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Aiming to address the challenge of inaccurately describing the curve boundary of the complex design domain in traditional finite element mesh, this paper proposes an improved polygon mesh generation and polygon scaled boundary finite element method (PSBFEM) using non-uniform rational B-spline (NURBS) boundary. In the improved mesh generation scheme, the domain boundary will be accurately described using NURBS curves. Within this framework, a NURBS updating strategy is proposed, allowing the NURBS curve information on the boundary to be updated as the mesh changes. By employing point inversion and knot insertion, additional control points are introduced to ensure that some coincide with the nodes of the elements, thereby guaranteeing the accuracy of subsequent analyses. The boundary elements can be discretized into NURBS elements and conventional elements using SBFEM, whose physical fields are respectively constructed using NURBS basis functions and Lagrange shape functions in the circumferential direction. In the radial direction, by transforming a system of partial differential equations into a system of ordinary differential equations, which can be analytically solved without fundamental solutions. Furthermore, the internal elements can be solved directly with the traditional polygon SBFEM. The numerical examples demonstrate that the proposed method can achieve a high-quality polygon mesh with NURBS updating. Moreover, it effectively solves the corresponding polygon elements and significantly improves the accuracy of the displacement and stress solutions compared to the traditional polygon SBFEM. [ABSTRACT FROM AUTHOR]

The primary objective of this work is to determine the effective permeability of porous media consisting of an isotropic permeable solid matrix containing pores of arbitrary shapes. Fluid flow through the matrix phase is modeled by Darcy's law, while the flow inside the pores follows the Stokes equations. The interfaces between the matrix phase and inclusions are defined by the general form of the Beavers-Joseph-Saffman conditions. To achieve this objective, the Boundary Element Method (BEM) is first developed to solve the coupled Darcy and Stokes problem related to fluid flow through an infinite solid phase containing an arbitrarily shaped pore under a uniform prescribed pressure gradient at infinity. In contrast to the classical BEM where integration equations are often singular, our method, incorporating both finite difference and analytical integration schemes, overcomes this inconvenience. Additionally, compared to the commonly used numerical method based on the finite element method, our approach, which only requires discretization of the solid/fluid interface, significantly enhances computational speed and efficiency. Subsequently, each pore is substituted with an equivalent permeable inclusion, and its permeability is determined. Finally, employing classical micromechanical schemes, the macroscopic permeabilities of the porous material under consideration are estimated. These macroscopic permeability estimates are then compared with the relevant data available in the literature, as well as several numerical results provided by the finite element method. [ABSTRACT FROM AUTHOR]

Purpose: A binary-tree subdivision method (BTSM) for numerical evaluation of weakly singular integrals with discontinuous kernel in the three-dimensional (3D) boundary element method (BEM) is presented in this paper. Design/methodology/approach: In this method, the singular boundary element is split into two sub-elements and subdivided recursively until the termination criterion is met and the subdivision is stopped. Then, the source point is surrounded by one or more spherical cavities determined by the discontinuous kernel function. The sub-elements located in spherical cavities will be eliminated, and the regular triangular or rectangle elements are employed to fill the spherical cavities. Findings: With the proposed method, the obtained sub-elements are automatically refined as they approach the source point, and they are "good" in shape and size for standard Gaussian quadrature. Thus, the proposed method can be used to evaluate singular integrals owing discontinuous kernel function accurately for cases of different element shapes and various source point locations. Originality/value: Numerical examples show that the BTSM is suitable for planar and curved elements of arbitrary regular or irregular shape at various source point locations, and the results have much better accuracy and robustness than conventional subdivision method (CSM) when the kernel function is discontinuous. [ABSTRACT FROM AUTHOR]

In this paper, a modified scaled boundary finite element method (SBFEM) is developed to study static and vibration behaviors of laminated conical shells under the conical coordinate system. In the modified SBFEM, the geometry of the conical shell is defined entirely by scaling the internal surface of the structure. This approach eliminates geometric errors caused by discretization, thereby enhancing modeling accuracy. The three-dimensional problem is simplified to a two-dimensional analysis since discretization is only applied to the boundary of the computational domain. Additionally, the semi-analytic property of the SBFEM allows for the derivation of a linear analytical solution for the laminated conical shell in the radial direction. First, a scaled boundary coordinate system for the scaling surface is established, and a second-order scaled boundary finite element governing equation with variable coefficients is derived for a single layer of the conical shell using the principle of virtual work. Next, the governing equation is transformed into a first-order system by introducing a combined vector of displacement and nodal force, and the stiffness matrices for each layer of the laminated conical shell are obtained using the precise integration method. Finally, an overall analysis of the laminated structure is conducted by assembling each single-layer structure while considering the continuity boundary condition at interfaces. Static and vibration analyses of laminated conical shells are conducted, and the results are compared with those from the literature to demonstrate the adaptability and convergence of the proposed method. Several numerical examples are presented to examine the effects of various geometric parameters, such as thickness, length, semi-vertex angles, layup directions, and stacking sequences, on the responses of the structure. [ABSTRACT FROM AUTHOR]

In this study, we propose two different approaches of a two-step method for solving a system combining the heat and the wave equations. Our focus centers on the transmission problem in two dimensions, with a primary objective of numerically characterizing the distribution of temperature and pressure. First we apply a semi-discretization with respect to time by using the Laguerre transformation. This leads to a sequence of elliptic problems that are fully discretized either by the boundary integral equation method or by the fundamental sequences method. The presented numerical examples justify the applicability and efficiency of both schemes. • A coupled parabolic-hyperbolic transmission problem in the two-dimension domain is considered. • The problem is reduced to a sequence of elliptic problems using the Laguerre transformation in time. • The obtained sequence is fully discretized by two methods (BIEM and FSM). • Results of numerical examples are given for both proposed schemes. [ABSTRACT FROM AUTHOR]

