic circuit effects, which makes this work interesting. It acts as a ready tool for the realistic design of a smart structure and system. In addition, the computational efforts and efficiency of the proposed FE model prove to be better than the commercial numerical software. Extensive numerical examples are solved to assess the influence of CNT distributions, electromagnetic circuits, coupling, mechanical boundary conditions, thickness configuration and ACLD patch position. This work serves as a novel benchmark solution for further research on the active control of agglomerated CNT structures.

3D Modelling of Excavation-Induced Anisotropic Responses of Deep Drifts at the Meuse/Haute-Marne URL

Understanding the excavation-induced fractured zone (EFZ) around drifts is paramount in the context of the deep geological disposal for nuclear waste since fractures can introduce pathways for the migration of radionuclides. Drifts in the Meuse/Haute-Marne Underground Research Laboratory (URL) have been essentially excavated following the two main directions of major and minor horizontal stresses. Field observations on the two drifts GCS (parallel to major horizontal stress direction) and GED (parallel to minor horizontal stress direction) in the URL show anisotropic shapes of EFZ around drifts through both orientations and anisotropic convergences. These anisotropic responses resulted from the inherent and/or induced anisotropies of the host rock as well as the anisotropic stress field. This study focuses on 3D numerical modelling of excavation-induced anisotropic responses including shape and extent of EFZ, and short-term convergences of drifts. The main assumption is that the failure of claystone material is due to fracturing along weakness planes (ubiquitous joints) and the failure of the rock matrix. The ubiquitous joint failure is represented by perfectly plastic models for both tensile and shear yield functions. Their orientation is determined from the stress state based on the fracture mechanics, which includes tensile, longitudinal splitting and shear (conjugate planes) cracks. The rock matrix is assumed to be elastoplastic with hardening, softening and residual behaviours. Confining pressure dependency for the post-peak behaviour with a brittle–ductile transition is taken into account for the rock matrix. The proposed model is implemented into a commercial numerical software FLAC3D. The main features of the implemented model are shown by the simulation of laboratory triaxial compression tests, as well as field observation within the URL. In particular, comparisons between 3D simulations of GCS and GED drifts with in situ observations shows promising results, which demonstrates advances of present model with respect to existing models.

Pressure transient analysis of a multi-horizontal-well pad by a semi-analytical model: Methodology and case study

Drilling more infill multi-fractured horizontal wells (MFHWs) is one of the most direct oil and gas production methods in unconventional reservoirs with high recovery. MFHWs in the multi-horizontal-well pad can be easily interfered by the adjacent wells during well testing. Unfortunately, most of the existing well testing models for MFHWs are limited to a single well. A semi-analytical well testing model for transient pressure analysis in a multi-horizontal-well pad is presented in this work. In the proposed model, the entire formation is divided into three domains, namely matrix, natural fracture, and hydraulic fracture, to describe unconventional reservoirs comprehensively. With Laplace transform and Stehfest numerical inversion techniques, the reservoir models with matrix and natural fracture systems are solved analytically. The solutions of the hydraulic fracture model for multiple MFHWs are obtained by the finite difference method. The pressure superposition method and production rate relationship are used to characterize the impact from the adjacent wells. The general solutions of the multi-well reservoir model and hydraulic fracture model are then coupled to obtain the tested well's bottom-hole pressure. The results of the proposed model are in good agreement with the commercial numerical software. The multi-horizontal-well pad's integrated flow regimes can be divided into a bilinear flow, linear formation flow, the pseudo radial flow of hydraulic fracture, multi-MFHW effect, cross-flow between matrix and natural fracture, and formation pseudo radial flow. The pseudo radial flow of hydraulic fracture, the multi-MFHW effect, cross flow, and formation pseudo radial flow have unique characteristics in the multi-horizontal-well pad, and these flow regimes are highly affected by the adjacent MFHWs properties and well-spacing. With the change of well-spacing, the multi-MFHW effect is characterized by the linear flow inside the multi-horizontal-well pad or the multi-well pad's biradial flow. The comparison of pseudo-steady-state (PSS) flow and transient flow indicates that different cross-flow conditions from the matrix to natural fracture will only affect the derivative curve's cross-flow behavior. The case study shows that the proposed model can obtain a more accurate interpretation result of the tested well under the adjacent well's effect.

