Geometric Boundary Conditions Research Articles

A Parameterized Prediction Method for Turbulent Jet Noise based on Physics-informed Neural Networks

Abstract Turbulent noise prediction is integral to fluid equipment design, and multiple simulations or experiments are often required for noise distribution under varying operating conditions during the design optimization process, which could be expensive. Recently, the Physics Informed Neural Networks (PINNs) method has emerged as an efficient machine learning method for solving parameterized partial differential equations with geometric shapes, boundary conditions, and equation parameters as variable parameters through a single training session without data. In this study, a parameterized prediction method is developed to predict turbulent jet noise based on PINNs without any training datasets. Both two-dimensional (2D) and three-dimensional (3D) jet flow problems are solved. The 2D problem is solved with the Reynolds number as a variable parameter, and the 3D problem is solved with the Reynolds number and nozzle eccentricity as variable parameters. The predicted results are in good agreement with those from conventional computational fluid dynamics (CFD), with average errors of 3% and 6% for the 2D and 3D flow and acoustic power fields, respectively. In terms of computational efficiency, the time required by the method for the three-dimensional problem with two variable parameters is only one-seventh of that of the traditional CFD method. This study demonstrates that for engineering noise scenarios with varying parameters, the method based on PINNs offers a more efficient parameterized predicting approach and is promising for future applications.

Thermoelastic damping in bi-layered micro/nanobeam resonators using the dual-phase-lag generalized heat conduction model

The existing analytical investigations on thermoelastic damping (TED) in laminated micro/nanobeam resonators have generally neglected the thermal axial force and rarely considered the time lagging in the heat transfer. However, laminated beams will very likely exhibit stretching-bending coupling deformation due to the deviation of the physical neutral surface from the beam mid-surface. Furthermore, the TED in layered beams has been predicted by using the energy rather than the complex frequency approach. In this presentation, TED in bi-layered micro/nanobeams is analyzed based on the Euler-Bernoulli beam theory and the dual-phase-lag (DPL) generalized heat conduction theory by considering the thermal axial force. Analytical solutions for the TED in bi-layered micro/nanobeams are developed by using both the complex frequency approach and the energy method. Numerical results are presented to examine the effects of the thermal axial force and DPL relaxation times on the TED in the laminated beam resonators for different physical and geometrical parameters, vibration modes and mechanical boundary conditions, which reveal that the thermal axial force will increase (decrease) the TED in metal/ceramic (ceramic/ceramic, metal/metal) bi-layered beams. The maximum underestimation for the TED due to neglecting the thermal axial force will reach about 7 % in Ag/Si beam and 15 % in Cu/Si3N4 beam. The DPL effect on the TED is closely related to the material properties of the laminas and their volume fractions. For the Ag/Si beam with the thickness less than 1nm, influence of the DPL relaxation on the TED becomes significant which changes continuously from the negative contribution to the positive one with the increase in the volume fraction of the Si from 0 to 1. However, the DPL effect can be ignored in the bi-layered beams with micrometer size.

Numerical Analysis of Enhanced Subcooled Boiling Heat Transfer in a Twisted Tri-Lobed Tube

This study presents a detailed investigation of subcooled boiling phenomenon in a twisted tri-lobed tube, aiming to elucidate its role in tube design and application in thermal management systems. Integrating the Eulerian two-fluid model with the RPI wall boiling model, this study examines the influence of geometric parameters and boundary conditions in a twisted tri-lobed tube on heat transfer. Following validation with experimental data, the study spans a range of mass flux G=500-800 kg/(m²∙s), inlet subcooling ΔTsub,inlet=25-55 K, heat flux qw=0.3-0.6 MW/m², and outlet pressure Poutlet=5-8 MPa. Results show that increasing the minor radius (r) and straight segment length (l) and decreasing the transition radius (R), boosts secondary and helical flows but does not significantly affect the increase in wall void fraction. Furthermore, elevating the wall heat flux and outlet pressure, coupled with decreasing the inlet subcooling degree and mass flow flux, promotes subcooled boiling, thereby enhancing the average void fraction and convective heat transfer coefficient. Significantly, reducing ΔTsub,inlet to 25 K allows the performance evaluation criterion (PEC) of the twisted tri-lobed tube to reach 2.18. The methodologies and findings of this study contribute significantly to a deeper understanding of subcooled boiling process in a twisted tri-lobed tube.