Spacecraft parts accumulate damage during operation and defects that are invariably present even in new designs may grow. This leads to changes in the behavior of individual parts of the space vehicle and, consequently, to the risk of fracture. A more accurate assessment of spacecraft safety requires internal defects to be included in the material models under consideration. One of the main hazardous effects on space objects is multiple temperature heating and cooling due to periodic action of solar rays. This paper presents a study of thermal conduction of media containing cracks. It is carried out with the help of a technique developed by the authors to determine the effective thermal conductivity of materials and based on approximate numerical solution of the steady-state thermal conduction problem for a three-dimensional medium with cracks by the boundary element method. This technique allows to obtain the distribution of the temperature field and heat flux density at any point of the body under consideration, as well as to calculate the effective parameters of materials with high accuracy at relatively low calculation time using ordinary personal computers of average power. The basis of the numerical method presented in this paper is the decomposition of the desired solution into a series of some pre-calculated analytical solutions of the heat conduction equations. The dependence of the effective thermal conductivity on the density of thermally insulated cracks was considered. The formula of this dependence is proposed. Verification of the proposed methodology was carried out by comparing the numerical results of a number of problems with the results of other authors. • The technique for numerical modeling of the thermal conduction of 3D media containing cracks is presented. • The numerical results were compared with the well-known analytical solutions and showed good agreement. • The dependence of the effective thermal conductivity on the density of thermally insulated cracks was considered. [ABSTRACT FROM AUTHOR]

One of the important tasks of space flight safety is the ability of a wing to maintain stability in an oncoming turbulent flow. In this case, the spacecraft must move the greatest distance. The paper studies the motion of a thin plate near a boundary in an oncoming flow of rarefied gas. At low Reynolds numbers, the effect of the boundary on the plate is studied, and the possibility of self-propulsion is shown. • The drag force of the plate increases sharply as the distance to the boundary decreases. • The lifting force and moment change from the center of the plate to the boundary decreases. • The point of application of the resultant force shifts to the rear edge of the plate. • Self-motion is possible for plates that have a common rib. [ABSTRACT FROM AUTHOR]

Seakeeping of a ship under waves is vital for safety, with strong resonance occurring when two conditions are met: (1) large wave loads, and (2) wave frequency being close to the natural frequency. Prior research focused on resonant phenomena, nonlinear traits, and failure modes, but the dominant condition for resonance in ocean-going ships is unclear. This study developed a mathematical model using the boundary element method (BEM) for an advancing ship under small-amplitude waves. An open-source solution was proposed, utilizing NEMOH for hydrodynamic coefficients and a Python code for dynamic equation solving. Validated with KRISO Container Ship (KCS) data, the mathematical model accurately predicts ship motions. Findings show that ship heave resonance is influenced by both conditions, but the second condition affects rolling more, and the first condition controls pitch more. This is more evident in high-speed ships and is less affected by ship size variations. [ABSTRACT FROM AUTHOR]

This paper presents a hydroelastic analysis of a pontoon-type Very Large Floating Structure (VLFS) with multiple barriers of varying porosities. The Mindlin plate theory is applied to model the VLFS, while the linear potential wave theory is used to model fluid motions. For interactions between the fluid and impermeable solid surfaces, a boundary condition equating normal fluid and structural velocities is imposed. For fluid interactions with perforated barriers, an empirical model is adopted, where the pressure of fluid passing through the barriers is assumed to drop in a quadratic relationship with the fluid velocity. The mathematical model is solved using an iterative numerical framework based on the finite element method and dual boundary element method. Numerical examples of VLFSs with single and multiple barriers of different porosities are presented. The numerical results indicate that the number and porosity of barrier attachments can be optimized to minimize the hydroelastic responses of the VLFS under specific wave conditions. A combination of a perforated barrier placed in front of an impermeable barrier demonstrates good performance in mitigating the VLFS’s hydroelastic responses, with reasonable horizontal forces on the mooring system as compared to other possible combinations of barrier porosities. [ABSTRACT FROM AUTHOR]

With the expansion of seabed gas hydrate exploitation, particle-reinforced cement is widely used in well cementing. However, the estimation of heat transfer and thermal conductivity for hollow cylinder composites reinforced with particles remains ambiguous and requires further clarification. This paper employs the inclusion-based boundary element method (iBEM) to calculate both the local field distribution and effective thermal properties of particle-reinforced hollow cylinder composites (PRHCC). Particle interactions are simulated through the introduction of the eigen-temperature gradient, and the boundary effect is modeled using the boundary element method. Numerical simulations explore the influence of interparticle interactions, particle volume fraction, particle properties, and particle distribution on the thermal properties of PRHCC. The results show that the particle interactions have distinct effects in different directions, significantly altering the temperature spread in the central and lower regions within the particles, and then affecting the overall thermal properties of PRHCC. This method serves as a valuable reference for the engineering industry, providing insightful guidance for optimizing design, fabrication processes, and material selection, particularly in components with thermal considerations. [ABSTRACT FROM AUTHOR]

The unpreconditioned H‐TFETI‐DP (hybrid total finite element tearing and interconnecting dual‐primal) domain decomposition method introduced by Klawonn and Rheinbach turned out to be an effective solver for variational inequalities discretized by huge structured grids. The basic idea is to decompose the domain into non‐overlapping subdomains, interconnect some adjacent subdomains into clusters on a primal level, and enforce the continuity of the solution across both the subdomain and cluster interfaces by Lagrange multipliers. After eliminating the primal variables, we get a reasonably conditioned quadratic programming (QP) problem with bound and equality constraints. Here, we first reduce the continuous problem to the subdomains' boundaries, then discretize it using the boundary element method, and finally interconnect the subdomains by the averages of adjacent edges. The resulting QP problem in multipliers with a small coarse grid is solved by specialized QP algorithms with optimal complexity. The method can be considered as a three‐level multigrid with the coarse grids split between primal and dual variables. Numerical experiments illustrate the efficiency of the presented H‐TBETI‐DP (hybrid total boundary element tearing and interconnecting dual‐primal) method and nice spectral properties of the discretized Steklov–Poincaré operators as compared with their finite element counterparts. [ABSTRACT FROM AUTHOR]

