Combined Simulation Approach Research Articles

Investigations of the Cold Box Core Curing Stage Using an Augmented Simulation Approach

AbstractFoundry sand cores are used to produce complex metal castings. They are manufactured on universal coremaking machines in two distinct stages, shooting and curing. Various simulation tools exist to optimize the coremaking process. Numerical modeling of the two distinct process stages is challenging as it involves different tooling, raw materials, and process parameters. Additionally, each stage requires appropriate mathematical modeling of the fluid flow since the relevant physical phenomena are different. The state-of-the-art combined simulation approach (CA) can simulate these two stages in sequence using a Core shooting & curing module. The gassing system (GS) is also important to consider when calculating the complete physical mass flow during the curing stage in CA. An augmented simulation approach (AA) is proposed, which can include GS in the coremaking simulations. This approach enables the execution of two-stage combined simulations (CA) using Magma C + M software (SW1) and incorporates GS data using FLOW-3D CAST software (SW2). In order to analyze the influence of including selected factors such as the hopper during the shooting stage and GS during the curing stage, the simulation approaches CA and AA were compared. The simulation results were correlated with experiment results (EX) to analyze sand density distribution and different curing times, focusing on the final core quality. Quantity analysis has been done among EX samples to observe the cured core trend. The results obtained from AA exhibit a significantly better correlation with EX than with CA. The proposed augmented approach offers significant potential for the improved analysis, optimization, and accurate prediction of complex coremaking processes within polyurethane (PU) Cold Box Systems.

Drying and calendering of Lithium Ion battery electrodes: A combined simulation approach

In drying of battery electrodes, high drying speeds are desirable but lead to binder segregation resulting in lower adhesion strength and poorer electrochemical performance. During calendering, the elastic recovery of the electrode makes it difficult to estimate the line load required to achieve the desired porosity. The approach we present incorporates various drying and binder migration models and combines them with a calendering model as Sangros used it. The drying models taken from literature put a special focus on drying kinetics, binder segregation and particle dynamics. This information is passed to a solid-state bridge-based Discrete Element Method, which is additionally extended to include the interactions between the coating and the current collector. Through the interaction of these models, the mechanical behavior by means of stress and elastic recovery of model cathodes can be predicted for different degrees of compaction as well as areal loadings.

Explicit model predictive control of magnetorheological suspension for all-terrain vehicles with road preview

The integration of magnetorheological (MR) semi-active suspension systems in all-terrain vehicles (ATV) has garnered significant attention due to their ability to enhance damping performance and off-road capabilities. However, traditional control strategies result in poor control accuracy and limited vibration reduction effects when facing complex road excitations and impact disturbances. With technological advancements, enhanced vehicle environmental perception and road sensing capabilities have made it possible to implement model predictive control (MPC) for vehicle suspensions. Nevertheless, traditional MPC is limited in vehicle suspension applications due to its high computational complexity. To address these issues, this study introduces an explicit model predictive control based on road preview (EMPC-P). Firstly, road data obtained through a non-contact measurement method enables the system to perceive road excitation information in advance. Subsequently, a 7 Degree-of-Freedom (7-DOF) suspension model incorporating road excitations is constructed. By adhering to system constraints and employing a multiparameter optimization method, the control problem based on rolling optimization is transformed into an explicit polyhedral system. The offline precomputation of control state relations enhances the computational efficiency of the control system. Through this approach, the designed EMPC allows the vehicle suspension system to make optimal control decisions quickly and accurately in response to complex driving conditions, thus improving the damping effect of the system. Through a combined approach of simulation and experimental validation, the designed EMPC-P controller is compared with the Skyhook controller under preview and non-preview states, respectively. Empirical testing confirms that the EMPC-P exhibits superior damping effects, significantly improving vehicle ride comfort and handling stability.

