Technology foresight for the South African road transport sector by 2035

DATA AVAILABILITY : The authors confirm that the data supporting the findings of this study are available within the article.BACKGROUND : Foresight can be used to define futuristic orientated research and development (R&D) that is required to position the road transport sector for a challenging future. OBJECTIVES : To develop a set of futuristic R&D projects that could be added to a balanced SANRAL R&D portfolio to position SANRAL and the transport sector for the future on a 15-year horizon. METHOD : Inputs into and ranking of the drivers, trends and technologies that will impact the transport sector were obtained from interviews with eminent thinkers, participants in workshops and a survey leading to five potential future scenarios. Qualitative and quantitative data analysis yielded several key solutions (KSs) and key interventions (KIs) to position the sector. This was complemented with the novel use of technology trees to analyse the linkages between new and existing knowledge and to identify gaps in knowledge and subsequently the identification of key R&D opportunities. RESULTS : Through backcasting from the desired future scenario as well as using 412 stakeholder inputs, 12 KSs and 61 KIs were defined and ranked. The top 30, most futuristic KIs were analysed using 18 hierarchical technology trees to define R&D opportunities. CONCLUSION : The analysis emphasised the importance of new technologies such as data science, machine learning, smart transport and advanced materials to position the sector. CONTRIBUTION : The use of a novel, structured technology foresight approach that utilises scenario development combined with hierarchical technology trees was demonstrated. To position the road transport sector for a challenging future, 12 new thematic KSs and 61 KIs were developed.SANRAL SOC LTD.http://www.jtscm.co.zaam2024Civil EngineeringSDG-09: Industry, innovation and infrastructur

Two-relaxation-time Lattice Boltzmann scheme: About parametrization, velocity, pressure and mixed boundary conditions

We develop a two-relaxation-time (TRT) Lattice Boltzmann model for hydrodynamic equations with variable source terms based on equivalent equilibrium functions. A special parametrization of the free relaxation parameter is derived. It controls, in addition to the non-dimensional hydrodynamic numbers, any TRT macroscopic steady solution and governs the spatial discretization of transient flows. In this framework, the multi-reflection approach [16,18] is generalized and extended for Dirichlet velocity, pressure and mixed (pressure/tangential velocity) boundary conditions. We propose second and third-order accurate boundary schemes and adapt them for corners. The boundary schemes are analyzed for exactness of the parametrization, uniqueness of their steady solutions, support of staggered invariants and for the effective accuracy in case of time dependent boundary conditions and transient flow. When the boundary scheme obeys the parametrization properly, the derived permeability values become independent of the selected viscosity for any porous structure and can be computed efficiently. The linear interpolations [5,46] are improved with respect to this property.status: publishe

Study of simple hydrodynamic solutions with the two-relaxation-times lattice Boltzmann scheme

For simple hydrodynamic solutions, where the pressure and the velocity are polynomial functions of the coordinates, exact microscopic solutions are constructed for the two-relaxation-time (TRT) Lattice Boltzmann model with variable forcing and supported by exact boundary schemes. We show how simple numerical and analytical solutions can be interrelated for Dirichlet velocity, pressure and mixed (pressure/tangential velocity) multi-reflection (MR) type schemes. Special care is taken to adapt them for corners, to examine the uniqueness of the obtained steady solutions and staggered invariants, to validate their exact parametrization by the non-dimensional hydrodynamic and a "kinetic" (collision) number. We also present an inlet/outlet "constant mass flux" condition. We show, both analytically and numerically, that the kinetic boundary schemes may result in the appearance of Knudsen layers which are beyond the methodology of the Chapman-Enskog analysis. Time dependent Dirichlet boundary conditions are investigated for pulsatile flow driven by an oscillating pressure drop or forcing. Analytical approximations are constructed in order to extend the pulsatile solution for compressible regimes.status: publishe

Lattice Boltzmann method for double-diffusive natural convection

A lattice Boltzmann method for double-diffusive natural convection is presented. The model combines a multicomponent lattice Boltzmann scheme with a finite-difference solution of the energy equation to simulate natural convection caused by gradients in temperature and concentration. The model is validated both in two and three dimensions, and the agreement with literature data is satisfactory. A case study of thermosolutal convection of air in a cubical enclosure with horizontal thermal and solutal gradients is presented, exhibiting a rich variety of flow structures.status: publishe

