Reference Configuration Research Articles

Utilizing physics‐augmented neural networks to predict the material behavior according to Yeoh's law

AbstractThis article discusses physics‐augmented neural network approaches in the field of hyperelastic material modeling. Physical conditions such as objectivity, material symmetry, or a stress– and energy‐free reference configuration are considered in the construction of the neural networks. In addition, a new approach for stress normalization is proposed. The neural network is used to learn the behavior of Yeoh's constitutive model with sparse data. Finally, the trained networks are incorporated into a three‐dimensional finite element framework and compared with the classical material model in terms of accuracy. The paper demonstrates the ability of physics‐augmented neural networks to model hyperelastic materials using a small amount of data that could be generated by experiments. Compared to the classical constitutive laws of Yeoh's model, our trained material showed no material instabilities that could occur due to poorly chosen material parameters.

The Cycle 46 Configuration of the HARMONIE-AROME Forecast Model

The aim of this technical note is to describe the Cycle 46 reference configuration of the HARMONIE-AROME convection-permitting numerical weather prediction model. HARMONIE-AROME is one of the canonical system configurations that is developed, maintained, and validated in the ACCORD consortium, a collaboration of 26 countries in Europe and northern Africa on short-range mesoscale numerical weather prediction. This technical note describes updates to the physical parametrizations, both upper-air and surface, configuration choices such as lateral boundary conditions, model levels, horizontal resolution, model time step, and databases associated with the model, such as for physiography and aerosols. Much of the physics developments are related to improving the representation of clouds in the model, including developments in the turbulence, shallow convection, and statistical cloud scheme, as well as changes in radiation and cloud microphysics concerning cloud droplet number concentration and longwave cloud liquid optical properties. Near real-time aerosols and the ICE-T microphysics scheme, which improves the representation of supercooled liquid, and a wind farm parametrization have been added as options. Surface-wise, one of the main advances is the implementation of the lake model FLake. An outlook on upcoming developments is also included.

Analytical assessment of suspension bridge's 3D curved cable configuration and cable clamp pre-installation angle considering the main cable torsional and flexural stiffnesses

For a suspension bridge with a spatial cable system, the 3D curved main cable undergoes large lateral and torsional deformations during construction, which increases the difficulty of construction control. If using the traditional ideal flexible cable assumption, the torsional deformation cannot be analyzed. Therefore, incorporating the main cable's torsional and flexural stiffnesses in shape-finding analysis remains highly challenging. This study develops an analytical method for determining the target configuration of the main cable by applying the multi-segment catenary method and the Cosserat rod model. The closed-form solution of the geometrically exact force-displacement-strain relationships is derived, comprehensively considering the tension, shear, bending, and torsion of the main cable, as well as the initial curvatures and axial strains in the reference configuration. Then a two-layer shape-finding framework is established, with the first layer being recursive calculations of the cable shape and the second layer being numerical calculations of the nonlinear governing equations using the Levenberg-Marquardt method. Furthermore, a novel method for calculating the pre-deflection angle of the cable clamp in the free cable state is presented for the first time. A classic cantilever model and a suspension bridge with the spatial main cable are studied to investigate the accuracy of the proposed algorithms. Numerical results indicate that when the spatial main cable is twisted, the bottom edge of the cable cross-section moves outward along the transverse direction of the bridge. The torsion of the main cable includes both elastic deformation and rigid body displacement caused by the bidirectional bending effect. At the mid-span, the torsional angle of the main cable cross-section is 10.088°, and the pre-deflection angle of the cable clamp at the mid-span should be set to 10.851°. Moreover, the target configuration is highly sensitive to the flexural and torsional stiffnesses of the main cable while the effect of shear deformations on cable configurations can be ignored.