Exergo-ecological analysis and life cycle assessment of agro-wastes using a combined simulation approach based on Cape-Open to Cape-Open (COCO) and SimaPro free-software

Thermochemical processes to convert bio-wastes into valuable products and bioenergy have been extensively studied in the literature. Experimental and, to a lesser extent, rigorous simulation papers concerning these processes have been widely considered and discussed in the literature. Nonetheless, there is still a gap to fill in providing a fast and reliable simulation scheme. In this paper, an efficient simulation strategy, combining the free-software COCO simulator for the bio-waste slow pyrolysis coupled with commercial SimaPro code to carry out the Life Cycle Assessment (LCA), was applied. The pyrolysis product yields at 673, 773, and 873 K were well predicted using mass and energy balances and a proposed reaction scheme from the literature. Simulations were validated using experimental data previously reported. The highest yield was 53.7% for biochar (673 K – stalk of white grape), 32% for bio-oil (773 K - marc of red grape), and 56.3% for gas (873 K - marc of white grape). The results from LCA and cumulative exergy demand (CExD) were useful to detect and reduce environmental impacts in previous stages of the process.

A new simulation approach for crack initiation, propagation and arrest in hollow cylinders under thermal shock based on XFEM

The core region of the reactor pressure vessel (RPV) can be considered as a hollow cylinder disregarding the geometrical details such as the nozzles. Under this consideration, a cylindrical mock-up with an axial crack can be used to investigate the behavior of initial defects under thermal shock (TS). In order to assess the crack initiation, propagation and arrest of an initial defect and to design mock-ups for TS experiments, a combined simulation approach of the Initiation-Growth-Arrest (IGA) algorithm and XFEM is proposed. The mock-up is designed taking into account the propagation of the initial defect and its arrest as well as several experimental criteria such as weight, size of the specimen, experimental feasibility, etc. The simulation strategy uses the stress intensity factors at every time increment of the TS event to estimate the possible crack propagation and brittle failure of the cylinder. The criterion for initiation of the crack propagation uses the temperature-dependent fracture toughness (KIc) of the material described by ASME fracture toughness model. For the crack arrest, the simulation approach uses the crack arrest fracture toughness of the material.After introducing the IGA algorithm and its implementation for XFEM, a 3D finite element model of a cylinder and material properties corresponding to an embrittled steel are introduced. Then, the IGA algorithm is combined with a closed-weight function formula (WFF) for axial crack in hollow cylinders, which is used as reference solution. The XFEM-initiation-growth-arrest (XFEM-IGA) and closed-weight function-initiation-growth-arrest (WFF-IGA) methods are applied on cylinders with different geometries to select the geometry of the mock-up designed for a thermal shock experiment. The results show that the crack stops for thick cylinders after several initiation-arrest cycles and that a reduction of the thickness provokes propagation of the crack until through-wall-crack happens. Beside the performance and application to an axial edged crack in a hollow cylinder, some limitations of the presented model are also discussed.

Improving the operations of an emergency department (ED) using a combined approach of simulation and analytical hierarchical process (AHP)

ABSTRACT This paper presents the results concerning the evaluation of the processes of an Emergency Department (ED). Based on the analysis of both processes and data flow, a simulation model of patient throughput in the ED has been developed. Simulation results, obtained using the JaamSim software, pointed out the strengths and weaknesses of the departments’ operations. Then, several alternative scenarios (hypothetical solutions) were created and tested, while the results were thoroughly analysed. In order to prioritise the several scenarios, two hierarchical processes were used. Firstly, a multicriteria table was developed based on decision makers’ personal preference. Total length of stay was acknowledged as the factor with the higher importance. Consequently, the application of an analytical hierarchical process (AHP) managed to verify the primary ranking. A comparison of the proposed ideas was attempted, featuring the implementation of a fast track unit as the best practice.

