Practical Numerical Model Research Articles

Research on the design and noise reduction performance of periodic noise barriers based on nested structure

The rapid development of highway transportation has led to a gradual deterioration of the sound environment along highways. The theory of periodic structures provides a new approach for the design of traffic noise barriers. However, the lack of practical numerical models and on-site experimental validation has hindered the widespread application of periodic structure sound barriers. This study investigates the noise reduction performance of nested structure periodic sound barriers. Results from semi-anechoic chamber tests demonstrate excellent wave attenuation at the air gap of the barrier, achieving a peak noise reduction of 16 dB without the addition of any sound-absorbing materials or treatment measures, particularly at local peaks in the highway noise spectrum. To enhance the noise reduction performance of nested structure periodic sound barriers, three optimization measures were explored: filling sound-absorbing materials inside the scattering elements, adding micro-perforated panels, and their combined effects. The results indicate that both porous sound-absorbing materials and micro-perforated panels can improve noise reduction effectiveness, especially outside the air gap. In the optimization design of nested structure periodic sound barriers, adding porous sound-absorbing materials inside the micro-perforated panels effectively enhances noise reduction within the air gap. Considering the abundance of abandoned w-beam guardrails in highway projects, which also meet the requirements of scattering elements, this study proposes the use of abandoned w-beam guardrails as scattering elements. This approach aligns with principles of cost-effectiveness and environmental sustainability, and it provides design guidance to promote the application of nested structure periodic sound barriers in traffic noise control.

Launch and recovery of a work class ROV through wave zone in small offshore service vessel

The deployment of remotely operated underwater vehicle (ROV) from a small offshore service vessel (OSV) based on single point mooring system (SPMS) method is recently adopted in offshore renewable energy sector. However, the tension spike in wire, also known as snap load, often occurs when the ROV passes through the wave zone in launching and lifting operation of deployment. In this study, a practical numerical model for predicting wire tension during launch and recovery of ROV is developed and validated by wave flume test of a 1:10 scaled model. The numerical simulations reveal that the ROV deployment at vessel stern along with an appropriate reduction of horizontal distance from the hull are reliable safety strategies for reducing wire tension. By adopting the new deployment strategy, the annual operational capacity can be expanded by approximately 6% when the safe operational limit of ROV under a significant wave height of 1.25 m. Based on the comprehensive numerical simulation, the newly developed safe operating envelope provides a further guidance for onboard ROV operation in the O&M of offshore wind farms.

Vibration response of ultra-shallow floor beam (USFB) composite floors

This paper examines the vibration response of the steel-concrete composite Ultra Shallow Floor Beam (USFB®) flooring system which incorporates asymmetric steel perforated beams to accommodate the concrete floor slab within the depth of the flanges while allowing reinforcement and/or service ducts to pass through the web openings. This is a lightweight flooring system that can accommodate long spans, thus becoming susceptible to floor vibrations due to external resonant dynamic loads. To investigate the influence of slab thickness and boundary conditions on the natural frequencies of the USFB flooring system, parametric studies are conducted using a finite element model and five floor spans. The model was first validated against an experimental test conducted by the authors. Emphasis is placed on the fundamental frequency to predict the possibility of resonance of this complex flooring system with typical human-induced dynamic loads in building structures. To further facilitate the practical numerical modelling and vibration analysis of buildings with USFB floors in standard commercial structural software, an analytical method of deriving equivalent isotropic plate properties is developed and its accuracy is numerically verified vis-à-vis with detailed ABAQUS models.

Practical Model for the Calculation of Lateral Electromagnetic Loads in Tokamaks at Asymmetric Vertical Displacement Events (AVDEs)

This paper describes a new practical numerical model for the calculation of lateral electromagnetic (EM) loads in tokamaks during asymmetric vertical displacement events (AVDEs). The model combines key features of two recently reported trial models while avoiding their drawbacks. Their common basic feature is the superposition of two patterns of halo current: one perfectly symmetric and another perfectly anti-symmetric. This model combines the following features that have not been combined before (a) a helically distorted halo layer wrapping around core plasma, and (b) halo-to-wall interception belts slipping along plasma-facing walls. This combination almost doubles the lateral net forces. An AVDE creates significant lateral net moments. Being relatively modest at VDEs, the lateral moments become a dominant component of EM loads at AVDEs. The model carefully tracks the balance of net EM loads (zero total for the tokamak), as a necessary condition for the consequent numerical simulation of the tokamak’s dynamic response. This balance is needed as well for the development of tokamak monitoring algorithms and simulators. In order to decouple from the current uncertainties in the interpretation and simulation of AVDE physics, the model does not simulate AVDE evolution but uses it as an input assumption based on the existing interpretation and simulation of AVDE physics. This means the model is to be used in a manner of parametric study, at widely varied input assumptions on AVDE evolution and severity. Parametric results will fill a library of ready-for-use waveforms of asymmetric EM loads (distributed and total) at tokamak structures and coils, so that the physics community may point to specific variants for subsequent engineering analysis. This article presents the first practical contribution to this AVDE library.