Investigating the Impact of Various Binder Contents and Compression on Graphite Electrode Thickness Change Measurements

Volume change of active materials during the insertion of Li+-ions into the electrode’s host structure in lithium-ion batteries (LiBs) has become an increasingly researched topic. Reversible and irreversible thickness changes occur during operation because of active material volume change upon lithiation/delithiation and SEI growth. In LiBs, particularly the volume change of the negative active material can cause mechanical disintegration of the composite coating [1], causing loss of active material. LiBs are usually operated in a compressed state maintained by geometrical boundary conditions to ensure uniform contact between electrode layers. Therefore, the thickness changes can cause increased stack pressure and, subsequently, microstructural changes [2] and thus affect the performance and lifetime of the battery [3]. To better understand the aforementioned phenomena, accurate thickness measurements are required.Measuring the thickness change of a cell stack does not provide accurate information about the individual thickness change of the two electrodes. Therefore, single-electrode electrochemical dilatometry (ECD) can help to better understand the impact of the individual electrodes on cell stack thickness change. Due to the common use of a commercially available setup (EL-Cell, ECD-3-nano, Germany) in literature, most ECD experiments were conducted at a pressure of ~ 16 kPa onto a Ø10 mm working electrode (WE). Only in some publications higher pressures > 0.1 MPa were applied during single electrode measurements [4]. The applied pressure in lab-scale coin cell setups and state-of-the-art LiBs is usually significantly higher (0.1 – 0.5 MPa) than that of single-electrode ECD investigations. Therefore, the question arises whether the pressure has an impact on the measured thickness change.Thus, this work integrates a wave spring washer into a commercially available single-electrode ECD Setup (ECD-3-nano, El-Cell GmbH, Germany) to apply additional pressure onto the WE, without requiring geometrical modifications of the setup. The integration of the wave spring washer increases the applied pressure from 16 kPa to > 100 kPa. Graphite electrodes with different binder types and contents are investigated since distinct measurement artifacts were observed for electrodes with certain binder compositions in preliminary experiments. Electrodes without additional pressure show a first-cycle lithiation thickness increase of up to 30% (see Figure 1), which is much higher than the active material volume change of graphite obtained from XRD data [5] would suggest. For all examined electrodes at lower pressure the first and tenth cycle lithiation thickness change is more than 50 % higher compared to the setup at high pressure. The mechanism causing the discrepancy between measurements at the two pressure levels is identified as the curvature of the electrode edges at low pressures present in commercially available ECDs. Therefore, the setup at increased pressure enables a meaningful investigation of the influence of the binder content on irreversible and reversible thickness change for the electrodes under investigation using more realistic mechanical boundary conditions. Measurements show that irreversible thickness change decreases with increasing binder content. Possibly the higher binder content helps to prevent restructuring of the particles during cycling due to higher mechanical strength of the electrode. Delithiation thickness change is similar among electrodes with normal to high binder contents. Only electrodes with a very low binder content have a significantly lower reversible thickness change.Overall, this study shows that the influence of pressure onto the WE should be considered for future ECD-experiments and setups. This work presents an easy to implement solution to apply additional pressure onto the WE for a common commercially available ECD-setup.