A Combined Simulation Approach to Evaluate Overtaking Behaviour on Two-Lane Two-Way Rural Roads

A significant percentage of road fatalities and injuries occur in the nonmotorway rural road network. One of the main causes of accidents on these roads is represented by overtaking, as, by its nature, it involves a risk of a head-on collision with oncoming traffic. The paper describes a combined simulation approach (driving simulator and traffic microsimulation) designed to examine the influence of different traffic conditions on passing manoeuvres on two-lane two-way rural roads. The main focus was the evaluation of the end of the passing manoeuvre because it reflects the risk of a head-on collision. In addition, the study aimed to assess the usefulness of the proposed combined approach in the ability to proactively and quickly diagnose traffic safety problems and consequently to evaluate appropriate solutions. The data collected with an interactive driving simulator on a sample of 54 participants have been used to adjust some input data of the traffic microsimulation software. A specific situation consisting of a stationary heavy vehicle obstructing the entire lane was repeated in both experiments. The analyses focused on time-to-collision (TTC), defined as the remaining gap between the passing vehicle and the oncoming vehicle at the end of the passing manoeuvre. The results showed that the type of manoeuvre performed is significantly influenced by the traffic condition. Furthermore, the manoeuvre is influenced by the gap between two successive vehicles in the opposite lanes. Focusing on the end of the manoeuvre, it was found how a traffic increase leads to a significant reduction of the TTC values. Furthermore, the comparative analysis conducted between the data recorded following the combined approach and those obtained using exclusively the input data of the microsimulation software supports the usefulness of the proposed methodology for conducting road safety analyses, especially in complex traffic environments where drivers’ behaviour plays a decisive role.

Determining the source and eruption dynamics of a stealth CME using NLFFF modelling and MHD simulations

Context. Coronal mass ejections (CMEs) that exhibit weak or no eruption signatures in the low corona, known as stealth CMEs, are problematic as upon arrival at Earth they can lead to geomagnetic disturbances that were not predicted by space weather forecasters. Aims. We investigate the origin and eruption of a stealth event that occurred on 2015 January 3 that was responsible for a strong geomagnetic storm upon its arrival at Earth. Methods. To simulate the coronal magnetic field and plasma parameters of the eruption we use a coupled approach. This approach combines an evolutionary nonlinear force-free field model of the global corona with a MHD simulation. Results. The combined simulation approach accurately reproduces the stealth event and suggests that sympathetic eruptions occur. In the combined simulation we found that three flux ropes form and then erupt. The first two flux ropes, which are connected to a large AR complex behind the east limb, erupt first producing two near-simultaneous CMEs. These CMEs are closely followed by a third, weaker flux rope eruption in the simulation that originated between the periphery of AR 12252 and the southern polar coronal hole. The third eruption coincides with a faint coronal dimming, which appears in the SDO/AIA 211 Å observations, that is attributed as the source responsible for the stealth event and later the geomagnetic disturbance at 1 AU. The incorrect interpretation of the stealth event being linked to the occurrence of a single partial halo CME observed by LASCO/C2 is mainly due to the lack of STEREO observations being available at the time of the CMEs. The simulation also shows that the LASCO CME is not a single event but rather two near-simultaneous CMEs. Conclusions. These results show the significance of the coupled data-driven simulation approach in interpreting the eruption and that an operational L5 mission is crucial for space weather forecasting.

Evaluating the role of commercial parking bays for urban stakeholders on last-mile deliveries – A consideration of various sustainability aspects

In this contribution, we assess the traditional last mile delivery concept and a framework with commercial parking bays for carriers in terms of their sustainability value for urban stakeholders. We evaluate the potential advantages and disadvantages of commercial parking bays and provide routing solutions based on the given context and stakeholder objectives. To ensure the needs of the stakeholders and the possibility of a near future implementation in the dynamic real-world system, we chose a combined approach of simulation and mathematical optimization, which allows us to investigate the concept efficiently and with a high reliability. By means of an agent-based simulation model as well as a mixed-integer linear model, we establish a heuristic routing solution for minimizing both emissions and delivery durations. We consider different scenarios in which customers are visited in a delivery radius, around a specific commercial parking bay. Outside this radius, delivery operations are conducted through second-row parking activities. Our results for the area of investigation show that the investigated scenario featuring a 200-m delivery radius around the parking bays has a 29.8% emission savings potential compared to traditional parcel delivery procedures. Moreover, optimizing the delivery routes with our green vehicle routing approach has indicated an additional savings potential of 26.4% in terms of delivery duration and 16.4% in terms of emission output for traditional parcel deliveries. Concerning the individual evaluation of the logistics context, our results indicate that dedicated commercial parking bays could be attractive to most urban stakeholders when employed utilizing a hybrid approach, combining traditional delivery activities with commercial parking bay fulfillment.