The article "Wave scattering by plate array metacylinders of arbitrary cross-section" delves into the interaction of water waves with plate array metastructures, focusing on various shapes like circular metacylinders and graded metawedges. The study uses a transform-based method to analyze wave scattering without homogenization, revealing insights into wave frequencies above resonance. The findings suggest potential applications in coastal protection and wave energy conversion, particularly with graded plate array metastructures. Other studies by researchers like Porter and Evans contribute to understanding wave behavior and its applications in different fields, such as wave energy converters and electromagnetic metagratings. [Extracted from the article]

The article "Hydrodynamic performance of a floating fluid-filled membrane breakwater: experimental and numerical study" delves into the analysis of a Floating Flexible Membrane Breakwater (FFMB) through physical model experiments and numerical methods. The research establishes a motion equation for the FFMB, examines the impact of structural parameters on wave transmission and reflection coefficients, and proposes optimal parameters for practical engineering applications. By emphasizing accurate modeling and analysis, the study aims to provide a theoretical foundation for understanding the interaction between membrane structures and waves, showcasing the FFMB's ability to effectively attenuate waves within specific frequency ranges. [Extracted from the article]

A plasmonic nanosensor is proposed and investigated its sensitivity using the optical properties of plasmonic nanoparticles. To this end, we first consider the nanosensor consisting of bowtie nanoparticles. Then, the nanosensor performance is examined under different factors such as the refractive index of the background environment, the height, and length of the nanoparticles. The proposed bowtie nanoparticles, in this work, are made of gold. The boundary element method is used to simulate the nanosensor. The extinction cross-section is computed in terms of wavelength and the effect of various factors on the resonance wavelength of localized surface plasmon is investigated. It is shown that the nanosensor investigated in this research has a high sensitivity to the changes in the refractive index of the studied sample. The sensitivity of the nanosensor is obtained as 650 nm/RIIU. In addition, the required spectral range can be arbitrarily adjusted by the type of nanoparticles. [ABSTRACT FROM AUTHOR]

This study presents a novel method for wideband acoustic analysis using the Boundary Element Method (BEM), addressing significant computational challenges. Traditional BEM requires repetitive computations across different frequencies due to the frequency-dependent system matrix, resulting in high computational costs. To overcome this, the Hankel function is expanded into a Taylor series, enabling the separation of frequency-dependent and frequency-independent components in the boundary integral equations. This results in a frequency-independent system matrix, improving computational efficiency. Additionally, the method addresses the issue of full-rank, asymmetric coefficient matrices in BEM, which complicate the solution of system equations over wide frequency ranges, particularly for large-scale problems. A Reduced-Order Model (ROM) is developed using the Second-Order Arnoldi (SOAR) method, which retains the key characteristics of the original Full-Order Model (FOM). The singularity elimination technique is employed to directly compute the strong singular and super-singular integrals in the acoustic equations. Numerical examples demonstrate the accuracy and efficiency of the proposed approach, showing its potential for large-scale applications in noise control and acoustic design, where fast and precise analysis is crucial. [ABSTRACT FROM AUTHOR]

The paper deals with an application of the artificial immune system (AIS) and the particle swarm optimizer (PSO) to the optimization of composites with thin rigid fibers. The boundary value problem is solved using the boundary element method (BEM). The numerical examples demonstrate the optimization of the distribution and orientation of fibers in a composite. The objective functions depend on effective elastic properties. Two separate independent optimization methods are used to confirm the correctness of the obtained results (AIS and PSO). The bioinspired approach shows that the method based on the artificial immune system or particle swarm optimizer is an efficient technique for solving computer-aided optimal design problems (maximalization of the Young's modulus or Poisson's ratio) and allows for the development of new materials. [ABSTRACT FROM AUTHOR]

Purpose: The study aims to investigate the effectiveness of DYAD606, a viscoelastic material known for its high frequency and temperature dependency, in enhancing the damping capacity of structures subjected to vibro-acoustic issues. The research question revolves around understanding how DYAD606 affects the vibration and acoustic behavior of sandwich plates, particularly focusing on its damping properties concerning frequency and temperature variations. Methods: Employing a numerical approach, the study utilizes Finite Element Method (FEM), Boundary Element Method (BEM), and Numerical Asymptotic Method (NAM) to analyze the vibration and acoustic characteristics of sandwich plates with DYAD606 cores. The formulation of the equation of motion based on Hamilton's principle and the construction of a structural modal basis facilitate comprehensive analysis. Results: The research reveals that DYAD606 effectively enhances damping across various temperature conditions. Despite a decrease in structural rigidity with rising temperatures, there is a notable improvement in acoustic damping, as evidenced by parameters such as sound transmission loss factor (STL) and sound pressure factor. Conclusion: Viscoelastic materials like DYAD606 demonstrate efficacy in attenuating vibrations and reducing noise levels in structural applications. The study underscores the importance of considering both frequency and temperature dependencies when evaluating the damping capabilities of such materials, providing insights for the development of effective damping techniques in modern systems and installations. [ABSTRACT FROM AUTHOR]