Comparative analysis of Zero Pressure Geometry and prestress methods in cardiovascular Fluid-Structure Interaction

Background and Objective:Modelling patient-specific aortic biomechanics with advanced computational techniques, such as Fluid–Structure Interaction (FSI), can be crucial to provide effective decision-making indices to enhance current clinical practices. To effectively simulate Ascending Thoracic Aortic Aneurysms (ATAA), the stress-free configuration must be defined. The Zero Pressure Geometry (ZPG) and the Prestress Tensor (PT) are two of the main approaches to tackle this issue. However, their impact on the numerical results is yet to be analysed. Computed Tomography Angiography (CTA) and Magnetic Resonance Imaging (MRI) data were used to develop patient-specific 2-way FSI frameworks. Methods:Three models were developed considering different tissue prestressing approaches to account for the reference configuration and their numerical results were compared. The selected approaches were: (i) ZPG, (ii) PT and (iii) a combination of the PT approach with a regional mapping of material properties (PTCAL). Results:The pressure fields estimated by all models were equivalent. The estimation of Wall Shear Stress (WSS) based metrics revealed good correspondence between all models except the Relative Residence Time (RRT). Regarding ATAA wall mechanics, the proposed extension to the PT approach presented a closer agreement with the ZPG model than its counterpart. Additionally, the PT and PTCAL approaches required around 60% fewer iterations to achieve cycle-to-cycle convergence than the ZPG algorithm. Conclusion:Using a regional mapping of material properties in combination with the PT method presented a better correspondence with the ZPG approach. The outcomes of this study can pave the way for advancing the accuracy and convergence of ATAA numerical models using the PT methodology.

Phase Field Coupled Finite Deformation Plasticity Formulation of Ductile Fracture With Nonlinear Kinematic Hardening and Modified Energy Release Function

ABSTRACTA ductile damage theory is presented by coupling the covariant formulation of finite deformation plasticity with the phase field modeling of fracture, including kinematic hardening for the ductile response of the materials. A phase field coupled nonlinear kinematic hardening equation is proposed in the reference configuration having equivalent representation through the Lie derivative of the kinematic hardening tensor by push‐forward operation in the spatial configuration, thus ensuring the satisfaction of frame invariance. To capture the correct physical response of the material by the phase field evolution equation, the fracture driving function, that is, the difference between the sum of elastic and plastic energies and threshold energy, after the damage initiation is modified by an energy release controlling function, which is an empirical relation of equivalent plastic strain. In defining the energy release controlling function, well‐defined points with physical significance in the experimental load versus displacement curve are used. To simulate the response of the material in relatively large time steps, a modified staggered scheme is presented, evaluating the fracture driving and energy release controlling functions from the previous converged step and using the updated phase field variable in the weak form of the momentum balance equation. To quantify different material parameters from available experimental results in the literature, the developed phase field coupled elasto‐plastic model uses a neural network optimization procedure consisting of neural network training together with optimization in MATLAB and finite element model evaluation in Abaqus user element subroutine UEL. Model capabilities are demonstrated by simulating the crack propagation in complex 3D geometries such as the second and third Sandia Fracture Challenges.

Optimizing Energy Yield and Economic Benefit of Renewable Energy Technologies for Urban Mediterranean Dwellings

Mediterranean European cities are characterized by high population density and limited space for large-scale implementation of renewable energy installations. This paper addresses the optimization of renewable energy installations in Mediterranean dwellings with the scope of increasing their energy contribution and cost-effectiveness. In a case study for Malta, the three technologies studied were solar photovoltaics, solar water heating, and heat pump water heating. Technical and economic analyses were performed on a number of reference configurations using Polysun software (version 2022.8). Sensitivity analyses were also conducted to study the impact that different technical and economic factors have on the performance of the configurations considered. Finally, comparisons were made between the techno-economic results obtained from the reference and sensitivity analyses. Based on data collected, the presence of renewable energy source (RES) technologies in the residential sector of Malta was characterized and correlated with the types of dwellings considered. Among the results obtained, it was found that although a solar RES installation may experience some shading, this does not mean that it is rendered economically unfeasible. Moreover, from the simulations conducted, electrical energy storage technology was considered as too premature unless strongly subsidized, making economic sense only in specific circumstances. On the other hand, although heat pump water heating technology is also relatively modern, it was concluded to be the most beneficial in terms of both energy yield and economic benefit, generally speaking. Furthermore, it was determined that in a higher occupancy dwelling, solar water heating (SWH) and heat pump water heating (HPWH) result in considerably more attractive energy savings.