Susceptibility of hydraulic structures to internal erosion: modeling of suffusion process

Internal erosion is a primary cause of hydraulic structure failure, manifesting as two key phenomena: piping erosion and suffusion. These processes differ in their geometrical and hydraulic boundary conditions, resulting in varying levels of failure risk. Piping erosion is the more hazardous and rapid process, often leading to immediate failure if not promptly addressed. In contrast, suffusion gradually alters the permeability of the medium, potentially culminating in failure after a prolonged period of development. In this study, we propose a model for suffusion based on Darcy’s law, Papamichos' erosion law, and Einstein's viscosity evolution relation. The model describes the temporal evolution of the average porosity in the porous medium, the concentration of eroded particles in the fluid, and the mass of particles eroded, while highlighting the impact of hydraulic and mechanical parameters, such as the erosion coefficient and maximum porosity, on this evolution. The numerical solution is obtained using the finite difference method, with the sample discretized into elementary layers. For discretization, an explicit off-centered scheme was adopted. The simulation results reveal that suffusion is strongly influenced by soil hydraulic and mechanical parameters, particularly the erosion coefficient (λ) and final porosity (Ømax).

Modified Easley formula for elastic critical global shear buckling stress of corrugated steel webs considering real boundary conditions

The real juncture between corrugated steel webs (CSWs) and flanges follows a multi-segmented line, distinct from that of flat steel webs. Classic methods may yield significant deviations in predicting the elastic global shear buckling capacity of CSWs of various scales due to their failure to consider real boundary constraints. Therefore, a universally applicable formula for calculating the elastic critical global shear buckling stress of CSWs, which accounts for real boundary conditions, is proposed. This formula is pertinent to both large-scale engineering CSWs and small-scale testing CSWs. This study commenced with a comprehensive reassessment of the elastic global shear buckling calculation method. Subsequently, the influence of geometric parameter ratios on the elastic critical global buckling stress was examined. The primary parameter was identified and employed to improve the global buckling coefficient. The proposed calculation method was validated using different corrugation configurations, including 1000-type, 1200-type, 1600-type, 1800-type, and 2000-type CSWs, as well as other CSWs used in experimental settings. These results were compared with those obtained from other reference methods. Findings indicate that the accuracy of the classic theoretical method is affected by variations in both boundary conditions and geometric dimensions due to the constraint effect of real boundary conditions. Under the real boundary conditions, the elastic critical global shear buckling stress of CSWs with simply supported boundary conditions is close to that of CSWs with consolidated boundary conditions. The ratio of web height to corrugation depth primarily affects the elastic global shear buckling capacity, which decreases as the ratio increases. The Easley formula can be modified based on the web height to corrugation depth ratio. Comparisons of numerous numerical and theoretical results reveal that the proposed calculation method exhibits commendable computational precision. In comparison to alternative formulas, the proposed method demonstrates enhanced consistency for calculating CSWs with varying geometric dimensions and boundary conditions, thereby demonstrating its favorable applicability. These conclusions provide valuable reference for the shear design of CSWs.

Knowledge-based model generation for aircraft cabin noise prediction from pre-design data

The climate targets set out in the “European Green Deal” call for the consideration and implementation of climate-friendly propulsion concepts and sustainable fuels in future aircraft configurations. This puts the use of very efficient propeller engines into the focus of aircraft design. However, these pose major challenges, especially to cabin acoustics, due to high, tonal sound pressure levels on the fuselage. The design of noise control measures requires the competence to predict the resulting interior noise as early as possible in the design process of the vehicle. This requires a high level of geometric and structural detail regarding the fuselage structure and cabin components. With increasing frequency range, the necessary structural details also increase, which have to be resolved in the simulation models due to the associated decreasing structural wavelength. Especially in the context of aircraft pre-design, there is usually not enough information available for a detailed vibro-acoustic modeling of the fuselage and cabin components, which allows a meaningful prediction of the vibrations and thus the cabin noise. Therefore, the knowledge-based tool Fuselage Geometry Assembler (FUGA) is developed for the targeted enrichment of preliminary design data with knowledge for detailed numerical analyses. This paper describes the knowledge-based geometry and model generation in FUGA, which can consider the necessary (increasing) level of detail for the vibro-acoustic prediction already in the preliminary design. For this purpose, aircraft data sets in the preliminary design data format Common Parametric Aircraft Configuration Schema (CPACS) form the modeling basis. Originating from the aircraft preliminary design, these initially describe the outer shell of the vehicle and are extended by detailed structural information that defines the geometric boundary conditions for component placement in cabin design. For the cabin components, the open-source geometry kernel Open Cascade Technology (OCCT) is used to provide geometries at the level of detail required for subsequent analyses. The geometry models are then discretized in open source (e.g. Gmsh) or commercial meshers and further used for numerical analysis. Finally, the prediction of cabin noise is demonstrated as a Proof of Concept using the example of a short-haul propeller-driven aircraft and the feasibility of the proposed method is indicated by investigating the sensitivity of resulting simulation models to the fuselage skin thickness.