Purpose: In this paper, the vibro-acoustic characteristics of laminated composite multi-stepped cylindrical shells immersed in fluid medium are investigated. Method: The first order shear deformation theory (FSDT) and the variational principles are applied to formulate the vibration model and the Kirchhoff–Helmholtz integral equation is employed to analyze the acoustic characteristics of the laminated composite multi-stepped cylindrical shells. The displacement field of the structure are expanded by Jacobi polynomials for vibration analysis and the Chebyshev polynomials for acoustic analysis are used. A set of Chebyshev collocation points are used to formulate the algebraic system of the acoustic integral equations, and the CHIEF method is used to solve the non-uniqueness problem. Results: Numerical results are given for vibration analyses and acoustic characteristics analyses of the laminated composite multi-stepped cylindrical shells. The accuracy and reliability of the present method is verified by comparing with results obtained by references and the coupled finite element method/boundary element method (FEM/BEM). Then, the influence of the geometric, material properties, boundary condition, fluid medium and force types on vibro-acoustic behaviors of the laminated composite multi-stepped cylindrical shells is provided through several numerical examples. [ABSTRACT FROM AUTHOR]

Due to the wide application of closely spaced multi-well horizontal pads for developing unconventional gas reservoirs, interference between wells becomes a significant concern. Communication between wells mainly occurs through natural fractures. However, previous studies have found that interwell communication through natural fractures is varied, and non-communication also appears in the mid and late stages of production due to natural fracture closure. This study proposes a boundary element method for coupling multi-connected regions for the first time. Using this method, we coupled multiple flow fields to establish dual-well models with various connectivity conditions of the stimulated reservoir volume (SRV) region. These models also take into consideration of adsorption and desorption mechanism of natural gas as well as the impact of fracturing fluid retention. The study found that when considering the non-communication of SRV regions between multi-well horizontal pads, the transient behavior of the targeted well exhibits a transitional flow stage occurring before the well interference flow stage. In addition, sensitivity analysis shows that the well spacing and production regime, as well as the connectivity conditions of the SRV region, affect the timing of interwell interference. Meanwhile, the productivity of the two wells, reservoir properties, and fracturing operations affect the intensity of interwell interference. [ABSTRACT FROM AUTHOR]

It is known that numerical simulations of moving contact lines are challenging owing to the fact that multiple scales are inherently involved. In this paper, we propose an efficient boundary element method for numerical simulations of dynamic wetting/dewetting. The flow domain is truncated in a mesoscopic scale, where boundary conditions resulted from a wedge flow and the asymptotic theory of the intermediate region are imposed. This procedure avoids the high resolution near the contact line in full-scale simulations and hence significantly reduces the computational cost. Numerical tests for dip coating problem show that the meniscus profiles and slopes produced by the proposed method agree well with high-resolution full-scale simulations as well as the local asymptotic theory. [ABSTRACT FROM AUTHOR]

The novelty of this work is the development of a new fractional boundary element model based on the Caputo derivative to investigate anomalous thermal stress effects on cement-based materials. To obtain the BEM integral equations for the proposed formulation, we employ the weighted residuals technique, with the anisotropic fundamental solution serving as the weighting function in the anomalous heat governing equation. The Caputo fractional derivative was employed as an integrand for the domain integral of the proposed formulation. The time step selection is less dependent on the time derivative order. This allows the approach to overcome the non-locality of the fractional operators. The key benefit provided by the suggested formulation is the ability to analyze situations with tiny values of the fractional time derivative. The current BEM methodology proves that it is a useful tool for solving fractional calculus problems. [ABSTRACT FROM AUTHOR]

This paper presents the thermo-acoustic frequency response of an un-baffled rectangular panel subjected to an external excitation load. A boundary element method BEM has been employed taking into account the Kirchhoff-Helmholtz K-H integral equation for the acoustic pressure and with the fluid-plate interface boundary condition the acoustic pressure jump over the panel is calculated. The thermal effects are considered regarding in the form of a uniform increment of temperature of the panel and are analysed in order to prevent the buckling phenomena. The excitation force considered is in the form of a concentrated load at some point of the panel and the deformation modes correspond to the vacuum case. Applying a collocation method for the panel equation, a frequency transfer function is obtained that relates the deflexion of the panel with the applied load. The effect of several geometric parameters, different thermal loads and location of the load applied on the acoustic radiated power and the acoustic efficiency spectrum are evaluated. Furthermore, the influence of the excitation frequency on the sound directivity is evaluated. The verification of the method is proven with other works. [ABSTRACT FROM AUTHOR]

The acoustic wave equation is solved in time domain with a boundary element formulation. The time discretisation is performed with the generalised convolution quadrature method and for the spatial approximation standard lowest order elements are used. Collocation and Galerkin methods are applied. In the interest of increasing the efficiency of the boundary element method, a low-rank approximation such as the adaptive cross approximation (ACA) is carried out. We discuss a generalisation of the ACA to approximate a three-dimensional array of data, i.e., usual boundary element matrices at several complex frequencies. This method is used within the generalised convolution quadrature (gCQ) method to obtain a real time domain formulation. The behaviour of the proposed method is studied with three examples, a unit cube, a unit cube with a reentrant corner, and a unit ball. The properties of the method are preserved in the data sparse representation and a significant reduction in storage is obtained. [ABSTRACT FROM AUTHOR]

A numerical study was carried out to analyze the phenomenon of natural convection in a porous medium saturated with nanofluid. In the study, the boundary element method was used for computational modeling. The fluid flow through a porous matrix is described using the Darcy–Brinkman–Forchheimer momentum equation. In addition, a mathematical model for nanofluids was used, which follows a single-phase approach and assumes that the nanoparticles within a fluid can be treated as an independent fluid with effective properties. A combination of single- and sub-domain boundary element methods was used to solve the relevant set of partial differential equations. The method was originally developed for pure flow scenarios, but also proves to be effective in the context of fluid flow through porous media. The results are calculated for the case of two- and three-dimensional square cavities. In addition to various values of dimensionless control parameters, including the porous Rayleigh number (Rap), Darcy number (Da), porosity (ϕ) and nanoparticle volume fractions (φ), the effects of the inclination angle of the cavity on the overall heat transfer (expressed by the Nusselt number (Nu)) and fluid flow characteristics were investigated. The results indicate a pronounced dependence of the overall heat transfer on the introduction of nanoparticles and inclination angle. The heat transfer in a two-dimensional cavity is increased for higher values of Darcy number in the conduction flow regime, while it is suppressed for lower values of Darcy number in the Darcy flow regime. In the case of a three-dimensional cavity, increasing the volume fraction of nanoparticles leads to a decrease in heat transfer, and furthermore, increasing the inclination angle of the cavity considerably weakens the buoyancy flow. [ABSTRACT FROM AUTHOR]

