Advanced Numerical Modeling Techniques Research Articles

3D electromagnetic assessment of bended CORC® cables

Conductor on round core (CORC®) cables have emerged as a leading contender in high-temperature superconducting (HTS) cable designs, offering exceptional performance with current densities surpassing 300 A/mm2 and the ability to withstand high axial tensile and compressive strain. Despite their remarkable properties, optimizing CORC® cables remains a challenge, particularly in accurately estimating their AC losses under real-world conditions, which necessitates advanced numerical modeling techniques. Building upon recent advancements in simulating straight CORC® cables, where Bean’s-like current profiles were observed across the actual thickness of wound superconducting tapes, we introduce a tailored computational approach to enhance the processing speed of three-dimensional (3D) finite element models of wound HTS tapes. This tailored approach is specifically designed to address the complexities of bent CORC® cables, which exhibit helicoidal winding and are subjected to varying mechanical strain. We focus on analyzing their electromagnetic performance by transitioning from idealized straight-former designs to more realistic scenarios where cable-formers are bent to accommodate flexible cable routing or coil configurations. Our simulations consider a typical cable design comprising three 4 mm-wide SuperPower tapes (SCS4050) with a twist pitch of 40 mm. We demonstrate the capability to accurately model the full electromagnetic behavior of bent CORC® cables without the reduction of degrees of freedom, providing valuable insights into their performance under bending conditions. Our findings contribute to the ongoing optimization of CORC® cable designs for a wide range of practical applications in high-current and high-magnetic field environments.

Constitutive and numerical modelling for timber-metal connections under large deformations

Computational modelling of complex timber-metal connections undergoing large deformations is crucial for the design of safe and robust multi-storey timber structures. Accurate simulation through large deformations requires constitutive models that suitably capture the full post-elastic behaviour of materials. Post-elastic behaviour of timber is particularly challenging to model due to strong anisotropy and material non-linearity in the post-elastic regime. Efficient simulation of complex connections requires advanced numerical modelling techniques to expedite explicit solution in the finite element domain. In this study, a suitable constitutive model for ductile metal components through large deformations, including consideration of stress localisation and triaxiality post-necking, is described. Some existing constitutive models for timber are discussed, and new constitutive models capturing both ductile and brittle failure modes are presented. A new formulation of the Hoffmann yield criterion with isotropic hardening for explicit solution is presented, and new VUMAT user subroutines for explicit solution in ABAQUS for Hoffmann, Sandhaas, Gharib, Hill-Gharib and Hoffmann-Gharib models are developed and made available for the benefit of other researchers. A benchmarked numerical model incorporating advanced modelling techniques to improve computational efficiency without compromising accuracy is presented for a complex timber, aluminium and steel dowelled beam-column connection tested shear and moment dominated testing. The simulation results compare favourably with experimental results in the literature, demonstrating that the proposed constitutive models and numerical modelling techniques provide realistic predictions of behaviour, including failure mode, and thus have the potential to support the design of complex timber-metal connections through large deformations under quasi-static and dynamic loading.

Assessing heat risk in a sub-saharan African humid city, Lagos, Nigeria, using numerical modelling and open-source geospatial socio-demographic datasets

In Sub-Saharan Africa, many cities are facing an increased risk of heat due to climate change and rapid urbanization. This poses a particular threat in areas with limited adaptive capacity. However, there is a lack of comprehensive heat risk assessment in the region, possibly due to the absence of high-resolution weather data. This study aims to address this gap by proposing and demonstrating a methodology for mapping high-risk areas in a tropical humid city, specifically focusing on Lagos, Nigeria. The approach utilises advanced numerical modelling techniques and open-source geospatial data.The urbanised Weather Research and Forecasting (WRF) model is employed to simulate Humidex-based heat stress during a specific heatwave event in March 2020. Open-source high resolution geospatial datasets were used to assess heat exposure and vulnerability. The urban areas were classified based on the Local Climate Zone (LCZ) scheme. Spatial analysis techniques, including Moran’s I test and Optimized Hot Spot Analysis (OHSA), were used to identify spatial clustering patterns and hot spots of heat risk areas.Moreover, using Gi* statistics in OHSA, the risk layer was categorised into hot, cold, and non-significant spots at various levels of significance (90 %, 95 %, and 99 %). Mapping the hot spots at the highest confidence level of 99 % identified Critical Heat Risk Zones (CHRZ), covering an area of approximately 423 km2. The results showed significant heat risk in highly urbanised LCZs. Further investigation indicated that the largest proportion of high-risk zones corresponded to densely populated and highly urbanised LCZs- LCZ3 (59 %), LCZ 6(21 %), and LCZ 7(17 %). Notably, these areas coincide with two well-known slums in Lagos, emphasizing the need for targeted interventions and planning measures in these areas.The findings highlight the magnitude and extent of heat risk within the city and emphasize the urgent need for targeted climate change adaptation and mitigation strategies in the identified high-risk zones.