Numerical modelling of bridge deck reinforcement corrosion based on analysis of GPR data

AbstractThis study explores the impact of corrosion on Ground Penetrating Radar (GPR) responses through practical experiments and numerical modelling, focusing on rebar diameter reduction, corrosion product layer thickness, crack formation and corrosion product filling in vertical and transverse crack. Practical experiments involved GPR testing of reinforced concrete slab. By analyzing B-scans we identify areas with moderate and severe corrosion. Numerical modelling using the Finite Difference Time Domain (FDTD) Method to model GPR signal propagation in a concrete bridge deck with corrosion is applied. Key finding includes a significant 26.70% increase in reflected wave amplitude when corrosion product filling in vertical crack increased by 400%, highlighting its extensive effect on signal GPR propagation. Reduced rebar diameter led to a 9.79% amplitude decrease and a 0.06 ns arrival time delay. Increased corrosion product layer thickness primarily affected arrival time with a 0.06 ns extension but significantly amplified GPR signal amplitude. These findings offer insights for improving GPR based corrosion detection and assessment methods, leading to more robust systems for concrete bridge deck inspection and maintenance. This paper contributes to understanding how corrosion affects the signal that is detected by GPR. This information can be used to improve the way that we manage and assess corrosion in concrete bridge deck.

Comparative analysis of calculations in thin-walled structure design

This article focuses on reproducing normative calculation conditions through numerical methods and comparing these with outcomes obtained using specialized software for structural engineers. We analyse the basis of normative critical forces and stress values, including conditions of fixity, types of structures, and materials, and how these are represented in practical calculations and numerical modelling. The investigation is intended to enhance understanding between normative assumptions and their practical application in design, offering valuable guidelines for refining calculation methods.

Learning rate matters: Reexamining optimal power expansion planning with endogenized technological experience curves

The solution of an optimization-type power generation expansion planning model that endogenizes technology costs through the application of experience curves is highly dependent on the assumed values of the learning rate. Practical numerical models of this type derive a solution in which early diffusion of emerging technology, such as solar photovoltaic systems, leads to an intertemporal minimization of total electricity generation costs if the technology's assumed learning rate is above a particular boundary value; however, the principle behind this derivation is not well understood. This study aims to clarify the principle using a simple analytical model represented as an optimal control problem in addition to a numerical model. It identifies the factors influencing the solution as the discount rate and deployment rate at an initial time relative to the potential market share of the emerging technology. Analysis shows: (1) the higher the values of these two factors, the stricter the condition of learning rate required for the early diffusion of the technology to be optimal, holding other conditions constant; (2) the two factors have interaction effects on the optimal diffusion condition. Also, the study verifies the consistency of the results obtained from the analytical and numerical models.

Numerical Modelling of Traditional Timber Columns Resting on Stone Bases

ABSTRACT Columns in traditional timber structures are commonly seen resting on stone bases and are very important in resisting lateral loads. This paper numerically modeled the lateral resistance of the columns combined with experimental investigation. Different numerical models were developed, based on which sensitivity analyses were performed. A practical numerical modelling strategy was further proposed and verified. The analysis results indicated that instead of material properties and contact area, the columns’ lateral performance was much more sensitive to the variation of surface curvature at bottom surface. Without consideration of the surface curvature, the modeling error in the initial stiffness and peak load of a column was more than 607% and 8%, respectively. By best matching the load–displacement curves of tested column specimens, the optimal surface curvature was identified as 1/20306.5 mm−1. Then, a practical finite numerical model, characterized by the optimal curvature at the bottom surface, was proposed. This modelling method was validated by use of existing test results of traditional timber columns with different diameters and vertical compression loads. The modelling load–displacement curves agreed well with experimental curves both in terms of the initial lateral stiffness and peak load. Detailed simulation results based on the practical modelling strategy were presented and discussed.

Numerical modeling and field test of sonic crystal acoustic barriers.