Fracture geometries and drainage radius are essential parameters for developing a reasonable development plan for a single fractured well. However, owing to fracture hits, the complex fracture geometries bring challenges for parameter estimations. This paper establishes a well testing based model for a finite-conductivity fractured vertical well in radial composite reservoirs with dynamic supply and fracture networks. Based on the successive steady-state method, the point source function, pressure superposition principle, and boundary element method are used to solve the reservoir model, and the methods of discrete fracture and pressure superposition are used to solve the fracture model. By introducing the rate-normalized pseudopressure and material balance time, the variable fluid flux is equivalent to the constant fluid flux. The drainage radius value and fracture geometries are solved by fitting the log-log curves of pressure response, and case studies are performed. The results show that the drainage radius increases with the increase of production time and finally tends to a specific value, and it has an excellent exponential relationship with time. Also, the fracture geometries of the typical well are multiple-radial fracture networks. Through the study of dynamic drainage radius, the controlled reserves of single wells in unconventional gas reservoirs can be better determined, and it can also provide a theoretical basis for fracture evaluation, productivity prediction, and enhanced recovery study of the same type of tight gas reservoir. [ABSTRACT FROM AUTHOR]

A preconditioner is proposed for Laplace exterior boundary value problems on multi-screens. To achieve this, the quotient-space boundary element method and operator preconditioning are combined. For a fairly general subclass of multi-screens, it is shown that this approach paves the way for block diagonal Calderón preconditioners which achieve a spectral condition number that grows only logarithmically with decreasing mesh size, just as in the case of simple screens. Since the resulting scheme contains many more degrees of freedom than strictly required, strategies are presented to remove almost all redundancy without significant loss of effectiveness of the preconditioner. The performance of this method is verified by providing representative numerical results. Further numerical experiments suggest that these results can be extended to a much wider class of multi-screens that cover essentially all geometries encountered in practice, leading to a significantly reduced simulation cost. [ABSTRACT FROM AUTHOR]

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Copyright of Umm Al-Qura University Journal of Engineering & Architecture (Springer Nature) is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The issue of low-frequency structural noise radiated from high-speed railway (HSR) box-girder bridges (BGBs) is a significant challenge worldwide. Although it is known that vibrations in BGBs caused by moving trains can be reduced by installing multiple tuned mass dampers (MTMDs) on the top plate, there is limited research on the noise reduction achieved by this method. This study aims to investigate the noise reduction mechanism of BGBs installed with MTMDs on the top plate. A sound radiation prediction model for the BGB installed with MTMDs is developed, based on the vehicle–track–bridge coupled dynamics and acoustics boundary element method. After being verified by field tested results, the prediction model is employed to study the reduction of vibration and noise of BGBs caused by the MTMDs. It is found that installing MTMDs on top plate can significantly affect the vibration distribution and sound radiation law of BGBs. However, its impact on the sound radiation caused by vibrations dominated by the global modes of BGBs is minimal. The noise reduction achieved by MTMDs is mainly through changing the acoustic radiation contributions of each plate of the bridge. In the lower frequency range, the noise reduction of BGB caused by MTMDs can be more effective if the installation of MTMDs can modify the vibration frequency and distribution of the BGB to avoid the influence of small vibrations and disperse the sound radiation from each plate. [ABSTRACT FROM AUTHOR]

The steel plate shear walls (SPSWs) have been proven effective in reinforced concrete frames (RCFs) as a lateral force‐resistant structure. Despite of advancements, accurately predicting the ultimate shear capacity of RCFs with SPSWs remains challenging using current simplified models. Additionally, the flexural capacity design procedure for the boundary elements (beams and columns) in previous studies of RCF‐SPSWs involved intricate iterative procedures, hindering its widespread implementation. To address the two issues, this paper investigates the pushover responses and the plate‐frame interaction (PFI) of an RCF‐SPSWs system using theoretical and numerical methods. There are three main contributions. First, a theoretical model of ultimate shear capacity for RCF‐SPSWs is proposed, which can also be used to predict shear contributions of boundary frames in RCF‐SPSWs. Calculation errors for ultimate shear capacity of RCF‐SPSWs and shear contribution from the boundary frame are only 3.7% and 6.7% respectively, which are reduced dramatically compared with the traditional model. A simplified schematic diagram for the global collapse mechanism (uniform distribution of plastic hinges within a structure) of RCF‐SPSWs is developed to facilitate the calculation of internal work and reaction forces. Secondly, a flexural capacity design method for the boundary elements to avoid in‐span plastic hinges is proposed. The proposed method enables the achievement of direct estimation of the flexural demands that could trigger a global collapse mechanism, all without intricate iterative procedures. The applicability of current assumptions for the design of steel boundary frame in RCF‐SPSWs system is discussed, and engineering suggestions are provided to ensure safer and more economic designs. Comparison results confirmed the applicability of the proposed design method, which can be adopted to achieve the global collapse mechanism for RCF‐SPSW system. Thirdly, impacts of yielding panel actions on the flexural capacity of boundary elements of RCF‐SPSWs are clarified. Comparison results demonstrated that adding SPSWs to an RCF alters the axial force on boundary elements and significantly impacts the flexural capacity. A design suggestion is made to emphasize the importance of avoiding the balanced failure of boundary elements. The proposed theoretical model can be used to economize the cross‐section of boundary elements in RCF‐SPSWs system under seismic loads due to accurate prediction of their shear contribution; the proposed flexural capacity design method can achieve a global collapse mechanism, and thus the structural safety and energy dissipation capacity are improved; moreover, the building design efficiency is also improved due to avoidance of intricate iterative procedures. [ABSTRACT FROM AUTHOR]