Generalised Component Method-based finite element analysis of steel frames

The design-by-analysis approach lays the foundation for the next generation of structural design standards in which the strength and structural safety check are performed in a single step at system level, without recourse to a structural standard for individual member checks. However, to date, no attempt has been made towards considering the failure of joints in the structural analysis, without which the complete set of limit states cannot be accurately predicted. This paper presents a new analysis approach that incorporates macro-element joint models based on the Generalised Component Method in the FE analysis of steel frame buildings. The new analysis approach is termed Generalised Component Method-based finite-element (GCM-FE) analysis. The fundamental aspects and principles of the GCM-FE analysis approach are established in this paper, including the framework of GCM-FE analysis, the constitutive models for the connection components and the implementation of GCM-FE analysis in commercial numerical software including an automatic modelling technique. The GCM-FE joint modelling method is first validated against the experimental results of three steel beam-to-column connection types, including the bolted moment end-plate connection, top-and-seat angle connection and web angle connection. GCM-FE analysis is subsequently performed on a two-storey four-bay irregular steel frame, showing apparent advantages over the traditional analysis methods which adopt simplified joint models. The GCM-FE analysis not only provides the ultimate resistance and failure mode of the frame, but also accurately predicts the load-redistribution process inside the connections and the resultant effect on the structural framework.

Nonlinear free vibration of multifunctional sandwich plates with auxetic core and magneto-electro-elastic facesheets of different micro-topological textures: FE approach

This work aims to assess the nonlinear free vibration characteristics of multifunctional sandwich composite plates with auxetic core and magneto-electro-elastic (MEE) facesheets. The novelty of this work is that the combined effects of the electromagnetic (EM) circuits, micro-topological arrangements of MEE material on the coupled frequency response of multifunctional sandwich composite plates with auxetic cores has been investigated for the first time. To this end a higher order finite element (FE) formulation has been developed. The global equations of motion are arrived through Hamilton’s principle and Reddy’s higher order shear deformation theory (HSDT). The C1 continuity requirement of HSDT is fulfilled by considering second order derivative terms as higher order rotational degrees of freedom. Hence, the computational efficiency of this unique FE formulation is found to be better than the commercial numerical software in terms of computational time and costs. Also, the multi-physics field interactions are accurately established. In addition, emphasis has been placed on the geometrical skewness as well which is cumbersome to evaluate through the analytical modeling. Special attention is paid on assessing the influence of coupling fields and EM circuits associated with the auxetic inclination angle, skew angle, micro-topological arrangement of MEE facesheets, core-to-facesheet thickness ratio, length-to-thickness ratio and mechanical boundary conditions on the natural frequency of multifunctional sandwich composite plates, which is first of its kind.

Field calculation of electric dipole excitation of a metafilm printed on a finite‐thickness dielectric slab using the susceptibility homogenization method

Here, the authors calculate the fields due to the electric dipole that excites a homogenized metasurface which is printed on a finite thickness dielectric slab. The problem is solved by replacing the total parts below the periodic array which contain the dielectric slab and the half-space under it, with an effective homogenous half-space. Furthermore, the static interaction constants between dipoles which are located at two different materials’ interface are calculated. Then, with the help of the Lorentz method, the analytical formulae are presented to calculate the surface susceptibility densities of the homogenized metasurface located at two materials’ interface. These analytical formulae can be applied to arrays with both square and rectangular periodicity. An array of circular patches printed on dielectric slabs with different thicknesses is considered to verify the results. The results show good agreement compared to the fields calculated by commercial numerical software FEKO.

A New Semi-Analytical Method for Elasto-Plastic Analysis of a Deep Circular Tunnel Reinforced by Fully Grouted Passive Bolts

The use of fully grouted passive bolts as a reinforcement technique has been widely applied to improve the stability of tunnels. To analyze the behaviors of passive bolts and rock mass in a deep circular tunnel, a new semi-analytical solution is presented in this work based on the finite difference method. The rock mass was assumed to experience elastic–brittle–plastic behavior, and the linear Mohr–Coulomb criterion and the nonlinear generalized Hoek–Brown criterion were employed to govern the yielding of the rock mass. The interaction and decoupling between the rock mass and bolts were considered by using the spring–slider model. To simplify the analysis process, a bolted tunnel was divided into a bolted region and an unbolted region, while the contact stress at the bolted–unbolted interface and the rigid displacement of the bolts were obtained using two boundary conditions in combination with the bisection method. Comparisons show that the results obtained using the proposed solution agree well with those from the commercial numerical software and the in situ test. Finally, parametric analyses were performed to examine the effects of various reinforcement parameters on the tunnel’s stability. The proposed solution provided a fast but accurate estimation of the behavior of a reinforced deep circular tunnel for preliminary design purposes.

The degradable performance of bile-duct stent based on a continuum damage model: A finite element analysis.

