Open-source Simulation Software Research Articles

Implementation of an IoT- and Cloud-based Digital Twin for Real-Time Decision Support in Port Operations

Seaborne trade volumes are growing and the resulting traffic load on the road infrastructure in port areas calls for new solutions to improve handling and coordination of vehicles and shipments. In this contribution, a digital twin for truck dispatching operator assistance is presented, which enables the determination of optimal dispatching policies using simulation-based performance forecasts. Proprietary simulation software with limited interfaces, the application deployment in demanding industrial environments, and the integration of real-time sensor information represent three major challenges when realizing digital twin applications for logistics systems. This implementation, therefore, uses an extensible open-source simulation package and it is coupled with an IoT-platform for easy integration of real-time information. The digital twin is deployed as a cloud-based service, allowing for simple deployment and scalability.

Mixing study of non-spherical particles using DEM

In the last decade, granular flows have been studied extensively using DEM simulations. But only a little work has been done using non-spherical or real-shape particles even in the latest publications using powerful simulation tools making such study a need of the hour. This is important because the understanding of these particle shapes is crucial for design and development of real-life industrial mixers. In this work, we employed DEM (discrete element method) approach and used open-source simulation software LIGGGHTS to study the flow and mixing behaviour of polydisperse, non-spherical cohesionless particles in a cylindrical tank mixer. The mixer was agitated by using a four-bladed impeller and a blade-rake angle of 135°. We studied the flow and mixing behaviour by analysing particle velocities, contact forces and mixing performance. The mixing was quantified using a latest subdomain-based mixing index introduced by [1]. Different particle shapes were employed and expressed in terms of circularity/sphericity. We used seven different shapes in addition to spherical shape used for benchmarking. It is learnt that as we sway from circularity or sphericity, the mixing performance decreases. The complex (or in fact the real) shape particles are observed to have lower mixing performance compared to spherical particles under similar conditions.

Optimal B-spline Mapping of Flow Imaging Data for Imposing Patient-specific Velocity Profiles in Computational Hemodynamics.

Objective:We propose a novel method to obtainmap patient-specific blood velocity profiles (obtained from imaging data such as 2D flow MRI or 3D colour Doppler ultrasound) and map them to geometric vascular models suitable to perform CFD simulations of haemodynamics. We describe the implementation and utilisation of the method within an open-source computational hemodynamics simulation software (CRIMSON).Methods:tThe proposed method establishes point-wise correspondences between the contour of a fixed geometric model and time-varying contours containing the velocity image data, from which a continuous, smooth and cyclic deformation field is calculated. Our methodology is validated using synthetic data, and demonstrated using two different in-vivo aortic velocity datasets: a healthy subject with normal tricuspid valve and a patient with bicuspid aortic valve.Results:We compare the performance of our method with results obtained with the state-of-the-art Schwarz-Christoffel method, in terms of preservation of velocities and execution time. Our method is as accurate as the Schwarz-Christoffel method, while being over 8 times faster. The proposed method can preserve either the flow rate or the velocity field through the surface, and can cope with inconsistencies in motion and contour shape.Conclusions:Our results show that the method is as accurate as the Schwarz-Christoffel method in terms of maintaining the velocity distributions, while being more computationally efficient.Our mapping method can accurately preserve either the flow rate or the velocity field through the surface, and can cope with inconsistencies in motion and contour shape.Significance:The proposed method and its integration into the CRIMSON software enable a streamlined approach towards incorporating more patient-specific data in blood flow simulations.

Development of a VR capable virtual laboratory framework

The aim of this paper is to introduce the design steps and implementation details of a system, which combines modern web-technologies and open-source simulation software to create a virtual laborat...