1D combined flow and thermodynamic modelling of a lead blast furnace

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Dissolution of a solid sphere in a multicomponent liquid in a cubic enclosure

In this paper we present a numerical investigation of the dissolution process of a solid spherical particle in a cubical enclosure. The numerical setup is inspired by the experimental observation of the dissolution of Al2O3 particles in a CaO Al2O3-SiO2 containing liquid at elevated temperatures by confocal scanning laser microscopy. To gain insight into the dissolution behavior, a systematic numerical study has been undertaken of several parameters influencing the dissolution process. The presented results can directly be used to estimate the time to complete dissolution or the diffusion coefficient in a dissolution experiment.status: publishe

A thermodynamic model of the EAF process for stainless steel

A time-dependent thermochemical model has been developed for the electric arc furnace process for stainless steel production. The material input for the model was generated by reconciliation of industrial data. A reconciliation procedure has been used which allows correction of concentrations and total masses of the streams with linear constraints. The energy input is approximated from industrial data and scaled through an efficiency factor. Time dependency is implemented by a stepwise input of energy and matter into an equilibrium reactor. The equilibrium calculations are performed using data from FACT-databases and implemented using the programming library ChemApp. The model is used to calculate the evolution of temperature and composition of gas, slag and metal phases with time. Agreement of the end composition in the metal phase with industrial data is good. In the slag phase, however, Cr, Fe, Mn and Si are oxidized significantly less than expected due to an overestimation of CO-gas formation. The behaviour of the equilibrium model can provide some insight into the kinetics of the process.status: publishe

Interfacial reactions during the dissolution of titanium in liquid iron

The interfacial reactions between a solidified Fe shell and Ti were investigated within the framework of steel alloying. Ti cylinders were immersed into liquid Fe for various durations and subsequently water-quenched. An Fe shell solidifies around the Ti. At the interface between Fe and Ti a reaction zone is formed. Initially it consists of a liquid eutectic layer, though in later stages all stable phases at elevated temperature can be found in the quenched microstructure. The larger part of this reaction zone is fluid at high temperature and both Ti and Fe dissolve into it. Moreover, intermetallic compound formation and mixing of Fe and Ti generate extra heat, shortening the time required for shell melt-back. The reaction zone reaches thicknesses up to 40 % of the initial sample’s radius and when the shell has completely remolten, a discontinuity in the thickness-time profile is expected. The exact morphology of the reaction zone at high temperature remains to be determined: presence of a solid layer of Fe2Ti may impede mixing in the initial stages.status: publishe

Lattice Boltzmann model for diffusion-controlled indirect dissolution

Indirect dissolution is modelled using a two-component lattice Boltzmann model. A boundary condition is developed to impose equilibrium concentrations on the interfaces. The interfaces are captured using a volume-tracking scheme. The model is applied to a one-dimensional diffusion couple and the expected behaviour is observed. A two-dimensional situation with and without convection is also simulated, and the behaviour under grid refinement is studied. © 2007 Elsevier Ltd. All rights reserved.status: publishe

Observing nitrogen bubbles in liquid zinc in a vertical Hele-Shaw cell

Observations of gas bubbles in liquid metal are strongly hindered by the opacity of metals. To circumvent this limitation, the authors recently proposed to study such systems under quasi-2D flow conditions in a Hele-Shaw cell. The current paper presents a successful application of this approach for nitrogen bubbles in liquid zinc at 973 K (700 °C) in a fused quartz cell with a thickness of 1.5 mm. At low oxygen levels, the cell walls are not wetted by the liquid zinc, and bubbles can be observed directly through the transparent cell walls. Furthermore, using a moving high-speed camera that travels upwards with the bubbles, their properties are quantified in detail along the entire trajectory. In the range of equivalent diameters between 5.9 and 9.0 mm, this reveals a single periodic flow regime in which bubbles follow a sinusoidal path with a characteristic frequency of 3.31 Hz. In addition, systematic intermediate accelerations are observed of which the origin remains unexplained. Considering the unprecedented resolution of such observations for bubbles in liquid metals, especially at high temperatures, it is expected that this approach will contribute to a better understanding of the mechanisms that govern gas injection in pyrometallurgy.status: publishe