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Adaptive Time Step and Solver for Discrete Element Method - Beam Bond Model
Get PDFThis contribution introduces an adaptive strategy for time-stepping and solver
selection in simulations based on the Discrete Element Method with beam bond models (DEMBBM).
In this approach, particles are connected by virtual beams capable of transmitting axial,
shear, and bending forces, enabling the simulation of both discrete and continuum mechanical
behaviour. Such capabilities are particularly relevant in crack propagation problems, where an
initially continuous structure is progressively disrupted by fracture. While DEM is traditionally
solved using explicit or semi-implicit integration schemes, certain classes of DEM-BBM
problems, such as those involving progressive fracture, can benefit from implicit methods.
These allow for longer time steps without compromising numerical stability. However, the time
step size can affect the accuracy of the solution, particularly under rapidly changing conditions.
For this reason, it must be continuously adapted based on the current state of the system, with
respect to velocities, stress distribution, and oscillatory response. Depending on the state of the
system, different solver types can be employed. When the system remains stable and the time
step is constant, direct solvers offer high efficiency. In contrast, when frequent structural
changes occur, such as during fracture development, iterative solvers are more suitable. The
proposed strategy enables dynamic transitions between solver types and time-stepping
adaptions, which improves robustness and computational performance
Computational analysis of carbon-neutral biofuels co-firing in a rotary kiln
Get PDFThis study presents a computational fluid dynamics (CFD) analysis of biomass co-firing in an industrial rotary kiln as a pathway toward reducing fossil fuel dependency and supporting decarbonization strategies. A three-dimensional multiphase model was developed in ANSYS Fluent, where biomass was represented as multi-component particles undergoing sequential processes of drying, pyrolysis, and char oxidation. Two operating scenarios were evaluated: (i) a baseline case with natural gas as the sole fuel, and (ii) a co-firing case in which 10% of the thermal input was provided by carbon-neutral biofuels.
The results highlight the influence of biomass addition on the thermal field and particle behavior. While a slight reduction in peak flame temperature was observed after biomass injection, the overall temperature distribution and bed heating profiles remained stable and adequate for process requirements. Particle-scale analysis confirmed complete thermal conversion, with moisture release, volatile consumption, and char oxidation leading to full burnout within the residence time.
These findings demonstrate the technical feasibility of partial biomass substitution in rotary kilns and emphasize the value of CFD modeling as a predictive tool for evaluating combustion stability, particle conversion, and process efficiency in high-temperature industrial systems
Simulating interparticular forces in cementitious media using the Discrete Particle Method
Get PDFConcrete is by far the most produced material in the world, at around 15 billion tonnes
per year [1]. Given the scale of production and the associated use of cement, the concrete industry
is a large CO2 emitter, responsible for more than twice the CO2 emissions of global
aviation [2, 3]. Consequently, concrete offers significant potential for climate impact mitigation
by reducing the embodied CO2 per kilogram of material [4]. Concrete consists mainly of sand,
gravel, water, and Portland cement clinker, with the latter being the main source of its high
global warming potential. Therefore, the ongoing research effort is to minimise the amount of
clinker in concrete by pursuing two different strategies: the development of alternative binders
and the optimisation of concrete composition. This study follows the latter approach. Optimising
concrete composition requires a detailed understanding of the interparticular forces that
occur. These forces are complex, and an efficient yet accurate strategy is required to predict
and investigate their effects on small scales, with the aim of upscaling to concrete in the future.
Therefore, this study investigates the linear viscoelastic contact model with adhesion forces to
capture the interactions between cement clinker, limestone filler, and quartz sand in an alkaline
solution. The contact model is then used to simulate the packing problem with three distinct
materials. The resulting packing density is compared to the same simulation, without interparticular
forces
Comparative life cycle assesment (LCA) of a boat hatch made of glass fibre and flax fibre reinforced composites
No full textThe widespread use of glass fibre-reinforced composites in the marine industry is primarily attributed to their low cost, favourable mechanical properties, and high resistance to marine corrosion. However, their limited recyclability poses significant environmental concerns at end-of-life (EoL). Consequently, more sustainable alternatives such as biocomposites reinforced with natural fibres are being explored. This study presents a comparative Life Cycle Assessment (LCA) of the fore hatch of a small boat, currently manufactured by hand lay-up using glass fibre reinforced polyester glass fibre (GFRP), and a proposed alternative with flax fabric reinforced bio-epoxy (FFRB) produced by vacuum infusion. Initially, FFRB laminates were manufactured and mechanically characterised through three-point bending tests. Based on ISO 12215-5:2019 for small craft construction, the required laminate thicknesses for the FFRB hatch were determined, achieving a 14% weight reduction compared to the GFRP counterpart. Subsequently, a cradle-to-grave LCA was performed using OpenLCA software and the Ecoinvent v3.9.1 database. Results revealed that the FFRB hatch offers lower environmental impacts in fossil fuel depletion (ΔADP = –16%) and human toxicity (ΔHTP = –54%). However, terrestrial ecotoxicity (ΔTETP = +238%) increased due to pesticide and fertiliser use in flax cultivation. In conclusion, FFRB represents an environmentally sustainable alternative for marine component manufacturing, although further research is required to enhance its end-of-life performance
Eco-design in Automotive through 'Material Matrix Assessment': Use Case in the Salient Project