The rapid development of highway traffic has gradually deteriorated the acoustic environment along the line. Sonic crystal theory provides new ideas for traffic acoustic barrier. However, the lack of practical numerical models and field test verifications has restricted the promotion and application of sonic crystal acoustic barriers (SCABs). In this study, a field test was conducted to study the noise reduction performance of SCAB. The SCAB exhibits excellent wave attenuation in the band gap, when compared with concrete acoustic barriers (CABs) along highways, the noise reduction performance in the band gap is improved by 0.5-2.1dB(A), especially at the local peak in the highway noise spectrum. However, from the perspective of total insertion loss, CAB performs better than SCAB in all distances in the protected area. Next, the 3D FEM model is established based on the highway site and validated by the measured results. Compared with the commonly used 2D model, the 3D FEM model is more practical for considering the top diffraction and ground reflection, which influence the noise reduction performance a lot and need to be considered. To improve the noise reduction performance of SCAB, three types of optimization measures are explored. The gradient combination of scatterers can effectively improve the noise reduction effect in the low-frequency band gap, especially the high- to low-gradient layout. Besides, not only the porous sound-absorbing material but also the microperforated plates can improve the noise reduction effect, especially outside the band gap. The larger perforation rates and smaller apertures of microperforated plate are preferred in SCAB. This work provides field test support and promotes the application of SCABs in traffic noise control.

Internal diffusion and re‐emission of leaked liquid ethyl acetate from mortar materials

AbstractAssuming the leakage of hazardous liquid chemicals in factories and chemical plants caused by natural disasters or human error, it is important to precisely estimate exposure risk and design appropriate evacuation plans and risk‐reduction measures. The exposure risk of indoor residents to leaked chemicals may be estimated using direct measurements or theoretical/numerical estimations of gas‐phase concentrations. Although mathematical models of gas‐phase concentration in the workplace are essential for predicting exposure concentrations at the design stage, practical models have not yet been fully established. We previously proposed practical numerical models to assess indoor gas‐phase concentration distributions after the accidental leakage of liquid chemicals using liquid toluene as a representative hazardous chemical. In this study, the leakage of liquid ethyl acetate, a commonly used organic solvent, into mortar flooring was reproduced in a small test chamber, and numerical analysis was performed. The results showed that the time history of the chamber exhaust concentration had a sharp peak and differed significantly from that of toluene. Three‐dimensional computational fluid dynamics (CFD) analysis incorporating practical ethyl acetate emission models reproduced the external and internal emission characteristics of leaked ethyl acetate on the mortar material. The models showed reasonable agreement with the experimental data.

Numerical Simulation of Hydraulic Characteristics of Spillway Tunnel with Gradually Expanding Outlet and Lower outlet height

Using a practical and efficient overall three-dimensional turbulent numerical model of the spillway tunnel, the numerical simulation of the hydraulic characteristics of the spillway tunnel with the gradually expanding outlet and lower outlet height is carried out. The calculation results show that when the gate is fully open, there is pressure flow in the whole tunnel of the spillway tunnel, and the flow state is stable; when the gate is not fully open and the water level is low, the flow state in the tunnel is unstable, and the free and pressure flow occur alternately. When the gate is at a small opening, the flip bucket raises the water level at the outlet, and the lower outlet height causes insufficient air supply in the cave, which is prone to cavitation. The lift distance is small, and it is easy to scour the slope of the hole. The lower outlet height at the outlet of the spillway tunnel further exacerbates the complexity of the hydraulic characteristics in the back arc section, which should be paid attention to during design and construction, and it is necessary to carry out hydraulic model test research.

Predictive environmental hydrogen embrittlement on fracture toughness of commercial ferritic steels with hydrogen-modified fracture strain model

In this work, a practical numerical model with few parameters was proposed for the prediction of environmental hydrogen embrittlement. The proposed method adopts hydrogen enhanced plasticity-based mechanism in a fracture strain model to describe hydrogen embrittlement. Fracture toughness degradation of three commercial steels SA372J70, AISI4130 and X80 in high pressure hydrogen environment were investigated. Firstly, governing equations for hydrogen distribution and material damage evolution was established. Hydrogen enhanced localized flow softening effect was coupled within fracture strain dependency on stress triaxiality. Then, the numerical implementation and identification process of model parameters was described. Model parameters of the investigated steels were determined based on experiment results from literatures. Finally, with the calibrated model, fracture toughness reduction of the steels was predicted in a wide range of hydrogen pressure. The prediction results were compared with experimental results. Reasonable accuracy was reached. The proposed method is an attempt to reach balance between physical accurate prediction and engineering practicality. It is promising to provide a simplified numerical tool for the design and fit for service evaluation of hydrogen storage vessels. • Hydrogen embrittlement prediction model with few parameters was proposed. • Identification of model parameters with a few support of experiments. • Simplified Fracture toughness prediction model with acceptable accuracy.