The mitigation of airframe noise using a Krueger flap as a leading-edge device in a high-lift configuration

High-lift device is a potent airframe noise contributor. The conventional slat, commonly used in a high-lift device, is known as one of the dominant noise sources. Here, we combine an experimental and a numerical approach to investigate the noise generation of a conventional slat and two Krueger flaps as leading-edge devices in a high-lift configuration. To reduce the computational cost, a short span of the entire high-lift device is selected as the focusing region for scale-resolving and acoustic computations using Improved Delayed Detached Eddy Simulation (IDDES) coupled with the Ffowcs-Williams and Hawkings (FWH) analogy. Simulation results show that turbulent cross flows induce slightly lower-level noise spectra at frequencies less than 300 Hz when the two spanwise sides of the FWH permeable integral surface are closed. Wind-tunnel test results show that the reference and optimal Krueger configurations effectively attenuate the dominant tone of the conventional slat by 4 and 6 dB, respectively. Besides, the optimal configuration is very effective in noise reduction in a wide frequency range. However, the reference Krueger configuration increases the noise level by 0 − 4 dB at frequencies exceeding 5, 500 Hz. Overall, the optimal Krueger configuration is a good choice for high-lift device noise mitigation.

Computing whole embryo strain maps during gastrulation

Gastrulation is a critical process during embryonic development that transforms a single-layered blastula into a multilayered embryo with distinct germ layers, which eventually give rise to all the tissues and organs of the organism. Studies across species have uncovered the mechanisms underlying the building blocks of gastrulation movements, such as localized in-plane and out-of-plane epithelial deformations. The next challenge is to understand dynamics on the scale of the embryo: this requires quantifying strain tensors, which rigorously describe the differences between the deformed configurations taken on by local clusters of cells at time instants of observation and their reference configuration at an initial time. We present a systematic strategy for computing such tensors from the local dynamics of cell clusters, which are chosen across the embryo from several regions whose morphogenetic fate is central to viable gastrulation. As an application of our approach, we demonstrate a strategy of identifying distinct Drosophila morphological domains using strain tensors.

Coupled torsion and inflation of functionally graded and residually stressed Mooney–Rivlin hollow cylinders

Functionally graded structures have material properties continuously varying in one or more directions. Examples include human teeth, sea shells, bamboo stems, and mammal organs in which the varying volume fraction and orientation of fibers optimize their functionalities. Here we analytically study large deformations due to combined torsion and inflation of residually stressed and radially graded Mooney–Rivlin hollow circular cylinders to provide insights into how grading their material moduli according to a power law function of the radius can be advantageously used. We simulate residual stresses in a thin wall hollow cylinder by inverting it inside out and in a thick wall cylinder by assuming that a longitudinal wedge opening parallel to the cylinder axis is closed by deforming it axisymmetrically. It is found that positive integer values of the power law exponent are generally advantageous but its negative values can have deleterious effects on stress distributions. Furthermore, a hollow cylinder with residual stresses generated by one of the foregoing methods in the reference configuration should be modeled as orthotropic rather than transversely isotropic for subsequent deformations. The analytical solutions provided here should help numerical analysts verify their algorithms for large deformations of rubber-like materials that are modeled by the Mooney–Rivlin relation, and design engineers for exploiting the radial gradation of the two material moduli to reduce structure’s mass without sacrificing its performance.