Melt Pool Analysis and Mesoscale Simulation of Laser Powder Bed Fusion Process (L-PBF) with Ti-6Al-4V Powder Particles

The laser powder bed fusion (L-PBF) process is accompanied by rapid melting and solidification that results in intense thermocapillary convection within the melt pool. Open-source particle simulation software was utilized to generate a single layer of spherical powder particles of variable diameter. Considering the importance of particle size and the particle size distribution (PSD) in the L-PBF process, three distinct categories of PSD were generated with identical settings. A three-dimensional (3D) thermofluid model was developed in this study, incorporating the generated layer of powder particles of nonuniform size over a thick substrate. A moving volumetric heat source was applied to melt a single track in the powder layer using a user-defined function in FLUENT software. Temperature-dependent material properties including variable surface tension were considered in the computation. The numerical model was used to simulate Ti-6Al-4V powder particles to observe the melt pool flow dynamics. Presence of particles of smaller diameter in the powder mix supported consistent and continuous melt pool flow, while any kind of void enhanced fluid convection in the downward direction, causing a temporal increase in melt pool depth.

SIMULATION OPTIMIZATION IN DOSING PROCESS CONTROL SYSTEM IN REAL TIME IN A FREE AND OPEN-SOURCE SOFTWARE

ABSTRACT The purpose of this work is to implement an on-line control system able to adjust the production in real time applying a simulation model with algorithmic optimization and data transfer for a programmable logic controller. The Solver tool of the Excel software was integrated into a simulation software used to find the optimal dosing of input aggregates in a Hot Mix Asphalt process. Tests were carried out in different scenarios; the results demonstrated that the proposed control was effective, leading to a possible improvement in the quality of the product, enabling it to be kept within the specifications desired for most of the time. Besides, the proposed solution appeared to be simple and accessible for small companies as it applies the Excel software and a free and open-source discrete event simulation software.

DigR: a generic model and its open source simulation software to mimic three-dimensional root-system architecture diversity.

Many studies exist in the literature dealing with mathematical representations of root systems, categorized, for example, as pure structure description, partial derivative equations or functional-structural plant models. However, in these studies, root architecture modelling has seldom been carried out at the organ level with the inclusion of environmental influences that can be integrated into a whole plant characterization. We have conducted a multidisciplinary study on root systems including field observations, architectural analysis, and formal and mathematical modelling. This integrative and coherent approach leads to a generic model (DigR) and its software simulator. Architecture analysis applied to root systems helps at root type classification and architectural unit design for each species. Roots belonging to a particular type share dynamic and morphological characteristics which consist of topological and geometric features. The DigR simulator is integrated into the Xplo environment, with a user interface to input parameter values and make output ready for dynamic 3-D visualization, statistical analysis and saving to standard formats. DigR is simulated in a quasi-parallel computing algorithm and may be used either as a standalone tool or integrated into other simulation platforms. The software is open-source and free to download at http://amapstudio.cirad.fr/soft/xplo/download. DigR is based on three key points: (1) a root-system architectural analysis, (2) root type classification and modelling and (3) a restricted set of 23 root type parameters with flexible values indexed in terms of root position. Genericity and botanical accuracy of the model is demonstrated for growth, branching, mortality and reiteration processes, and for different root architectures. Plugin examples demonstrate the model's versatility at simulating plastic responses to environmental constraints. Outputs of the model include diverse root system structures such as tap-root, fasciculate, tuberous, nodulated and clustered root systems. DigR is based on plant architecture analysis which leads to specific root type classification and organization that are directly linked to field measurements. The open source simulator of the model has been included within a friendly user environment. DigR accuracy and versatility are demonstrated for growth simulations of complex root systems for both annual and perennial plants.

Foraging behavior analysis of swarm robotics system

Swarm robotics is a number of small robots that are synchronically works together to accomplish a given task. Swarm robotics faces many problems in performing a given task. The problems are pattern formation, aggregation, Chain formation, self-assembly, coordinated movement, hole avoidance, foraging and self-deployment. Foraging is most essential part in swarm robotics. Foraging is the task to discover the item and get back into the shell. The researchers conducted foraging experiments with random-movement of robots and they have end up with unique solutions. Most of the researchers have conducted experiments using the circular arena. The shell is placed at the centre of the arena and environment boundary is well known. In this study, an attempt is made to different strategic movements like straight line approach, parallel line approach, divider approach, expanding square approach, and parallel sweep approach. All these approaches are to be simulated by using player/stage open-source simulation software based on C and C++ programming language in Linux operating system. Finally statistical comparison will be done with task completion time of all these strategies using ANOVA to identify the significant searching strategy.