Development of a novel circular saw blade substrate with high stiffness for mitigating vibration noise and improving sawing performance

The circular saw blade substrates featuring a large diameter-thickness ratio and multiple saw teeth are increasingly required to accomplish the first or second machining tasks with high efficiency in sawing operations. However, the weak bending stiffness of this substrate can easily cause intense vibrations and harsh noises, while its special structure characteristics pose further challenges to vibration mitigation. This research develops a novel circular saw blade substrate with high bending stiffness to improve dynamic stability. Taking the geometric features and boundary conditions of the substrate into account, a transverse vibration differential equation for high-speed sawing operation is established to investigate the relationship between the mode shapes of the substrate and the stability performance of the sawing system. Theoretical analysis shows that the laminated structure can enhance the bending stiffness. Using this finding, the novel substrate is designed equipped with an m-shaped damping cavity and a laminated core structure, and its dynamic performance is quantified by the complex modulus law and thin-plate vibration theory. Then, the optimized design of the relevant materials and geometrical dimensions of the novel substrate is executed by the pseudo-density method. Finally, the novel substrate is fabricated and then certified by sawtooth point dynamics tests and sawing experiments. The experimental results show that the sawing quality of the novel substrate is improved by more than 50.2 %, and the sawing vibration and weighted sound pressure level are reduced by about 35 % and 12 dB(A), respectively, compared with the conventional one.

Three-dimensional elastoplastic post-buckling analysis of functionally graded plates using a novel meshfree Tchebychev-radial point interpolation approach

This paper presents a three-dimensional (3D) analysis of the post-buckling behavior of functionally graded (FG) plates for the first time using an elastoplasticity-based meshfree formulation. A novel 3D Tchebychev-radial point interpolation approach, which combines radial basis functions with Tchebychev polynomials, is developed to solve the nonlinear post-buckling problem. The incremental plastic deformation is modeled by the Prandtl–Reuss flow rule along the isotropic hardening von Mises criterion. The governing equations are derived using the principle of virtual work by considering the 3D full Green–Lagrange strain components. The Newton–Raphson technique along with the arc-length method is used to determine post-buckling equilibrium paths of FG plates. The effective elastoplastic properties of the functionally graded material are assessed by exploiting the homogenization method, named Tamura–Tomota–Ozawa (TTO) model. It has been demonstrated that the accuracy of the solution is improved by incorporating Tchebychev polynomials into the radial point interpolation method (RPIM) shape function, and the stability and robustness of the results are independent of variations in the shape parameter. Furthermore, it is confirmed that TRPIM, with a slightly higher CPU time compared to RPIM, exhibits a higher convergence rate. The excellent agreement of the results with those existing in the literature shows that the proposed meshfree method can be used as a robust and accurate numerical tool to predict the elastoplastic post-buckling behavior of FG plates. Further numerical assessments indicate that post-buckling paths are significantly affected by factors such as geometric parameters, material gradient, loading ratio, and boundary conditions (BCs).

STATIC BENDING RESPONSE OF COMPOSITE PLATES RESTING ON VARIABLE ELASTIC FOUNDATIONS

This article introduces a finite element approach for examining the static bending behavior of composite plates. The method considers the variable mechanical characteristics of plates and utilizes an elastic foundation with varying stiffness values. The plate's calculation expressions and equilibrium equations are derived using the new style shear deformation theory. The article uses a mesh composed of four-node rectangular components to solve the equilibrium equation. Each node in the mesh has six degrees of freedom. The solution's dependability and convergence are confirmed by comparing it with previously published findings. Based on this premise, the study presents numerical findings that examine how various geometric factors, materials, boundary conditions, and elastic foundations affect the static bending behavior of composite panels. This research is a great resource for engineers, providing excellent guidance for the design, production, and utilization of these structures in real-world applications.