MPACT OF WEATHER CONDITIONS ON FLIGHTS AND AIRCRAFT

Examine the effects of three phases of flight—takeoff and climb, enroute, descent, and landing and five different forms of unfavorable weather—fog, wind shear, thunderstorm, icing, and snow on aircraft operations and accidents. Methods: collect statistically up-to-date data and compare the data to estimate the impact of the various meteorological conditions on flights and the dangers of flight incidents. Use EJM to establish expert systems to report the impact of various weather conditions on flights. Results: evaluate the impact of weather events on flights and the necessity of prevention systems. Discussion: define the need of advanced numerical modeling techniques of time in Air Traffic Management systems.

Investigation on Behavior of Stone Columns in Soils under Predominant Settlement

Abstract: Recent advances have made stone columns more efficient and effective for addressing soil instability and improving the load-bearing capacity of weak soils. The present study aims to show that the behavior of stone columns can support most of the load transferred to the soil. The use of innovative materials, such as recycled glass, plastic, or tire shreds, as a replacement for traditional stone fill, has been investigated in recent years and has shown promising results in cost and sustainability. The development of advanced numerical modeling techniques, such as finite element analysis, has enabled engineers to understand the behavior of stone columns better and optimize their design for specific soil conditions. The load-displacement characteristics are considered governing parameters for understanding the capacity of stone columns. The study reveals that, stone column method significantly increases strength with the use of concrete waste lo demolished waste rather than stone aggregate, which can overcome this soil behavior. Additionally, stone columns are helpful for soil stabilization in areas with high water tables when other stabilization techniques are ineffective

Lattice Boltzmann Method in Modeling Biofilm Formation, Growth and Detachment

Biofilms are a complex and heterogeneous aggregation of multiple populations of microorganisms linked together by their excretion of extracellular polymer substances (EPS). Biofilms can cause many serious problems, such as chronic infections, food contamination and equipment corrosion, although they can be useful for constructive purposes, such as in wastewater treatment, heavy metal removal from hazardous waste sites, biofuel production, power generation through microbial fuel cells and microbially enhanced oil recovery; however, biofilm formation and growth are complex due to interactions among physicochemical and biological processes under operational and environmental conditions. Advanced numerical modeling techniques using the lattice Boltzmann method (LBM) are enabling the prediction of biofilm formation and growth and microbial community structures. This study is the first attempt to perform a general review on major contributions to LBM-based biofilm models, ranging from pioneering efforts to more recent progress. We present our understanding of the modeling of biofilm formation, growth and detachment using LBM-based models and present the fundamental aspects of various LBM-based biofilm models. We describe how the LBM couples with cellular automata (CA) and individual-based model (IbM) approaches and discuss their applications in assessing the spatiotemporal distribution of biofilms and their associated parameters and evaluating bioconversion efficiency. Finally, we discuss the main features and drawbacks of LBM-based biofilm models from ecological and biotechnological perspectives and identify current knowledge gaps and future research priorities.

A methodology for fragility analysis of buried water pipes considering coupled horizontal and vertical ground motions

Abstract With recent advances in computational capabilities as well as broad improvements in ground motion characterization and inelastic modeling of structural and geotechnical systems, large-scale direct models for underground structures—e.g., tunnels, water reservoirs, etc.—can now be devised with relative ease and deployed in engineering practice. In this study, a fragility-based seismic performance characterization for pipes is presented and demonstrated on two steel water pipes. Existing guideline documents and design codes are used for defining the performance criteria; and the fragility functions are developed through a Probabilistic Seismic Demand Analysis procedure for a variety of ground motion intensity measures. 800 nonlinear time-history analyses are carried out for computing the fragility functions. The analyses featured advanced numerical modeling techniques developed for soil-structure interaction problems, which included the Domain Reduction Method for injecting free-field motions into a truncated simulation domain, and the Perfectly Matched Layers for absorbing the scattered waves. The analyses are carried out using nonlinear models for both soil layers and the pipe, and coupled horizontal and vertical input ground motions. Finally, fragility surfaces of two steel water pipes, which consider the intensity measures in both horizontal and vertical directions, are devised for various soil layer profiles and engineering demand parameters.