As one of the main numerical methods, the boundary element method boasts the advantages of fast computation speed and high accuracy. Based on the considerations of the influence of pressure drop, perforation height, skin coefficient, reservoir coefficient, and reservoir radius on the seepage law, a novel three-dimensional seepage model for vertical wells was established using the Laplace transform method and Stehfest numerical inversion method. The model was utilized to examine the velocity of pressure propagation and drop amplitude, revealing that the near-well area experienced faster propagation and drop than the far-well area. During dimensional analysis, it was observed that neglecting the effects of formation pressure change could lead to a substantial increase in the dimensional error of bottom hole pressure, with a maximum error of 9.45% recorded in this study. Additionally, a sensitivity analysis was conducted on perforation length, wellbore reservoir coefficient, skin coefficient, and reservoir radius to further elucidate the seepage law of vertical wells. This study provides theoretical guidance for oil and gas production. The original contribution of this research lies in the incorporation of formation pressure changes into the three-dimensional seepage model of vertical wells for the first time, which significantly enhances the model's accuracy and practicality. [ABSTRACT FROM AUTHOR]

The optical cross sections of plasmonic nanoparticles are intricately linked to their morphologies. Accurately capturing this link could allow determination of particles' shapes from their optical cross sections alone. Electromagnetic simulations bridge morphology and optical properties, provided they are sufficiently accurate. This study examines key factors affecting simulation precision, comparing common methods and detailing the impacts of meshing accuracy, dielectric function selection, and substrate inclusion within the boundary element method. To support the method's complex parameterization, we develop a workflow incorporating reconstruction, meshing, and mesh simplification, to enable the use of electron tomography data. We analyze how choices of reconstruction algorithm and image segmentation affect simulated optical cross sections, relating these to shape errors minimized during data processing. Optimal results are obtained using the total variation minimization (TVM) reconstruction method with Otsu thresholding and light smoothing, ensuring reliable, watertight surface meshes through the marching cubes algorithm, even for complex shapes. [ABSTRACT FROM AUTHOR]

In this present work, the performance of a two‐layered thick porous breakwater of trapezoidal structure is investigated under the action of irregular waves. To investigate the physical problem, the classical linear water wave theory has been taken into consideration. To analyze the effect of irregular waves on the multilayered structure, two unidirectional wave spectra, namely the Pierson–Moskowitz and JONSWAP spectra based on the frequency domains are considered. Three different sea states are taken to analyze the impact of irregular waves on the multilayered porous breakwater. The constant boundary element method is used to handle the aforementioned boundary value problem, which is considered one of the most efficient numerical tools for handling complex structured open sea problems. Several wave characteristics associated with the spectral density functions are demonstrated and analyzed for a variety of structural and spectral parameters. The findings suggest that the adoption of suitable porous material for the construction of these breakwaters can significantly enhance the energy dissipation and thereby minimize the wave force on the structure. [ABSTRACT FROM AUTHOR]

For problems with very fine surface meshes, typically the most time-consuming step of a boundary element method (BEM, also called a panel method) is solving the final linear system of equations. Many have already studied how to efficiently solve the dense, asymmetric systems which arise in elliptic BEMs. However, this has not been studied for a supersonic aerodynamic BEM, for which the governing PDE is hyperbolic. Due to this hyperbolic character, the matrix equation which arises from a supersonic BEM has a large number of identically zero elements. But the resulting linear system of equations is also not sparse in the standard sense. Hence, the efficient solution of the linear system of equations arising in a supersonic BEM is here considered. A novel sorting algorithm is developed whereby the non-zero elements may be arranged into a useful structure with minimal cost. A novel direct solution method is developed here based on fast Givens rotations and the QR decomposition. This novel solver leverages the unique matrix structure to solve the supersonic system of equations more quickly than traditional direct methods. This novel method is then compared to other direct and iterative matrix solvers and is shown to be more robust than iterative solvers and more efficient than other direct solvers, with a computational time complexity of approximately O (N 2.5) . [ABSTRACT FROM AUTHOR]

Extensive three-dimensional boundary-integral simulations are presented for the steady-state, low-Reynolds-number motion of a non-wetting deformable drop in another liquid on an inclined solid wall. The drop remains separated from the wall by a lubricating film. The boundary-integral formulation is based on the half-space Green function. The focus is on the challenging case of small tilt angles $\theta$ combined with high drop-to-medium viscosity ratios $\lambda$ , when the drop travels with strong hydrodynamical interaction very close to the wall. Simulations to steady state have required ultrahigh drop surface resolutions (to $3\times 10^5$ boundary elements) achieved through multipole acceleration and combined with novel regularization to fully eliminate near-singular behaviour of the double-layer integrals due to small clearance. Non-dimensional drop speed $U$ is presented for $\theta \geq 7.5^\circ$ , $\lambda \leq 300$ and in a broad range of Bond numbers $B$ , covering from nearly spherical to strongly pancaked drops. The results are consistent with published experiments on liquid–liquid systems. At small $\theta$ and $\lambda \gg 1$ , $U$ is a strong, decreasing function of $B$ ; the asymptotic regime $U\to 0$ at $B\to 0$ is not observed in the simulated range. For small $B$ , the dimpled thin-film geometry is insensitive to $\lambda =1\unicode{x2013}300$. For pancaked drops, the lubrication film is much thicker for $\lambda =1$ than for $\lambda \gg 1$ drops. Approximate thin-film uniformity in the drop motion direction is confirmed for pancaked, but not for $B\ll 1$ , drops. Kinematics of drop motion shows that neither perfect tank treading, nor perfect rolling can be approached for liquid–liquid systems in the purely hydrodynamical formulation. The methodology is applicable to other problems and can allow for direct inclusion of short-range colloidal forces in three-dimensional boundary-integral simulations. [ABSTRACT FROM AUTHOR]