Hygrothermal Performance of Old Lime Plastered Spaces in a Hot and Dry Climate

Lime plaster is one of the key sustainable building materials which is also effective as a passive cooling strategy. Since it is being used for ages now, it is the most compatible material for old heritage structures. Thus, majorly used in conservation projects. In this work, the hygrothermal performance of lime plaster is observed through simulations and surveys. Residential surveys are carried out for occupied old naturally ventilated spaces. The inner surface temperature, relative humidity, and moisture content of the walls are measured. Simultaneously, the indoor air temperature, relative humidity, globe temperature, and air velocity are measured. In hygroscopic materials like lime plaster, realistic conditions like mold growth cannot be predicted through simulations. A simulation of thermal and hygrometric behavior of historical buildings is a challenge. An inaccurate simulation may lead to inadequate conclusions, which could lead to inappropriate and dangerous actions for the building’s heritage conservation. An attempt is made to use the survey readings and observations to predict the phenomenon of mold growth in a space while conducting simulations. Using a combined approach of simulation and survey, it was possible to predict the mold risk of the space.

Sound insulation of complex façades: A complete study combining different numerical approaches

Curtain walls present critical aspects related to noise insulation. Laboratory and field tests are traditionally the most used procedure to determine sound transmission loss. Even if they provide the best results, they are very expensive, time-consuming (at least two days) and the results are specific of the tested specimen and therefore they cannot be generalized. Conversely, traditional numerical used simulations are generally conducted through Statistical Energy Analysis (SEA) studies or analytical analysis. Both approaches do not offer reliable results as they need several laboratory tests and dedicated mathematical models.Thus, the aim of this research is to compute the curtain wall sound insulation by means of a combined simulation approach, using TMM and 3D acoustic model. The calibration and validation of this procedure is discussed in comparison with laboratory tests. Poroelastic materials as well as rigid metal stud are carefully characterized and sound source and sound field within both measured and simulated environment are calibrated and validated. Measurements are then compared with simulated transmission loss and a parametric study for mullions structure and their components is reported.Results clearly show how it is possible to completely simulate a laboratory test combining 3D simulation and Transfer Matrix Method results and how the influence of mullion components is of paramount importance for the final acoustical performances.

Simulation pathway for estimating heat island influence on urban/suburban building space-conditioning loads and response to facade material changes

Environmental thermal loading on urban buildings is expected to increase owing to the combined influence of a warming climate, increasing frequency and severity of extreme heat events, and the urban heat island (UHI) effect. This paper presents how a computationally efficient estimation pathway could be utilised to understand UHI influence on building energy simulations. As an example, this is examined by considering UHI influence on the space-conditioning loads of office buildings within urban and suburban conditions, and how the trend of replacing heavyweight facades with lightweight alternatives could affect their surrounding microclimates, as well as building energy use. The paper addresses this through simulations of street canyons based on the urban Moorgate and suburban Wimbledon areas of London. Results show that with all scenarios including the UHI within a dynamic thermal simulation presents between 2.5 and 9.6% net increase in annual space-conditioning. The study also demonstrates that the trend in urban centres to replace heavyweight facades with lightweight insulated alternatives increases space-conditioning loads, which in turn increases UHI intensity to create a warming feedback loop. The study therefore stresses the significance of including microclimate loading from the UHI in estimating urban and suburban energy use, and the combined simulation approach is presented as a computationally efficient pathway for use by built environment designers.