A 3D finite deformation constitutive model for anisotropic shape memory polymer composites integrating viscoelasticity and phase transition concept

The phase transition theory of shape memory polymers (SMPs) often involves a phenomenological assumption that the reference configuration of the newly transformed phase deviates from that of the initial phase. This distinction serves as a crucial mechanism in the manifestation of the shape memory effect. However, elucidating the precise definition of the reference configuration of the transformed phase poses a significant challenge in the formulation of the constitutive model. To tackle this challenge, a three-dimensional (3D) finite deformation constitutive model incorporating effective phase evolution for SMPs has been developed. This model merges insights from the classical viscoelastic framework with the phase transition theory. The anisotropic thermo-viscoelastic constitutive model is further developed by introducing hyperelastic fibers, which integrate the anisotropy of the fibers into a continuous thermodynamic framework through structure tensors. Implemented within the ABAQUS software via a user material (UMAT) subroutine, the proposed model has been meticulously validated against experimental data, showcasing its prowess in simulating stress-strain responses and shape memory characteristics of SMPs and their composites (SMPCs). This innovative model stands as an invaluable instrument for the design and of sophisticated SMP and SMPC structures.

Experimental study on the suppression of inlet blockage in rotating detonation combustor by porous-wall

The rotating detonation combustor (RDC) is renowned for its ability to provide substantial pressure gains. Nonetheless, during the stable operation of the RDC, the high-pressure rotating detonation wave (RDW) at the combustor inlet induces an increase in upstream chamber pressure, ultimately compromising engine stability and performance. To fully harness the performance advantages of the turbine-based continuous rotating detonation engine (TBCRDE) while maintaining engine stability, a porous-wall RDC has been developed to alleviate intake blockage and mitigate upstream chamber pressure rise. The operating modes, pressure rise characteristics, and performance parameters of both the porous-wall RDC and the reference configuration were systematically evaluated across varying air flow rates and nozzle designs. This analysis concentrated on the operational characteristics of the porous-wall RDC and its mechanisms for suppressing upstream chamber pressure rise. The findings reveal that the porous-wall RDC significantly extends the stable operating range and effectively reduces upstream chamber pressure rise by minimizing intake blockage. Specifically, the stable operating range is enhanced by 50 % at an outlet area ratio of 0.33, with stable rotating detonation combustion achieved at an outlet area ratio of 0.25. At an air flow rate of 1 kg/s and an outlet area ratio of 0.33, the chamber pressure rise is optimally suppressed, demonstrating a maximum reduction of approximately 16.4 %. The total pressure recovery coefficient of the combustor was analyzed, taking into account both intake loss and combustor pressure gain capabilities, and the propulsion performance of the two configurations was compared. The porous-wall RDC effectively reduces intake loss while slightly diminishing combustor pressure gain capability, resulting in a marginal increase in the total pressure recovery coefficient. Although this leads to a slight reduction in propulsion performance during chamber pressure rise suppression, the overall engine matching environment benefits from enhanced matching stability. Consequently, other engine components experience a reduced performance decline. Therefore, the implementation of a porous-wall structure is anticipated to improve the overall propulsion performance of the engine.

Research on Quantum State Implementation Based on Topological Insulators

Abstract This paper first introduces the mainstream technology route of quantum computing. The analysis provides the role and advantages of topological insulators in quantum computing, such as providing stable quantum bits, enhancing the coherence and non-locality of quantum bits, and enabling the transmission of quantum information and entanglement allocation. This paper then proposes a quantum state implementation scheme based on Bi2Se3, based on the characteristics and advantages of the quantum Hall effect of topological insulators. It includes calculating the eigenstates of the Hamiltonian of topological insulators, obtaining the spatial distribution of wave functions, and generating a quantum bit platform based on topological insulators. A quantum state implementation system based on topological insulator (Bi2Se3) was constructed, and the system framework and reference configuration were provided. The solution presented in this article is an important research achievement in topological quantum computing, providing more possibilities for the implementation of feasible fault-tolerant quantum computer prototypes.