No full textEco-design in the automotive sector integrates environmental considerations into the product development process to minimize impact throughout the vehicle’s entire life cycle. This approach addresses aspects such as resource efficiency, emission reduction, and end-of-life options (recycling, reuse, etc.). In recent years, eco-design has gained relevance due to increasing regulations and growing user awareness of sustainability. However, its implementation is often based on Life Cycle Assessment (LCA), a complex and demanding method during early design phases, as it requires detailed data to deliver reliable comparative results. This can delay the development time of new components—a critical parameter in the automotive industry. To overcome this limitation, CTAG has developed its own methodology, the Material Matrix Assessment, which enables rapid preliminary analysis of multiple designs without requiring detailed specifications. This qualitative methodology can identify designs with the highest environmental potential using key metrics selected by a multidisciplinary team. Each category is scored and weighted according to its relevance, resulting in an overall score for each design concept. The Material Matrix Assessment was successfully applied in the European SALIENT project, using a front-end structure as a use case. In addition to facilitating the selection of the design with the lowest environmental footprint from the earliest stages of development, the methodology also enabled a system weight reduction of over 40%
A Comparative Analysis of the Boundary Condition Schemes for an Immersed Cylinder in a Water Stream with the Lattice Boltzmann Method
Get PDFIn this paper, we investigate the performance of different boundary condition (BC) schemes for curved walls within the framework of the Lattice Boltzmann Method (LBM). A canonical benchmark problem—the flow past a circular cylinder in a channel—is considered, with Reynolds numbers ranging from 50 to 300. While prior studies have examined similar configurations, this work provides a novel comparative analysis under realistic conditions—using dimensional LBM simulations with actual fluid properties and consumer-grade hardware, rather than idealized lattice units. Additionally, we introduce an in-house GPU-accelerated solver, enabling efficient high-fidelity simulations without reliance on specialized computational resources. Four wall boundary conditions—the standard bounce-back scheme, the non-equilibrium extrapolation scheme, the fictitious equilibrium scheme and a one-point scheme—are implemented and analyzed through their influence on the time-averaged drag coefficient of the cylinder. The results are compared against both experimental and Navier-Stokes-based numerical data to assess accuracy. Additionally, the study evaluates the relative impact of outlet BC selection on simulation fidelity. The findings show that all tested solid wall boundary schemes can produce reasonable predictions under suitable conditions. Furthermore, based on our results, the accuracy of LBM simulations is notably more sensitive to the choice of the outlet boundary condition when compared to the choice of the ones used at the immersed body.OPEN ACCESS Received: 08/05/2025 Accepted: 24/06/2025 Published: 27/10/202
Dynamic and Control in a Three-Variable Chemical Reaction Model
Get PDFChaotic behavior in nonlinear chemical systems presents significant challenges for stability and control, particularly in practical applications. This study investigates the suppression of chaos in a three-variable reaction system through an optimal linear feedback strategy, formulated via the solution of an algebraic Riccati equation. The proposed control approach effectively eliminates chaotic oscillations, guiding the system to equilibrium even under parameter uncertainties of up to 20%. Numerical simulations confirm that the control action maintains high robustness, ensuring convergence with minimal effort. The stabilization time for
Optimum Analysis and Parameter Inference of a New Improved Adaptive Progressive Unit-Weibull Model Censoring with Two Physical Applications
Get PDFRecently, a new bounded version of the Weibull lifetime has been introduced, retaining the flexibility of the standard Weibull model while restricting it to the unit interval, making it particularly useful for betalike modeling in various fields. This paper investigates the improved adaptive Type-II progressively censored plan by applying it to the bounded unit Weibull distribution. From a frequentist perspective, both maximum likelihood and maximum product of spacings methods are used, along with appropriate approximate confidence intervals. Bayesian point estimates, along with Bayesian credible intervals, are obtained using classical procedures that involve Markov-Chain Monte Carlo sampling, with two separate posterior distributions based on the squared error loss. The proposed estimation frameworks encompass both distribution parameters and key reliability metrics, notably the reliability and failure rate functions. Extensive simulations are conducted to evaluate the accuracy and efficiency of the estimators under various censoring levels, sample sizes, and thresholds. To determine the optimal removal strategy under both frequentist estimation paradigms, several metrics are proposed. Additionally, the model is applied to two real-world datasets from engineering reliability; one contains core samples from petroleum reservoirs collected across four cross-sections, and the other pertains to the tensile strength of polyester fibers, illustrating its practical utility and flexibility in modeling. The novelty of this study lies in integrating the bounded support of the unit-Weibull model with an improved adaptive censoring scheme, providing enhanced robustness and adaptability in reliability analysis across different fields.OPEN ACCESS Received: 21/06/2025 Accepted: 19/08/2025 Published: 27/10/202
Approximate Calculation of the Generalized Erdélyi-Kober Operator Using a Cubic Spline
Get PDFThis article investigates the problem of approximating the generalized Erdélyi-Kober fractional operator (often referred to as the Lowndes operator) using cubic splines. A method based on cubic spline interpolation is proposed for approximating the operator on a non-uniform grid. The convergence rate of the proposed method is proven, and its stability is analyzed. Error bounds are established for functions in the class C4[0; b], providing a mathematical justification for the accuracy of the approximation. The efficiency of the method is validated through practical examples using test functions such as f (x)= x4.7and f (x)= cos x, with results presented in graphical and numerical forms. This approach ensures high accuracy and flexibility in computing fractional integrals, which is of significant importance for solving fractional models used in physics, engineering, and other sciences. The article also provides an overview of the role of the generalized Erdélyi-Kober operator in modern fractional calculus and its applications.OPEN ACCESS Received: 06/06/2025 Accepted: 08/09/2025 Published: 27/10/202