Numerical simulation and validation of material loadings during electrical discharge machining

The material removal mechanism of electrical discharge machining of steel bases on melting and evaporation of material by a spark discharge between two electrodes. Consequently, the electrode materials are stressed by an intensive thermal load that leads to changes of microstructure in the rim zones. For modelling these loads, a combined simulation approach of modeling heat transfer and fluid dynamics was implemented. Aim of this research is to develop a heat transfer model, which can reproduce the material removal and predict the local thermal load in the electrodes for correlation with the modifications in electrodes rim zones.

Uranyl-Glutardiamidoxime Binding from First-Principles Molecular Dynamics, Classical Molecular Dynamics, and Free-Energy Simulations.

Exploring the structural interplay of ligands with uranyl can provide important knowledge for technology advances in uranium extraction from seawater. However, obtaining such chemical information is not an easy endeavor experimentally. From a plethora of computational methods, this work provides both microscopic insights and free-energy profiles of the binding between uranyl and deprotonated glutardiamidoxime (H2B) for which experimental structural information is not available, despite H2B being an important model ligand with an open-chain conformation for understanding aqueous uranium extraction chemistry. In our molecular dynamics (MD) simulations, we explicitly accounted for the water solvent as well as the Na+ and Cl- ions. We found that hydrogen bonding plays a critical role in dictating the binding configurations of B2- and HB- with uranyl. Simulated free energies of sequential ligand binding to form UO2B, [UO2B2]2-, and [UO2(HB)B]- show very good agreement with the experimental values, lending support to our structural insights. The potential of mean force simulations showed the common feature of an important intermediate state where one end of the ligand binds to uranyl while the other end is solvated in water. Bringing the loose end of the ligand to bind with uranyl has a free-energy barrier of 15-25 kJ/mol. The present work shows that the combined simulation approach can reveal key structural and thermodynamic insights toward a better understanding of aqueous complexation chemistry for uranium extraction from the sea.

Validation methodology to analyze the temperature-dependent heat path of a 4-chip LED module using a finite volume simulation

Thermal management in the solid-state lighting sector has become a main issue, due to reliability and efficiency issues. Herein, thermal structure function analysis provides a powerful tool to understand the heat transfer inside operated light emitting diode (LED) modules. In this paper a combined approach of simulation and experiment, as a heat path analysis of a LED module based on four flip chip LEDs, is presented. A validated simulation was used to visualize on the one hand the heat path as isothermals and on the other hand to show an alternative approach of the electrical transient correction. In addition to that, the structure function analysis also included the consideration of influence parameters in terms of different operating conditions (e.g. heat sink temperature, heating current, the use of different thermal interface materials between the device and the heatsink). This was investigated by the statistical Design of Experiments (DOE) approach. The DOE dissected the effect of each input variation to different features of the structure functions. An experimental setup showed, that the temperature of the heat sink caused the dominating effect on the thermal properties of the device. Finally numerical simulation confirmed that these effects came from the temperature dependencies of the thermal conductivities.

Interactive foresight simulation

The Combined Simulation Approach (CSA) is a way to evaluate risks and address potential unforeseen problems in a more interactive way than what is often observed in practice in companies or sectors. The approach is based on a combination of scenario analysis and discrete-event computer simulation with which the strategies can be continuously developed. The contribution of this paper is to narrow the knowledge gap between strategic, tactical and operational levels of an organization. The paper demonstrates how it is possible to work proactively with both the breadth and depth of strategies using a Danish knowledge intensive company as an example.