Impact of Future Low-Emissions Combustor Technology on Acoustic Scaling Laws

A first-of-its-kind examination of broadband noise associated with a far-term advanced low-emission aerocombustor concept is presented. Because of design trends and expected cycle changes for future aircraft propulsion systems, noise generated by sources in the combustor are expected to become of increasing significance for airport-community noise. The paper assesses the impact on legacy semi-empirical noise-prediction methods from the expected radical departures from current combustor operating conditions and designs, such as fuel/air distribution and flame anchoring techniques. Such methods are essential in system-level noise assessments at the preliminary design stage for advanced air transports to assure that overall environmental goals are met. Detailed unsteady pressure measurements, obtained in a fundamental combustion noise experiment using a combustor rig at relevant pressures and temperatures are analyzed. In addition to an advanced far-term low-emissions concept, a reference configuration with the test section arranged to model a modern combustor sector was also studied. For the test rig in the current-generation configuration, the measured broadband acoustic data are reasonably well described by the acoustic-power scaling laws used in legacy semi-empirical noise-prediction methods. For the future-advanced configuration, the legacy scaling laws, with some notable exceptions, provide correct trends, but with much less accuracy.

An existence result for accretive growth in elastic solids

We investigate a model for the accretive growth of an elastic solid. The reference configuration of the body is accreted in its normal direction, with space- and deformation-dependent accretion rate. The time-dependent reference configuration is identified via the level sets of the unique viscosity solution of a suitable generalized eikonal equation. After proving the global-in-time well-posedness of the quasistatic equilibrium under prescribed growth, we prove the existence of a local-in-time solution for the coupled equilibrium-growth problem, where both mechanical displacement and time-evolving set are unknown. A distinctive challenge is the limited regularity of the growing body, which calls for proving a new uniform Korn inequality.

Monolithic finite element modeling of compressible fluid‐structure‐electrostatics interactions in MEMS devices

AbstractThis work presents a monolithic finite element strategy for the accurate solution of strongly‐coupled fluid‐structure‐electrostatics interaction problems involving a compressible fluid. The complete set of equations for a compressible fluid is employed within the framework of the arbitrary Lagrangian–Eulerian (ALE) fluid formulation on the reference configuration. The proposed numerical approach incorporates geometric nonlinearities of both the structural and fluid domains, and can thus be used for investigating dynamic pull‐in phenomena and squeeze film damping in high aspect‐ratio micro‐electro‐mechanical systems (MEMS) structures immersed in a compressible fluid. Through various illustrative examples, we demonstrate the significant influence of fluid compressibility on the dynamics of MEMS devices subjected to constrained geometry and/or high‐frequency electrostatic actuation. Moreover, we compare the proposed formulation with the nonlinear compressible Reynolds equation and highlight that, particularly at low pressures and high fluid viscosity, the Reynolds equation fails to provide a reliable approximation to the complete set of equations utilized in our proposed formulation.

Dimension reduction and homogenization of composite plate with matrix pre-strain

This paper focuses on the simultaneous homogenization and dimension reduction of periodic composite plates within the framework of non-linear elasticity. The composite plate in its reference (undeformed) configuration consists of a periodic perforated plate made of stiff material with holes filled by a soft matrix material. The structure is clamped on a cylindrical part. Two cases of asymptotic analysis are considered: one without pre-strain and the other with matrix pre-strain. In both cases, the total elastic energy is in the von-Kármán (vK) regime ( ε 5 ). A new splitting of the displacements is introduced to analyze the asymptotic behavior. The displacements are decomposed using the Kirchhoff–Love (KL) plate displacement decomposition. The use of a re-scaling unfolding operator allows for deriving the asymptotic behavior of the Green St. Venant’s strain tensor in terms of displacements. The limit homogenized energy is shown to be of vK type with linear elastic cell problems, established using the Γ-convergence. Additionally, it is shown that for isotropic homogenized material, our limit vK plate is orthotropic. The derived results have practical applications in the design and analysis of composite structures.