Biomedical magnesium alloy stents have become a hot bed of research focus in interventional therapy for nonvascular diseases. In this study, a numerical model for a balloon-expandable bile duct stent made of magnesium alloy with laser sculpture is developed to predict the effects of the degradation of the stent on the biomechanical behavior in the stent-bile duct coupling system. Based on a continuum damage model, the degradable model of the stent is built to understand its performance in an idealized bile duct as it is subject to corrosion over time. The degradation model developed in this study addresses the uniform corrosion and pitting corrosion. By means of the secondary development function of commercial numerical software ANSYS, the finite element analysis procedures were written to control the degradation process based on the technology of element "birth and death," and it is shown how the three-dimensional model and approach give the possibility of analyzing for the degradation mechanism of a magnesium alloy stent in the bile duct or other nonvascular cavities.

Performance, combustion and emission analysis of microalgae Spirulina in a common rail direct injection diesel engine

In the present work, a numerical investigation has been performed on the engine characteristics of a compression ignition (C.I.) engine using D100 (diesel) and AB100 (Algae-biodiesel) as fuels at various compression ratios (16.5–18.5). A commercial numerical software Diesel-RK was used for the simulation work of a direct injection diesel engine. The fluid flow inside the combustion chamber of engine plays a significant role in conducting the performance of an internal combustion engine. Experiments were conducted on the test engine with the optimum compression ratio of 17.5 at full load conditions and the results were compared with the numerical model. The numerical results were found to have respectable treaty against the experimental results. The simulation was carried out for predicting the parameters such as cylinder pressure, exhaust gas temperature, brake thermal efficiency, specific fuel consumption along with the emissions of carbon dioxide, nitrogen oxide, particulate matter at a constant engine speed under 100% load condition. The results indicated that the use of AB100 reduced brake thermal efficiency by 2.73%, torque by 6.66%, exhaust gas temperature by 1.6%, carbon dioxide by 6.1%, nitrogen oxide by 0.5% and particulate matter by 60%. However, the specific fuel consumption at CR 17.5 was increased by 6.4% as compared to diesel.

Parametric Study of an Alpine Wet Debris Flow Event (Novalesa, Torino, Italy) Applying The Finite Volume Method (FVM). Comparison with Available Experimental Data

The Marderello torrent, located at an altitude ranging from 3538m to 900 m above sea level (Novalesa, Cenischia Valley, in Province of Turin) is known for its peculiar capability to generate, with relative frequency, important mud flows and debris (muddy debris flow). Accordingly, the CNR-IRPI (National Research Council) of Turin, since more than twenty years ago, selected this site in order to carry out field observations and measurements campaign. In this paper the muddy-debris flow event, occurred and monitored on July 22, 2016, was considered. The simulation of debris flow phenomena was performed by a 2D Finite Volume Method, solving PDE (Partial Differential Equation) based on the shallow-water approach, through a commercial numerical software. The mathematical-numerical model, beside hydrodynamic model, may also include solid transport and movable river bottom, not explored yet at this stage of the research. First of all, a morphological vectorial model of the basin under study was created and implemented as inputs. The inflow boundary conditions, deriving from the hydrogram consisting of values measured at the monitoring gauge were considered. Several parametric analyses were performed in order to individuate the best values fitting the experimental data concerning the estimated height of the front over time. To this purpose, different available rheological options such as Turbulent-Coulomb, Turbulent-Yield, Turbulent-Coloumb-Yield, and Full Bingham were selected and tested. The comparison with the values collected by the monitored event allowed to define the best values of the parameters to be used. The selected approach and the related model construction can be considered useful and suitable tools in order to study and to simulate this kind of phenomena.

Three dimensional numerical study of different parameters effect on the external magnetic field applied to center the arc of the horizontal mercury discharge lamp

The aim of this paper is to evaluate the magnitude of the external magnetic field to be applied to a horizontal mercury discharge lamp such that the Lorentz forces counterbalance buoyancy forces and the hot region of the arc remains centered inside the lamp with the variation of six parameters of the lamp such as the external temperature of the lamp, envelope thickness, convective loss, Interelectrodeslength, pressure and current supply pointing to the influence of the parameters to the compensating magnetic field value. To achieve this objective, a commercial numerical software “Comsol Multiphysics” is used to implement the model that solves the equations of mass, energy and momentum for laminar compressible flow combined with the Laplace equation for the plasma in a three dimensional.

A New Analytical Model for the Underground Temperature Profile under the Intermittent Operation for Ground-coupled Heat Pump Systems

Abstract Ground-Coupled Heat Pump (GCHP) systems used in commercial buildings are conventionally controlled by some time schedule strategies. So, a reliable method of modeling underground temperature profiles is of great importance for the operation of GCHP systems. Underground temperature profiles are usually predicted by commercial numerical software. This approach is time consuming and lack the flexibility of modeling various cases of GCHP systems. In this paper, a new analytical model based on a composite-medium line-source model is proposed. The new analytical model agrees well with in situ experimental data. An exhaustive simulation is conducted to explore influencing factors on the ground temperature profile, such as operating time, on-off ratio, heat fluxes and thermal conductivity of back-filled grout. These results indicate that a proper operating schedule and heat fluxes are helpful for maintaining the balance of ground temperature, which may offer an opportunity to develop a control strategy based on the heat flux prediction with the help of GCHP system intermittent operation.