Foraging behavior analysis of swarm robotics system

Swarm robotics is a number of small robots that are synchronically works together to accomplish a given task. Swarm robotics faces many problems in performing a given task. The problems are pattern formation, aggregation, Chain formation, self-assembly, coordinated movement, hole avoidance, foraging and self-deployment. Foraging is most essential part in swarm robotics. Foraging is the task to discover the item and get back into the shell. The researchers conducted foraging experiments with random-movement of robots and they have end up with unique solutions. Most of the researchers have conducted experiments using the circular arena. The shell is placed at the centre of the arena and environment boundary is well known. In this study, an attempt is made to different strategic movements like straight line approach, parallel line approach, divider approach, expanding square approach, and parallel sweep approach. All these approaches are to be simulated by using player/stage open-source simulation software based on C and C++ programming language in Linux operating system. Finally statistical comparison will be done with task completion time of all these strategies using ANOVA to identify the significant searching strategy.

Ururau: a free and open-source discrete event simulation software

This paper has the purpose of describing the architecture and operation of Ururau, a software used to create discrete event simulation models based on the Java Simulation Library. Ururau is a free and open-source multiplatform software, which allows the user to develop models in the graphical interface or implement them directly in the source code. This characteristic allows the user to employ it as a tool for modeling and simulation of discrete event systems and also as a learning tool. Thus, an experienced modeler can add specific algorithms to simulation models or new features to the simulator. Also, with access to the source code, a beginner modeler can understand the internal structure of a discrete event simulation software. Initial results have demonstrated this new software’s ability in building small and simple models efficiently.

Development and Use of an Open-Source, User-Friendly Package To Simulate Voltammetry Experiments

An open-source electrochemistry simulation package has been developed that simulates the electrode processes of four reaction mechanisms and two typical electroanalysis techniques: cyclic voltammetry and chronoamperometry. Unlike other open-source simulation software, this package balances the features with ease of learning and implementation and can run on mainstream operating systems. In an elctroanalysis lecture for graduate students, we have simulated the cyclic voltammetry of an electron transfer reaction with varied scan rates. The dynamical concentration profiles were demonstrated in an animation to help students understand the relation between currents and evolving concentration profiles, and the relations between peak currents and scan rates were also discussed.

An integrated platform for design and numerical analysis of shield tunnelling processes on different levels of detail

Building and construction information modelling for decision making during the life cycle of infrastructure projects are vital tools for the analysis of complex, integrated, multi-disciplinary systems. The traditional design process is cumbersome and involves significant manual, time-consuming preparation and analysis as well as significant computational resources. To ensure a seamless workflow during the design and analysis and to minimise the computation time, we propose a novel concept of multi-level numerical simulations, enabling the modelling on different Levels of Detail (LoDs) for each physical component, process information, and analysis type. In this paper, we present SATBIM, an integrated platform for information modelling, structural analysis and visualisation of the mechanised tunnelling process for design support. Based on a multi-level integrated parametric Tunnel Information Model, numerical models for each component on different LoDs are developed, considering proper geometric as well as material representation, interfaces and the representation of the construction process. Our fully automatic modeller for arbitrary tunnel alignments provides a high degree of automation for the generation, the setup and the execution of the simulation model, connecting the multi-level information model with the open-source simulation software KRATOS. The software of SATBIM is organized in a modular way in order to offer high flexibility not only for further extensions, but also for adaptation to future improvements of the simulation software. The SATBIM platform enables practical, yet flexible and user-friendly generation of the tunnel structure for arbitrary alignments on different LoDs, supporting the design process and providing an insight into soil-structure interactions during construction.

The Virtual Mouse Brain: A Computational Neuroinformatics Platform to Study Whole Mouse Brain Dynamics.