A universal simulation model of the continuous pipe rolling process on a controllably movable mandrel.

To study the technological process of rolling solid and hollow round profiles, it is important to have a correct mathematical description of the patterns that determine the boundaries of the deformation zone. The article analyzed scientific works that examine the calculation of geometric parameters of the deformation zone during the rolling of solid and hollow round profiles in two-roll and multi-roll calibers. As a result of the analysis, a conclusion was drawn regarding the necessity of a more detailed description of the determination patterns for the geometric boundary conditions of the deformation zone. This led to the proposal of a universal method for determining the shape of the billet and the shape of the caliber groove, as well as the derivation of the equations for the roll surface and the boundary of the contact surface of the deformation zone for various rolling schemes. The developed method allows for an increase in the accuracy of calculating the energy-force parameters of the rolling processes, including continuous rolling, in the production of solid and hollow round profiles according to the circular–oval scheme in calibers formed by any number of rolls, thanks to the consideration of a sufficiently wide range of geometric features

Numerical simulations of temperature loads on multilayer Laue lenses

We present numerical simulations of the heat loads on novel diffractive X-ray optics, known as multilayer Laue lenses, exposed to high-intensity X-ray beams produced by an X-ray free electron laser (XFEL). These lenses can be used to focus XFEL beams to nanometer spots. The temperature distribution within the lens and temperature evolution as a function of incident pulse frequencies were calculated for two different lens geometries and several material pairs and material ratios of the MLLs. Simulations considered the special pulse structure of European XFEL with X-rays being delivered in pulse trains. After defining the geometric model, computational grid, material properties, and boundary conditions, a grid sensitivity study was carried out. We solved the transient heat energy transport equation in solids for mixed boundary conditions. The results of these simulations will help select materials and lens geometry for future XFEL experiments.

A novel method based on the calculus of variations to optimize the cooling passage configuration in thermal protection structure

A novel method based on the calculus of variations to obtain the optimization of cooling structure was developed in this work. The optimization of heat sink designs for better heat-dissipating effects has been researched substantially. However, the optimization of cooling passage configurations in thermal protection structures to improve the comprehensive heat transfer performance has remained a long-term interest and unsolved problem for researchers. Due to the intrinsic complexity, the laminar flow is usually considered before while the turbulent flow is seldom treated. It is valuable to provide timely and effective solutions to optimize the cooling structure, where the turbulent flow is involved, for practical use. A novel method to optimize cooling structure based on the calculus of variations has been developed to meet this need. The average temperature, temperature inhomogeneity, and coolant flow pressure drop were chosen as objective functions. The cooling channels can be established depending on the geometric and thermal boundary conditions of the structure, and then the quasi-three-dimensional simulation of the fluid/solid coupling field was calculated to get the temperature distribution of the cooling structure, the pressure drop, etc. Hence, this work explores the feasibility of combining coupled heat transfer and the calculus of variations to realize optimal cooling channels. By the novel method, the minimum objective function can be obtained.

Constraint-based analysis of heat transport and irreversibility in magnetic nanofluidic thermal systems

Purpose This paper aims to investigate the thermal performance of equivalent square and circular thermal systems and compare the heat transport and irreversibility of magnetohydrodynamic (MHD) nanofluid flow within these systems. Design/methodology/approach The research uses a constraint-based approach to analyze the impact of geometric shapes on heat transfer and irreversibility. Two equivalent systems, a square cavity and a circular cavity, are examined, considering identical heating/cooling lengths and fluid flow volume. The analysis includes parameters such as magnetic field strength, nanoparticle concentration and accompanying irreversibility. Findings This study reveals that circular geometry outperforms square geometry in terms of heat flow, fluid flow and heat transfer. The equivalent circular thermal system is more efficient, with heat transfer enhancements of approximately 17.7%. The corresponding irreversibility production rate is also higher, which is up to 17.6%. The total irreversibility production increases with Ra and decreases with a rise in Ha. However, the effect of magnetic field orientation (γ) on total EG is minor. Research limitations/implications Further research can explore additional geometric shapes, orientations and boundary conditions to expand the understanding of thermal performance in different configurations. Experimental validation can also complement the numerical analysis presented in this study. Originality/value This research introduces a constraint-based approach for evaluating heat transport and irreversibility in MHD nanofluid flow within square and circular thermal systems. The comparison of equivalent geometries and the consideration of constraint-based analysis contribute to the originality and value of this work. The findings provide insights for designing optimal thermal systems and advancing MHD nanofluid flow control mechanisms, offering potential for improved efficiency in various applications. Graphical Abstract