Embryo formation from low sperm concentration by using dielectrophoretic force.

A biochip system imitates the oviduct of mammals with a microfluidic channel to achieve fertilization in vitro of imprinting-control-region (ICR) mice. We apply a method to manipulate and to position the oocyte and the sperm of ICR mice at the same time in our microfluidic channel with a positive dielectrophoretic (DEP) force. The positive dielectrophoretic response of the oocyte and sperm was exhibited under applied bias conditions AC 10 Vpp waveform, 1 MHz, 10 min. With this method, the concentration of sperm in the vicinity of the oocyte was increased and enhanced the probability of natural fertilization. We used commercial numerical software (CFDRC-ACE+) to simulate the square of the electric field and analyzed the location at which the oocyte and sperm are trapped. The microfluidic devices were designed and fabricated with poly(dimethylsiloxane). The results of our experiments indicate that a positive DEP served to drive the position of the oocyte and the sperm to natural fertilization (average rate of fertilization 51.58%) in our microchannel structures at insemination concentration 1.5 × 10(6) sperm ml(-1). Embryos were cultured to two cells after 24 h and four cells after 48 h.

Closed form solutions of the heat diffusion equation with a Gaussian source

In the context of the Large Hadron Collider, high energy particles are dumped onto blocks of material that are commonly called beam-dumps. The high energy deposition is almost instantaneous and can be represented by a very high power source for a short period of time. Temperatures can rise above failure limits at the locations of highest energy deposition. Particle beam accelerators are also widely used for medical applications where electron, proton or ion particle beams at energies of the order of megaelectronvolts are used to destroy cancer cells [1]. The motivation of this article is to be able to calculate the temperature fields without turning to numerical simulations that can be very time consuming. We present closed form solutions of the transient heat diffusion problem during the energy deposition. The transient heat diffusion equation assumes infinitely fast propagation of the information throughout the medium, but the diffusion process remains at finite speeds. Energy is deposited in such a small time interval so that the heat flux across the boundaries is assumed to be zero. It follows that the heat diffusion equation can be solved in an infinite medium, by the use of Green’s functions, to provide closed form solutions for the transient temperature field within the pulse time. The range of applicability of these solutions is supported by a parametric relative error analysis. They demand very little computational power and time compared to commercial numerical software.

High-performance bidiagonal reduction using tile algorithms on homogeneous multicore architectures

This article presents a new high-performance bidiagonal reduction (BRD) for homogeneous multicore architectures. This article is an extension of the high-performance tridiagonal reduction implemented by the same authors [Luszczek et al., IPDPS 2011] to the BRD case. The BRD is the first step toward computing the singular value decomposition of a matrix, which is one of the most important algorithms in numerical linear algebra due to its broad impact in computational science. The high performance of the BRD described in this article comes from the combination of four important features: (1) tile algorithms with tile data layout, which provide an efficient data representation in main memory; (2) a two-stage reduction approach that allows to cast most of the computation during the first stage (reduction to band form) into calls to Level 3 BLAS and reduces the memory traffic during the second stage (reduction from band to bidiagonal form) by using high-performance kernels optimized for cache reuse; (3) a data dependence translation layer that maps the general algorithm with column-major data layout into the tile data layout; and (4) a dynamic runtime system that efficiently schedules the newly implemented kernels across the processing units and ensures that the data dependencies are not violated. A detailed analysis is provided to understand the critical impact of the tile size on the total execution time, which also corresponds to the matrix bandwidth size after the reduction of the first stage. The performance results show a significant improvement over currently established alternatives. The new high-performance BRD achieves up to a 30-fold speedup on a 16-core Intel Xeon machine with a 12000× 12000 matrix size against the state-of-the-art open source and commercial numerical software packages, namely LAPACK, compiled with optimized and multithreaded BLAS from MKL as well as Intel MKL version 10.2.

Modelling of a borehole heat exchanger using a finite element with multiple degrees of freedom

An increasing number of installations with underground heat storage have determined the development of new, more accurate and quicker calculation techniques. Therefore, this article shows a numerical model for a single vertical borehole heat exchanger working with underground heat storage. Emphasis has been put on developing a finite element which describes the process of heat exchange. A one-dimensional element with multiple degrees of freedom was used in this work. The changes of grout temperature affect the temperature of the circulating fluid, thus it is necessary to apply a suitable model. The grout area has been divided into three zones, and each one corresponds to a different temperature. Such an attempt allows to determine a more accurate temperature of the fluid. The results obtained for temperature distribution were compared to a model created with the use of Ansys commercial numerical software.