Total Lagrangian smoothed particle hydrodynamics with an improved bond-based deformation gradient for large strain solid dynamics

Total Lagrangian Smoothed Particle Hydrodynamics (TLSPH) is one variant of SPH where the variables are described using the fixed reference configuration and a Lagrangian smoothing kernel. TLSPH elevates the computational efficiency of the standard SPH when no topological change is involved, and it alleviates the stability of SPH scheme with respect to tensile loading. However, instabilities associated with spurious mode, or hourglass/zero-energy mode, persists and often affects the simulation of solids undergoing extremely large strain. This work proposes an alternative formulation to compute deformation gradient with improved accuracy and therefore minimising the possibility of encountering the zero-energy mode. Specifically, we leverage the local discrete computation of bond-based (or pairwise) deformation gradient smoothed by the kernel. Additionally, the bond of a particle with itself is considered to preserve the polynomial reproducibility imposed by the kernel correction scheme. We showcase the convergence of the approach using a two-dimensional benchmark example. Furthermore, the accuracy, robustness, and stability of the proposed approach are assessed in various two- and three-dimensional examples, highlighting on the stability improvement that allows for solid dynamic simulations with more extreme elongation.

Reducing parasitic currents in acid-base flow batteries by decreasing the manifold cross-sectional area: Experiments and modelling

The Acid-Base Flow Battery is an innovative and sustainable electrochemical storage system storing energy in the form of salinity and pH gradients. However, parasitic currents via manifolds dramatically affect system by reducing its Round-Trip Efficiency (RTE).This work experimentally studies this phenomenon using a purposely designed methodology involving sticks placed in the manifold ducts. Various figures of merit were calculated to evaluate battery performance in the charge and discharge phases. A mathematical model was validated and applied to investigate the ionic parasitic currents. The results highlighted the importance of studying this phenomenon, as achieving a reduction in the parasitic currents caused a 25% increase in the net power and more than tripled the RTE compared to the reference configuration without sticks. Although reducing manifold diameter increases pumping losses, it was found to be anyway really beneficial for the process performance and paves the way for future, more suitable, battery designs.

Задача нелинейной теории упругости о растяжении и кручении составного цилиндра с предварительно напряжённым включением, содержащим винтовую дислокацию

The problem of large torsional and tension-compression deformations of a composite circular cylinder of incompressible Bartenev-Khazanovich material is considered. The cylinder contains a central circular cylindrical inclusion in which a concentrated screw dislocation is formed. It is pre-twisted and stretched (or compressed) along the axis and bonded to an unstressed external hollow cylinder. A single reference configuration is used when solving a problem for a composite body. This configuration is natural (unstressed) for the outer hollow cylinder and prestressed for the inner solid cylinder. The large deformation superposition theory is used to write the determining ratios of the material of the inner cylinder. The nonlinear theory of torsion of elastic cylinders containing a screw dislocation is used to solve the problem of the prestressed state of the internal inclusion. This theory is physically correct not for any models of isotropic elastic materials, but only for those for which the screw dislocation in the cylinder has a finite linear energy and creates a longitudinal force of finite value. The Bartenev-Khazanovich model belongs to this class. The problem for a composite cylinder is solved by a semi-inverse method. Using this method, it is reduced to nonlinear ordinary differential equations. The assumption of isotropy and incompressibility of the material makes it possible to find an exact solution to the problem.

Thermomechanical modeling in elastic body with corotated total Lagrangian SPH

In this paper, we propose a novel thermal deformation formulation for elastic bodies' thermomechanical simulation with total Lagrangian smoothed particle hydrodynamics (TLSPH), which employing fixed reference configuration. We utilize implicit corotated TLSPH as a base methodology to address tensile instability and enhance the robustness of simulation. The reference configuration of heat transfer model is updated, but the reference configuration of thermal deformation model is fixed like TLSPH. As particle's temperature is changed, the inter-particle distance in reference configuration is updated by using linear thermal expansion theory. Validation involved two basic cantilever beam loading cases and a thermomechanical analysis with heat-induced thermal deformation on a cantilever beam. The TLSPH simulation results were compared against Finite Element Method simulations and analytical solutions, demonstrating equivalent accuracy across all tests. This study indicates the potential for conducting a wide array of simulations involving thermal deformation using the TLSPH method, which efficiently supports parallel computing on an individual particle basis.