Multi-objective optimization of CO2 ejector by combined significant variables recognition, ANN surrogate model and multi-objective genetic algorithm

The ejectors are crucial in enhancing the efficiency of the CO2-based refrigeration cycle. Although the ejector can be optimized by experimental and computational fluid dynamic simulation to improve its performance, these methods are time-consuming and complicated. This research aims to present a fast and systematic approach for optimizing CO2 ejector by combining variance analysis, surrogate model, and non-dominated sorting genetic algorithm. Firstly, the key geometric structures affecting the performance of ejector were determined by variance analysis. Secondly, the influence of key geometric structures and boundary conditions on ejector efficiency and entrainment ratio was analyzed by using computational fluid dynamic simulation, and the database was generated. Next, the artificial neural network surrogate model was established to forecast the ejector performance. Finally, the non-dominated sorting genetic algorithm was involved to optimize the ejector for maximizing ejector efficiency and entrainment ratio. The results show that the efficiencies of the optimized ejectors are above 42%, and the entrainment ratios exceed 0.7. Compared with the basic model, the average efficiencies have increased about 13.20%. When the pressure lift is 0.7 MPa, the entrainment ratios of the optimized ejectors are 0.696 (−20 °C ≤ Te < −15 °C), 0.82(-15 °C ≤ Te < −5 °C), 0.60 (−5 °C ≤ Te < 5 °C) and 0.90 (5 °C ≤ Te < 15 °C), respectively. The above research demonstrates that the success of this approach in addressing time-consuming multi-optimization problems. It offers a fast and systematic approach for the multi-objective optimization of CO2 ejector as a valuable reference for engineering applications.

In-Plane Vibrations of Deep Sandwich Arches with Different End Conditions Based on a Logarithmic Shear Deformation Theory

This paper deals with the vibrational frequencies of deep sandwich arches to enhance their application domain and possibly use them for energy harvesting. The circular arch with porous nanocomposite core and titanium alloy face sheets having different end conditions is numerically analyzed. The middle core of the sandwich arch is made of a six-layered porous aluminum reinforced with graphene nanoplatelets. The kinematic equations are formulated in this study based on the higher-order shear deformation theory using a logarithmic function of radius. The effective properties of the nanocomposite media are modeled by employing the Halpin–Tsai modified rule. The equations of motion are determined by applying the principle of virtual displacement. The partial differential equations are reduced using the generalized differential quadrature technique to solving an algebraic eigenvalue problem. Novel numerical results are given to show the effects of geometrical parameters, material properties, and boundary conditions on the vibrations of deep sandwich arch.

An energy-balanced method for determining the optimized parameter of the incompatible generalized mixed element

A novel method for determining the optimized parameter of the four-node incompatible generalized mixed element is presented based on the equilibrium between strain energy and complementary energy. The presented energy formulations are derived from the generalized mixed variational principle, which contains an arbitrary additional parameter. The initial solutions expressed by the displacement field are firstly assumed for the description of the energy of each generalized mixed element. Then, the identical relationship between strain energy and complementary energy is subsequently expressed at element level, which includes the arbitrary parameter. At the same time, a formulation for determining the optimized parameter at element level is proposed. Several representative examples with varying geometrical parameters, boundary and loading conditions are used to validate this method. By contrasting with the results of generalized mixed elements with different parameter values and other traditional finite elements. The effectiveness of the presented method has been demonstrated. On one hand, by ensuring the strain energy and complementary energy remain consistent under both coarse and fine meshes, the optimized parameter can adjust the stiffness of the generalized mixed element, thereby enhancing its resemblance to the real elastic body. On the other hand, the generalized mixed element has the additional advantage of conveniently introducing stress boundary conditions, thereby satisfying the requirement for zero-conditions of shear stresses on the exterior surfaces of beams. The numerical results obtained by the proposed method are accurate and stable.