Connectome-based modeling of large-scale brain network dynamics enables causal in silico interrogation of the brain's structure-function relationship, necessitating the close integration of diverse neuroinformatics fields. Here we extend the open-source simulation software The Virtual Brain (TVB) to whole mouse brain network modeling based on individual diffusion magnetic resonance imaging (dMRI)-based or tracer-based detailed mouse connectomes. We provide practical examples on how to use The Virtual Mouse Brain (TVMB) to simulate brain activity, such as seizure propagation and the switching behavior of the resting state dynamics in health and disease. TVMB enables theoretically driven experimental planning and ways to test predictions in the numerous strains of mice available to study brain function in normal and pathological conditions.

Multi-scenario optimization approach for assessing the impacts of advanced traffic information under realistic stochastic capacity distributions

In this study, to incorporate realistic discrete stochastic capacity distribution over a large number of sampling days or scenarios (say 30–100days), we propose a multi-scenario based optimization model with different types of traveler knowledge in an advanced traveler information provision environment. The proposed method categorizes commuters into two classes: (1) those with access to perfect traffic information every day, and (2) those with knowledge of the expected traffic conditions (and related reliability measure) across a large number of different sampling days. Using a gap function framework or describing the mixed user equilibrium under different information availability over a long-term steady state, a nonlinear programming model is formulated to describe the route choice behavior of the perfect information (PI) and expected travel time (ETT) user classes under stochastic day-dependent travel time. Driven by a computationally efficient algorithm suitable for large-scale networks, the model was implemented in a standard optimization solver and an open-source simulation package and further applied to medium-scale networks to examine the effectiveness of dynamic traveler information under realistic stochastic capacity conditions.

Obtaining the solid-liquid interfacial free energy via multi-scheme thermodynamic integration: Ag-ethylene glycol interfaces.

The solid-liquid interfacial free energy γsl is an important quantity in wetting, nucleation, and crystal growth. Although various methods have been developed to calculate γsl with atomic-scale simulations, such calculations still remain challenging for multi-component interfaces between molecular fluids and solids. We present a multi-scheme thermodynamic integration method that is inspired by the "cleaving-wall" method and aimed at obtaining γsl for such systems using open-source simulation packages. This method advances two aspects of its predecessor methods. First, we incorporate separate schemes to resolve difficulties when manipulating periodic boundary conditions of the supercell using open-source simulation packages. Second, we introduce a numerical approximation to obtain thermodynamic integrands for complex force fields when an analytical differentiation is not readily available. To demonstrate this method, we obtain γsl for interfaces between Ag(100) and Ag(111) and ethylene glycol (EG). These interfacial free energies mirror interfacial potential energies for each facet. We also estimate entropies of interface formation and these are consistent with theoretical predictions in signs and trends. For the Ag-EG systems, we find that the largest contribution to γsl is the free energy to create the bare metal surfaces. The second-largest contribution to γsl is from the liquid-solid interaction. This user-friendly method will accelerate investigation in a broad range of research topics, such as the thermodynamic effect of structure-directing agents in solution-phase shape-controlled nanocrystal syntheses.

Virtual Micromagnetics: A Framework for Accessible and Reproducible Micromagnetic Simulation

Computational micromagnetics requires numerical solution of partial differential equations to resolve complex interactions in magnetic nanomaterials. The Virtual Micromagnetics project described here provides virtual machine simulation environments to run open-source micromagnetic simulation packages. These environments allow easy access to simulation packages that are often difficult to compile and install, and enable simulations and their data to be shared and stored in a single virtual hard disk file, which encourages reproducible research. Virtual Micromagnetics can be extended to automate the installation of micromagnetic simulation packages on non-virtual machines, and to support closed-source and new open-source simulation packages, including packages from disciplines other than micromagnetics, encouraging reuse. Virtual Micromagnetics is stored in a public GitHub repository under a three-clause Berkeley Software Distribution (BSD) license.