A practical numerical model for thin-walled steel connections and built-up members

The interaction between the cold-formed steel members and fasteners in a structural assembly often involves complex stress states, material plasticity, significant in-plane deformations and curling, rendering computational modelling of the resulting structural system challenging. In addition, the presence of initial geometric imperfections and the susceptibility of cold-formed steel members to local instabilities adds a further degree of complexity to the numerical modelling. The behaviour of bolted connections between cold-formed steel members has traditionally been assessed based on physical tests, though these can be time consuming and expensive. In this paper, a practical numerical approach to the simulation of bolted cold-formed steel connections, capturing all the key behavioural features including bolt preload, slippage and bearing, is introduced. Starting from a typical shell finite element (FE) model of a cold-formed steel plate, a small number of solid elements is introduced around the bolt holes, to allow accurate replication of the bolt-ply interaction, with contact pairs defined between the bolts and the surrounding material. An explicit dynamic solver is then employed to solve the geometrically and materially nonlinear problem, both with and without bolt slippage. Validation of the FE model is conducted using benchmark tests reported in the literature. It is shown that the proposed numerical method can accurately capture the structural behaviour of bolted cold-formed steel connections and cold-formed steel built-up sections, while being computationally efficient and numerically stable; the proposed approach is therefore recommended for the numerical modelling of cold-formed steel systems assembled using fasteners.

Practical Numerical Model for Wave Propagation and Fluid-Structure Interaction in Infinite Fluid

Practical Numerical Model for Wave Propagation and Fluid-Structure Interaction in Infinite Fluid

Safety assessment of existing pin-jointed grid structures with crooked members using static model updating

In pin-jointed grid structures, the commonly observed bending deformation of members affects the structural performance. The main aim of this study is to investigate the residual load-bearing capacity of an existing pin-jointed grid structure with crooked members, and a new model updating method using static measurement data is proposed to obtain a practical numerical model of the structure. First, the vertical displacements at multiple positions in the structure and the bending deformations of crooked members are selected as the static measurement parameters and measured. Then, the structure, including the crooked members, is adjusted from the load state at the moment of measurement to the zero-load state through global optimization. Finally, the updated finite element model with crooked members is utilized to assess the residual load-bearing capacity of the overall structure. In this study, a load experiment using a quadrangular pyramid grid structure with artificial crooked members is conducted, and the experimental results validate the proposed method.

Landslide Accumulation Ice-Snow Melting for Thermo-Hydromechanical Coupling and Numerical Simulation

In this paper, we discussed the phase change coupling algorithm of accumulation bank slope under the action of ice-snow melting. We described the effect of temperature gradient on the water migration of soil. We simplified the stress balance, continuity, and energy equation in the coupled model. We discussed the variation law of temperature, seepage, and stress (deformation) field under different conditions of ice-snow melting on the bank slope of the accumulation body. Based on the three-field coupling energy balance equation of ice-snow melting with phase change, the simplified algorithm of three-field coupling is obtained. The simplified algorithm is applied to the coupling model of ice-snow thawing on indoor accumulation bank slope. We established a practical numerical model for the coupling analysis of temperature, seepage, and stress field. We established the coupled control differential equation of three fields. We investigated the three-dimensional numerical simulation of stress, displacement, plastic deformation, and other indicators. The results show that the numerical simulation results are in good agreement with the monitoring results. It is expected that the research results can more truly simulate the actual characteristics of ice and snow melting water on the bank slope of the Three Gorges Reservoir and provide reference for the prevention and prediction of extreme snow and ice disasters in the Three Gorges Reservoir area.

Modeling spray combustion using multi-component surrogate fuels

Kerosene and diesel fuels involved in spray combustion operations are complex fuels composed of a wide and diverse variety of hydrocarbon components. For practical numerical modeling of the evaporation and combustion phenomena in a combustor, well-designed surrogates fuels that can mimic the real fuel thermal and chemical properties can be utilized. In this study, predictions and validations of the influence of fuel on the liquid and vapor penetration characteristics within a constant-volume chamber were first performed utilizing a benchmark m-xylene/ n-dodecane, Jet-A, and diesel surrogate fuels. Then, simulations of reacting spray of a bi-component m-xylene/ n-dodecane fule, and a four-component Jet-A surrogate fuel ( n-dodecane (C12H26), iso-cetane (C16H34), trans-decalin (C10H18) and toluene (C7H8)) were studied aided by skeleton chemical kinetic mechanisms available from the literature. The results of ignition delay time, lift-off length, radicals, and the mass fraction histories of fuel species were comprehensively used to assess the performance of relevant thermophysical and chemical sub-models. Two different chemical mechanisms were compared in detail to investigate the effect of the chemical kinetics model on the flame structures and spray characteristics. It has been found that the spray ignition of multi-component fuels is remarkably influenced by the chosen chemical kinetic mechanism and less affected by the droplet evaporation models.