Modeling large non-axisymmetric aerodynamic forces on a space launcher’s afterbody

A new article employs advanced numerical modeling techniques to investigate the large scale dynamics of a high Reynolds number axisymmetric separating/reattaching flow.

Investigation on seismic behavior of bridge piers with thin-walled rectangular hollow section using quasi-static cyclic tests

This study aims to investigate the seismic behavior of thin-walled rectangular hollow reinforced concrete (RC) bridge piers through quasi-static cyclic tests. For this purpose, two identical 1:12 scale specimens were designed and tested under different loading protocols. One specimen was subjected to displacement-controlled cyclic lateral loading with a constant axial load, and the other to the same lateral loading history, but with a variable axial load. The behavior of both specimens was evaluated in terms of the damage progression and failure mode, concrete crack width, hysteretic response, backbone curve, and residual displacement. The results revealed that both specimens experienced a mixed flexure-shear damage progression from the first crack through collapse. Flexural cracks were first observed in the flange surfaces, followed by the development of shear diagonal cracks in both web surfaces. Meanwhile, both specimens exhibited stable hysteretic behavior. Then, concrete spalling and longitudinal bar buckling were concentrated at the corners of the flanges due to the shear lag effect. Eventually, both specimens collapsed as a result of the flange local compression buckling. In addition, the specimen under a variable axial load collapsed much severer than the one under a constant axial load. Ultimate drifts of the specimens under a constant or variable axial load were 2.25% and 2%, respectively. This experiment provides valuable dataset for validating advanced numerical modeling techniques for thin-walled rectangular hollow RC piers, especially the data points in the collapse stage.

Scour at Bridge Foundations in Supercritical Flows: An Analysis of Knowledge Gaps

The scour at bridge foundations caused by supercritical flows is reviewed and knowledge gaps are analyzed focusing on the flow and scour patterns, available measuring techniques for the laboratory and field, and physical and advanced numerical modeling techniques. Evidence suggests that the scour depth caused by supercritical flows is much smaller than expected, by an order of magnitude compared to that found in subcritical flows, although the reasons for this behavior remain still unclear. Important questions on the interaction of the horseshoe vortex with the detached hydraulic-jump and the wall-jet flow observed in supercritical flows arise, e.g., does the interaction between the flow structures enhance or debilitate the bed shear stresses caused by the horseshoe vortex? What is the effect of the Froude number of the incoming flow on the flow structures around the foundation and on the scour process? Recommendations are provided to develop and adapt research methods used in the subcritical flow regime for the study of more challenging supercritical flow cases.

High Quality Steel Casting by Using Advanced Mathematical Methods

The main concept of this paper is to utilize advanced numerical modelling techniques with self-regulation algorithm in order to reach optimal casting conditions for real-time casting control. Fully 3-D macro-solidification model for the continuous casting (CC) process and an original fuzzy logic regulator are combined. The fuzzy logic (FL) regulator reacts on signals from two data inputs, the temperature field and the historical steel quality database. FL adjust the cooling intensity as a function of casting speed and pouring temperature. This approach was originally designed for the special high-quality high-additive steel grades such as higher strength grades, steel for acidic environments, steel for the offshore technology and so forth. However, mentioned approach can be also used for any arbitrary low-carbon steel grades. The usability and results of this approach are demonstrated for steel grade S355, were the real historical data from quality database contains approximately 2000 heats. The presented original solution together with the large steel quality databases can be used as an independent CC prediction control system.

3-D hydrodynamic modelling of flood impacts on a building and indoor flooding processes

Abstract. Given the current challenges in flood risk management and vulnerability assessment of buildings exposed to flood hazards, this study presents three-dimensional numerical modelling of torrential floods and its interaction with buildings. By means of a case study application, the FLOW-3D software is applied to the lower reach of the Rio Vallarsa torrent in the village of Laives (Italy). A single-family house on the flood plain is therefore considered in detail. It is exposed to a 300-year flood hydrograph. Different building representation scenarios, including an entire impervious building envelope and the assumption of fully permeable doors, light shafts and windows, are analysed. The modelling results give insight into the flooding process of the building's interior, the impacting hydrodynamic forces on the exterior and interior walls, and further, they quantify the impact of the flooding of a building on the flow field on the surrounding flood plain. The presented study contributes to the development of a comprehensive physics-based vulnerability assessment framework. For pure water floods, this study presents the possibilities and limits of advanced numerical modelling techniques within flood risk management and, thereby, the planning of local structural protection measures.