This paper presents the acoustic analysis of a three-dimensional cylindrical shell model under electromagnetic vibration, a critical factor affecting the performance of electric motors in various applications such as automotive, aerospace, and industrial systems. The study provides a multidisciplinary approach that integrates electromagnetics, structural vibration, and acoustics, solved using the fast multipole boundary element method (FMBEM). The results summarize the validation of the analytical models and numerical simulations, offering insights into effective vibration reduction methods. The conclusions indicate that the 3-D numerical analysis using FMBEM aligns well with the analytical solution for the sound pressure in the exterior acoustic domain of the cylindrical shell model. The paper contributes valuable insights for the design of low-noise motors and the control of electromagnetic vibration and noise in electric motors. [ABSTRACT FROM AUTHOR]

In this paper, vibroacoustic analysis of an L-shaped acoustic cavity comprising of rigid and laminated composite thin and flexible walls with opening has been performed by coupling multi-domain boundary element (BE) method with finite element (FE) method, where the cavity is divided into several domains with intermediate interface layers and the continuity conditions have been established at the interface. Finite element structural analysis of the interacting enclosure has been conducted to extract the mobility relationship between pressure and velocity at the interacting walls and apply that to the pressure-velocity multi-domain BE formulation of the interior acoustic cavity. Absorbent layers have been applied at multiple walls to investigate their effects on sound pressure levels at the boundary and inside the domain. Radiation impedance and admittance relationship have been implemented to model the opening and the absorbent layers at the boundary respectively. An in-house software incorporating the aforementioned features has been developed to solve practical vibroacoustic engineering problems of irregular-shaped cavities. The present program has been verified with analytical and experimental data available in the literature to ensure accuracy. It has been demonstrated that the shape of the acoustic domain along with the presence of opening alters the modal characteristics of the structure causing considerable modifications in the sound pressure level (SPL) pattern. Examples reveal that one can restrict the acoustic output at the resonant frequencies by suitably adding absorbents. [ABSTRACT FROM AUTHOR]

Image restoration is a critical task in computer vision that involves recovering an original image from corrupted or damaged versions of it. Traditional image restoration relies on interpolation and completion techniques, such as Navier–Stokes equations and the fast multipole boundary element method. However, these methods often fail to capture the advanced semantic information of an image, leading to inaccurate restoration results. In recent years, generative adversarial networks (GANs) have emerged as a practical approach in computer vision for image restoration tasks, as they can address image restoration issues related to damaged or missing image information. GANs are a deep‐learning network structure with a generator and discriminator. In image restoration, the generator is employed to restore damaged images, and the discriminator is used to assess the authenticity of the repair results. Competition between the generator and discriminator improves the quality of the repair results. This study proposes a novel generative image restoration method that utilizes contextual and perceptual semantic information mechanisms to strengthen GANs. Our approach demonstrates the effectiveness of GANs in restoring images through learning how to fuse the missing or damaged parts of an image with the undamaged parts surrounding them, resulting in visually appealing restoration results. [ABSTRACT FROM AUTHOR]

This study introduces a new modelling approach that leads to a more efficient process for constructing the matrix system arising from the discretization of integral equations by the boundary element method. This method uses the matrix structure employed in the direct interpolation technique, yielding computational efficiency while maintaining precise outcomes and ensuring convergence as the mesh is refined. To demonstrate the effectiveness of this novel numerical technique, it is applied to solve two-dimensional problems governed by the Laplace equation. [ABSTRACT FROM AUTHOR]

In this work we develop an a posteriori error estimator for mixed finite element methods of Darcy flow problems with Robin-type jump interface conditions. We construct an energy-norm type a posteriori error estimator using the Stenberg post-processing. The reliability of the estimator is proved using an interface-adapted Helmholtz-type decomposition and an interface-adapted Scott–Zhang type interpolation operator. A local efficiency and the reliability of post-processed pressure are also proved. Numerical results illustrating adaptivity algorithms using our estimator are included. [ABSTRACT FROM AUTHOR]

This study investigated the random scattering effect in sedimentary basins with uncertain geotechnical parameters under vertical SV waves using multiplicative dimensional reduction method. The influence of the depth-to-radius ratio of basins and variability of geotechnical parameters on the random scattering effect was explored. The results indicate that the scattering in sedimentary basins significantly amplifies the uncertainty. The variability of displacement amplitude factors of basins is significantly affected by the depth-to-radius ratio of basins, providing a 2- or 3-time difference under high-frequency waves. The coefficient of variations of displacement amplitude factors has a nonlinear amplification relationship with those of geotechnical parameters. [ABSTRACT FROM AUTHOR]

In this paper, a time-domain solution for Rayleigh wave scattering from a complex site of Alpine Valley is presented based on the scaled boundary finite element method (SBFEM). Both the near-field region and the far-field region are assumed to be homogeneous, isotropic linear elastomers, where the near-field region is discretized using the quadtree method and the far-field region is simulated with a displacement unit impulse response function. The input of Rayleigh waves is solved by the equivalent loading method. The scattering behavior of seismic waves in alpine valleys is comprehensively analyzed, and the results are of theoretical significance for site safety evaluation and seismic defenses. [ABSTRACT FROM AUTHOR]