A nonnegative and shape‐preserving global transport model on cubed sphere using high‐order conservative collocation scheme

AbstractA numerical model for global tracer transport is implemented by using Gauss–Legendre‐point conservative collocation (GLPCC) scheme on cubed sphere. Three‐point GLPCC scheme can achieve fifth‐order accuracy in the spherical geometry. To remove the spurious oscillations in the regions with strong gradients or discontinuities, the hierarchical reconstruction (HR) is applied to the “troubled cells” identified by a smoothness indicator based on the WENO concept. To assure the positivity‐preserving property, a flux correction operation is adopted to impose the restriction on the mass reduction due to the fluxes leaving the cell edges. The proposed numerical scheme aims to remove the nonphysical oscillations while preserving the accuracy in the smooth regions and maintain the compact spatial stencil as far as possible by making full use of degrees of freedom. The proposed schemes are evaluated by simulating the widely used benchmark tests for advection equation in one dimension and multidimensions of spherical geometry. Numerical results show that the fifth‐order accuracy is well preserved for smooth problems, while numerical oscillations can be effectively removed and the nonnegativity of the solutions is strictly guaranteed. It is very promising to develop the practical numerical model for tracer transport computation in atmospheric general circulation models using the proposed numerical framework.

Numerical modeling of post-flood water flow in pavement structures

Water infiltration through pavement structures as a result of flooding and/or extreme rainfalls, can adversely influence the bearing capacity of the pavement and lead to its premature failure. Since the entire pavement system will not be always in saturated state, the post-flood water movement throughout its granular layers should be formulated based on unsaturated flow principles. This study is aimed at developing a practical numerical model for simulating the partially saturated water flow in pavements caused by surface infiltration. To this end, available numerical methods and software packages are evaluated based on the relative merits of availability and computational rigor. The selected method is validated with published data. Existing correlations are used to reduce the number of inputs required for modeling. Subsequently, a parametric study is carried out to investigate the influence of material properties, such as aggregate gradation, and environmental conditions, such as rainfall intensity and duration, on the pavement’s response. Special cases, such as anisotropic material and clogged drainage are also modeled. This study provides an insight into the hydraulic behavior of pavement structures subjected to severe precipitation. In addition, this model establishes a solid basis for subsequent structural analyses to fully understand the behavior of inundated pavements under traffic loadings.

Magneto-thermal-convection stability in an inclined cylindrical annulus filled with a molten metal

PurposeMetal-cooled reactors generally use molten metals such as sodium, potassium or a combination of sodium and potassium because of their excellent heat transfer properties so that the reactor can operate at much lower pressures and higher temperatures. The purpose of this paper is to investigate the stability of natural convection in an inclined ring filled with molten potassium under the influence of a radial magnetism.Design/methodology/approachA numerical simulation of electrically conductive fluid natural convection stability is performed on an inclined cylindrical annulus under the influence of a radial magnetism. The upper and lower walls are adiabatic, while the internal and external cylinders are kept at even temperatures. The equations governing this fluid system are solved numerically using finite volume method. The SIMPLER algorithm is used for pressure-speed coupling in the momentum equation.FindingsNumerical results for various effective parameters that solve the problem in the initial oscillatory state are discussed in terms of isobars, isotherms and flow lines in the annulus for a wide range of Hartmann numbers (0 ≤ Ha ≤ 80), inclination angles (0 ≤ γ ≤ 90°) and radii ratios λ ≤ 6. The dependency stability diagrams between complicated situations with the critical value of the Rayleigh number RaCr and the corresponding frequency FrCr are established on the basis of the numeric data of this investigation. The angle of inclination and the radii ratio of the annulus have a significant effect on the stabilization of the magneto-convective flux and show that the best stabilization of the natural oscillatory convection is obtained by the intensity of the strongest magnetic field, the high radii ratio and inclination of the annulus at γ = 30°.Practical implicationsThis numerical model is selected for its various applications in technology and industry.Originality/valueTo the best of the authors’ knowledge, the influence of the inclination of the cylindrical annulus (ring), with various radii ratio, on natural oscillatory convection under a radial magnetism has never been investigated.