Investigation of mechanical behaviors of spoke-wheel cable structures through experimental and numerical analysis driven by digital-twin

Ascertaining the mechanical behaviors of large-scale space structures (e.g. spoke-wheel cable structure) is essential for guaranteeing their structural safety. This study proposed a digital-twin (DT)-based method for analyzing the mechanical behaviors of spoke-wheel cable structures. A spoke-wheel cable structure with a span of 6 m was used as a case study to validate the proposed method. The structural behaviors, such as cable forces and structural displacements under five loading conditions (i.e. dead load and dead load plus 3/10, 5/10, 8/10 or full-areal live load), were investigated experimentally and numerically. A comparative analysis was conducted to compare the results using the proposed method with the traditional method. Results show that the proposed DT method could help to update geometric details and boundary conditions of the twin model for ensuring effective numerical analysis. Moreover, the changing trends of general force for the same type of cables were basically the same under different loading conditions. Besides, the forces of upper spoke cables and inner-ring decreased under the action of live load, whereas the forces of lower spoke cables and inner-ring increased. The displacement directions of loaded and unloaded nodes were downward and upward, respectively, when subjected to uneven live loads. In addition, the vertical displacements of the outer nodes were greater than thoseof the inner ones. Furthermore, the cable forces and displacements of the structure changed more obviously under the action of asymmetric load. The established high-fidelity DT model could support effective numerical analysis of mechanical behaviors of large-scale space structures.

Aerothermoelastic flutter analysis of variable angle tow composite laminated plates in supersonic flow

A theoretical model is developed to investigate the aerothermoelastic flutter behavior of variable angle tow (VAT) composite laminated plates on elastic foundation in supersonic flow with general boundary conditions. The equations of motion of the VAT composite laminated plate are established by adopting the first-order shear deformation theory and the supersonic piston theory. The composite laminated plate is considered to be lying on an elastic foundation (such as a thermal protection shield) on one side and exposed to supersonic airflow on the other side. The displacement components of the structure are expanded into Chebyshev polynomials multiplied by the boundary characteristic functions to satisfy the geometric or natural boundary conditions. To validate the proposed theoretical model, a finite element (FE) model is also established by ABAQUS, and the numerical results fit well with that of the developed theoretical model. The effects of the boundary conditions, thermal loads, elastic foundations and laminate layouts on the flutter characteristics of the VAT composite plate are revealed and discussed in detail. This work can provide a reference for the dynamic design of the VAT composite laminates in the aerospace engineering.

Physics-informed neural network for solution of forward and inverse kinematic wave problems

The one-dimensional kinematic wave (KW) model (KWM) is widely used in surface water and water quality hydrology as well as for modeling the movement of traffic on long highways. The KW model involves a first-order nonlinear partial differential equation which is solved numerically for realistic geometric representation, input, and initial and boundary conditions. This paper developed a method to solve the partial differential equation using a neural network structure, called the physics-informed neural network (PINN). The PINN was applied to solve the one-dimensional nonlinear KWM for forward and inverse problems. To enhance the accuracy and convergence and to suppress the spurious oscillation at the steep front, a technique with redistributed collocation points as an improved algorithm of PINN was employed. To deal with the fractional order of the nonlinear advection term, a stop-gradient technique was proposed. For validation, the KWM for steady and unsteady overland flow, and open channel flow without lateral inflow was analyzed for the forward problem. For the inverse problem, the unknown Manning coefficient was correctly computed, demonstrating the capability of the proposed algorithm for the identification of KWM parameters.