The scaled boundary finite element method (SBFEM) is implemented in ABAQUS through the user subroutine interface. The accuracy of the proposed method and computer program are verified by using two benchmark examples. With the coupled SBFEM and standard finite element method (FEM), the dynamic interaction model of concrete dam – reservoir – foundation considering the geometrical nonlinearity of transverse joints is established using the viscous-spring absorbing boundary conditions. The overlaying element technique is applied to define the contact interface of transverse joints. The dynamic characteristics and linear seismic response of the Koyna gravity dam have been analyzed using polyhedral elements. Finally, nonlinear seismic analysis of the NG5 arch dam has been conducted. The calculated results are in good agreement with those of ABAQUS built-in elements. Moreover, numerical examples demonstrate that proposed method has high computational accuracy and can be applied to the dynamic analysis of complex engineering structures. [ABSTRACT FROM AUTHOR]

This paper delves into a significant area of research, exploring the application of the standard boundary element method (BEM) to analyze inverse acoustic frequency scattering problems in 2D space using a rigid corrugated circular object. The inverse problem is reformulated as an optimization problem, with the boundary of the scatterer parametrized to reduce the number of optimization variables. The influence of these parameters on imaging results based on near-field data is examined. The analysis uses a flat wave illuminating the object along the positive x-axis direction. The study evaluates the accuracy of the solution across various parameters defining the boundary of the analyzed object. The findings, which significantly contribute to advancements in computational methods, non-destructive testing, and the understanding of functional properties of materials and structures, offer valuable insights into numerical techniques and their practical engineering applications. [ABSTRACT FROM AUTHOR]

ABSTRACT The inversion of subsurface geological structures is a crucial approach for gaining insights into the internal composition of the earth. In this paper, we propose a novel inversion method combining the nonsingular indirect boundary element method (IBEM) with the multistrategy particle swarm optimization (MSPSO) algorithm, tailored for accurately inverting 3D subsurface cavities. Leveraging the semi‐analytical nature of IBEM offers advantages such as dimensionality reduction, automatic fulfillment of radiation conditions at infinity, and high computational accuracy. Furthermore, to augment global optimization and local search capabilities, an MSPSO algorithm is introduced. Employing multiple optimization strategies enhances particle diversity, accelerates algorithm convergence, and mitigates the risk of local optima. Through the consideration of subsurface cavities with varying parameters, this method quickly identifies the approximate location of the cavity within a wide search range. The final results demonstrate that the proposed method can simultaneously and accurately invert the 3D spatial position, size, and orientation of the cavity. [ABSTRACT FROM AUTHOR]

This study examines the three-dimensional dynamics of two gas bubbles near a horizontal rigid wall, focusing on how inter-bubble distance affects their shape, size, and jet formation. The Boundary Integral Method (BIM) with a novel local smoothing technique is employed. Critical parameters including jet velocity, bubble centroid movement, bubble radius, and collapse time are computed for each bubble to understand their interaction dynamics comprehensively. The velocity vector field and pressure distribution surrounding the bubbles are analyzed, providing detailed insights into the fluid dynamics. The findings demonstrate that inter-bubble distance significantly influences their interaction and overall behavior. These results advance the understanding of bubble dynamics near rigid boundaries, with potential applications across various scientific and engineering disciplines. [ABSTRACT FROM AUTHOR]

We present algorithms for computing strongly singular and near-singular surface integrals over curved triangular patches, based on singularity subtraction, the continuation approach, and transplanted Gauss quadrature. We demonstrate the accuracy and robustness of our method for quadratic basis functions and quadratic triangles by integrating it into a boundary element code and solving several scattering problems in three dimensions. We also give numerical evidence that the utilization of curved boundary elements enhances computational efficiency compared to conventional planar elements. [ABSTRACT FROM AUTHOR]

This study proposes a numerical approach aimed at mitigating electromagnetic field intensities at ground level generated by overhead power lines. The methodology integrates the boundary element method for field evaluation with the ellipsoid method for field optimization, while adhering to critical design and safety constraints. The optimized power line configurations, derived from this integrated approach, achieved significant reductions in both electric and magnetic field magnitudes at ground level without compromising any specified constraints. Moreover, the research findings demonstrate the robustness, efficiency, and practical applicability of the proposed methodology in the design of optimized power lines, offering potential for increased power transfer capability, and decreased environmental and health impacts. [ABSTRACT FROM AUTHOR]

This study proposed an array of bottom-standing breakwaters (BSBs) in the presence of an oscillating water column (OWC) for a better understanding of physical mechanisms, under the framework of a linearized potential flow theory. The free water regions are provided between the multiple BSBs to utilize the gap resonance for energy extraction by OWC. The multi-domain boundary element method is adopted to conduct the parametric study, and the validation of the proposed model is presented. The effect of BSB physical properties, OWC, and incident wave properties are reported on the variation of OWC efficiency, radiation susceptance, conductance, force on the wall, and wave reflection by BSBs against the relative wave frequency and water depth. A comparative study on the variation of coefficients is presented between three types of BSB and flat seabed. The higher number of BSBs enhances the intensity of harmonics and subharmonics of coefficients and strengthens the harmonic trough of efficiency. The Bragg reflection by multiple BSBs diminishes the efficiency of OWC for particular wavelength, and the Bragg peak is suppressed by adopting the permeable property for BSBs. The enlargement of OWC efficiency toward the higher frequencies is observed with an increase in BSB height, width, and chamber length. This study suggests a pair of BSBs with a chamber length equal to water depth for optimal efficiency. Overall, the seaside inclined lip-wall, moderate chamber length, and double BSBs are recommended to diminish the Bragg peak (nearly 18%) and extract the maximum renewable energy for a wider frequency, from the OWC device against the incident waves. [ABSTRACT FROM AUTHOR]