Suitability of the electromagnetic ring expansion test to characterize materials under high strain rate deformation

Characterisation of materials under high strain rate is always challenging, and requires sophisticated apparatus. Magnetic pulse forming techniques can involve high strain rate deformation and the electromagnetic ring expansion test (ERET) is considered here to determine its suitability to characterise materials at high strain rate. The multi-physics and high speed nature of the process requires advanced numerical modelling techniques to gain insight and understanding of stress development when used as a material characterisation technique. In order to evaluate the suitability of the ERET to fully characterise the material behaviour at high strain rate, stress states were investigated using 3D coupled mechanical-electromagnetic simulations on a validated numerical model. The numerical simulations were performed in LS-Dyna ® with a modified Johnson-Cook (MJC) material model in this study. Albeit the preliminary results show the development of biaxial stress during the test, a shielding mechanism is proposed to eliminate the axial component of the stress on the rings. This study indicates that the ERET has a potential to be used for characterisation of the material parameters under the influence of high strain rate.

Holocene shelf-coastal sedimentary systems associated with the Changjiang River: An overview

The fate of the terrestrial sediment supplied by rivers is a critical issue for understanding the patterns of Holocene environmental change on continental shelves. The East China Sea is a typical broad continental shelf with abundant sediment supply from large rivers. Here, a variety of sedimentary records were formed during the Holocene period. The sedimentary systems associated with these records have unique characteristics in terms of spatial distribution, material composition, deposition rate and the timing of deposition, which are related to active sediment transport processes induced by tides and waves, shelf circulations and sediment gravity flows. The sedimentary records thus formed are high resolution slices, i.e., each record has a temporal resolution of up to 100–10–1 a, but only covers a limited part of the Holocene time. In terms of the spatial distribution, these records are scattered over a large area on the shelf. Further studies of these systems are required to understand the underlying process-product relationships. In particular, the midHolocene coastal deposits on the Jiangsu coast, the early to middle Holocene sequences of the Hangzhou Bay, as well as the Holocene mud deposits off the Zhejiang-Fujian coasts, should be investigated in terms of the material supply (from both seabed reworking during the sea level rise event and river discharges), transport-accumulation processes, the sediment sequences and the future evolution of the sedimentary systems. Advanced numerical modeling techniques should be developed to meet the needs of these studies.

A Simplified Model for Predicting the Pollution Exchange Coefficient of Small Tidal Embayments

In recent years there has been a significant increase in the development and application of ever more sophisticated multi-dimensional models for solving the hydrodynamic and constituent transport equations which govern the flushing of pollution. However, advanced numerical modelling techniques can sometimes be augmented by alternative mathematical approaches which use simplified analytical solutions to predict the dispersion of contaminants. In the present article, a novel analytical tidal prism model is described for predicting the pollution flushing characteristics of small tidal embayments. The model relates the water quality response of the basin to the external forcing effects of the tide, the initial pollutant loading and the freshwater inflow rate. In general, the pollution flushing not only depends upon the geometry of the embayment and the tidal range but also on the proportion of effluent water which leaves the basin on an ebb tide, mixes with the surrounding coastal water and returns on subsequent flood tides. This effect has been taken into account in the mathematical model by the inclusion of a ‘pollution-return’ parameter. The analytical approach offers a viable and computationally inexpensive alternative to conventional multi-dimensional pollutant transport simulations and, more importantly, provides an increased understanding of the flushing characteristics of semi-enclosed tidal basins. The efficiency of the tidal flushing can be expressed in terms of the pollution exchange coefficient which measures the proportion of water exchanged with the sea each tidal cycle. To demonstrate the accuracy of the proposed mathematical formulation, analytical water quality predictions are compared against experimental pollution data from a 1:400 scale laboratory model of a generic square harbour. The results demonstrate that the analytical approach provides a simple and robust method of determining the water quality response of well-mixed tidal embayments.

Geotechnical aspects of rock tunnelling in China

To meet the huge demands of transportation, energy and other infrastructure projects, a large volume of rock tunnelling is being carried out across the country as China embarks on her modernization plan. This paper summaries the geotechnical issues encountered on such projects, including the various modes of rock mass instability and geological hazards. Methods of evaluating rock mass quality and ground conditions as developed in the West are now widely used on tunnelling projects in China. As well Chinese engineers and researchers have also developed geomechanical systems for rock mass classification, failure modes and support requirements. These systems have been proven to be effective in dealing with the complex geologic and tunnelling conditions in China. Also described in the paper are analytical techniques currently used in China for tunnel performance prediction, including canonical analysis, expert systems, block vector analysis and advanced numerical modelling techniques.