Investigation of deficit irrigation strategies combining SVAT-modeling, optimization and experiments

Irrigation farming is the greatest consumer of the Earth’s freshwater resources. In the light of an increasing water demand caused by growing population, effective methods are required that use the available water resources efficiently and increase the overall productivity of irrigation systems. In this contribution, a combined approach of simulation–optimization and experiments was applied to investigate and evaluate two different irrigation strategies and their parameters for maize with the objective to achieve high water productivity (WP) with high reliability. Thereby, a soil–vegetation–atmosphere transfer (SVAT) model was used to simulate crop growth and soil water transport, together with task-specific optimization algorithms to determine optimal parameters for irrigation schedules and sensor-based full and deficit irrigation controls. An intensively monitored 3-year irrigation experiment was conducted for testing different irrigation designs and verifying the simulation–optimization approach. A new sensor for measuring soil water potentials from pF 0 to pF 7 allowed for applying optimized irrigation thresholds greater than 1,000 hPa. Attained \(\mathrm{WP}_{\mathrm{ET}}\) from the irrigation experiments were generally high and ranged from 1.8 to \(2.3\hbox { kg m}^{-3}\). The impact of irrigation system parameters on WP, such as irrigation interval, sensor depth, number of irrigation thresholds, and the soil’s initial water content were evaluated and discussed. Results indicate that thresholds beyond the measurement range of commonly used tensiometers are feasible. Furthermore, the combination of SVAT-modeling and optimization has the potential to systematically investigate and improve irrigation systems as well as to reduce the number of required field experiments.

A Simulation-Based Ergonomic and Operational Analysis for the Improvement of a Fish Processing Factory Ship

Abstract This article presents a case study of general ergonomic and operational improvement of the on board process in factory ships. The process includes several lines with automatic and manual operations for processing caught fish as different products. It is a complex system with a great variety of operation possibilities. An exploratory simulation model of the plant and the human tasks is developed as a way to identify improvement opportunities. A combined simulation approach has been adopted for the characterization and improvement of the process comprising (i) a Discrete Event Simulation (DES) to develop the analysis of the production system and experiment with operational rules and (ii) a DHM-based study to analyse the present ergonomic conditions on the manual operations and to propose alternative workstation designs that could lead to effective and ergonomic improvement. As a result, we could characterize the process efficiency in different production scenarios, the organizational effects in the packing workstation and the ergonomic and operational assessment of the packing operations.

A new strategy for simulation of electrochemical mechanisms involving acute reaction fronts in solution under spherical or cylindrical diffusion

In this paper we present a combined simulation approach for solving complex electrochemical kinetic problems at (hemi)spherical and (hemi)cylindrical electrodes based on the simultaneous application of analytical conformal coordinate transformations to accurately treat the diffusional transport and adaptive grid compression to locally increase the accuracy of the approximation of acute reaction fronts. This strategy is shown to be very efficient and leads to extremely accurate results both for steady state and transient situations and is equally powerful for both pure diffusion and that complicated by severe kinetic distortions.

The Combined Simulation Approach of Atomistic and Continuum Models for the Thermodynamics of Lysozyme Crystals

We have studied the thermodynamic properties of hen egg white lysozyme crystals using a novel simulation method combining atomistic Monte Carlo simulation to calculate van der Waals interactions and the boundary element method to solve the Poisson-Boltzmann equation for the electrostatic interactions. For computational simplicity, we treat the protein as a rigid body, using the crystallographic coordinates of all non-hydrogen atoms of the protein to describe the detailed shape. NVT Monte Carlo simulations are carried out for tetragonal and orthorhombic crystals to obtain the van der Waals energy, incorporating an implicit solvation effect. For crystal phases, an optimally linearized Poisson-Boltzmann equation is used to include the effect of the Donnan equilibrium of the salt ions. The Helmholtz energy is obtained from expanded ensemble Monte Carlo simulations. By using the force field parameters that had previously been tuned for the solution properties, reasonable agreement with experiment is found for the crystallization energy of the tetragonal form. The prediction of the entropy is also reasonable with a slight underestimation suggesting the release of a few water molecules per protein during the crystallization. However, the predictions of the properties of the orthorhombic crystal are poor, probably due to differences in the solvation structure as indicated by experiments, and also as a result of the approximate force field used.