Comparison of measured and simulated performance of natural displacement ventilation systems for classrooms

Children spend the majority of their weekdays in classrooms that often have low indoor air quality and limited financial resources for the initial and running costs of mechanical ventilation systems. Designing effective natural ventilation (NV) systems in schools is difficult due to the intense use of the classroom spaces and the dependence of NV on building geometry and outdoor conditions. Building thermal and airflow simulation tools are fundamental to predict NV system performance in the design phase. These predictions of these tools must be validated (preferably with data from real buildings). This paper presents a set of detailed measurements of buoyancy driven natural DV systems of three classrooms located in two buildings in Lisbon (Portugal). The rooms are located in two educational buildings, a kindergarten and a university, and have different buoyancy driven natural DV systems (with and without chimneys). The experimental measurements are used to validate a three-node DV model implemented on the open-source thermal building simulation software EnergyPlus. The validation results show that the building thermal simulation model tested is able to predict bulk airflow rate with an average error of 16%. In addition, a good agreement is also obtained for the vertical temperature prediction: an average error of 4% corresponding (average deviation of 0.7°C). Analysis of the kindergarten rooms results revealed, that as expected, increasing chimney height from 1 to 4m has a significant positive impact in NV system performance. The performance of natural DV systems depends on the number of thermal plumes in the room. For the same sensible heat load, increasing the number of plumes lowers the average occupied zone air temperature and increases the bulk airflow rate. In light of the complexity of the cases tested, NV with uncontrolled boundary conditions, the results of the comparisons performed between measurements and simulations should contribute to increase confidence in the use of EnergyPlus to simulate buoyancy driven natural DV systems.

Problem Based Learning on Cloud Economics Analysis Using Open Source Simulation

The paper reports the applicablity of open source simulation software called GreenCloud to assist a novel Problem Based Learning in a laboratory environment. The actual case of Indonesia government plan to deploy cloud based data center infrastructure was picked up as the actual case. In such case, cloud economics analysis is required along with technical one. An open source software called GreenCloud is suitebale to perform the simulation and analysis of cloud computing from economics perspective. It was applied into three models of cloud architecture namely Two-Tier, Three-Tier and Three-Tier High Speed and then analyzed in terms of their energy consumptions based on three options of cloud economics scheme, namely i) non energy savings, ii) Dynamics Voltage and Frequency Scaling (DVFS) and iii) Dynamics Shutdown (DNS).

Virtual Design of an Audio Lifelogging System: Tools for IoT Systems

The availability of inexpensive, custom, highly integrated circuits is enabling some very powerful systems that bring together sensors, smart phones, wearables, cloud computing, and other technologies. To design these types of complex systems we are advocating a top-down simulation methodology to identify problems early. This approach enables software development to start prior to expensive chip and hardware development. We call the overall approach virtual design. This book explains why simulation has become important for chip design and provides an introduction to some of the simulation methods used. The audio lifelogging research project demonstrates the virtual design process in practice. The goals of this book are to: explain how silicon design has become more closely involved with system design; show how virtual design enables top down design; explain the utility of simulation at different abstraction levels; show how open source simulation software was used in audio lifelogging. The target audience for this book are faculty, engineers, and students who are interested in developing digital devices for Internet of Things (IoT) types of products.

Study on using design patterns to implement a simulation system for WiMAX network

A network simulator always is an important tool to observe and evaluate the study concept for wireless networks. Considering the restriction of the limited budget, the non-commercial open-source simulation software often becomes the top choice of academia. Since the natures of academic study are innovation and excellence, a simulator frequently encounters that the existing modular functions are inadequate and need to be appended or modified. If a selected simulator inherently has poor architecture, the maintenance, recondition, and expansion of functions will become more difficult and more time-consuming in the future, while it is difficult to understand and reuse by the successors. Therefore, how to select a most suitable simulator is an important issue. In order to make a simulator have flexible architecture and believable results, design patterns are proposed as the norms to design system architecture. To realize this idea, we surveyed six most used simulators, i.e., J-Sim, NS-2, NS-3, OMNet++, OPNET, and QualNet, to ponder their system architectures and design concepts from the source codes and the related literatures of the modular function expansion. We propose a network simulator architecture, named as CCGns, which is a discrete-event virtual network simulator and follows the IEEE 802.16-2009 standard. CCGns obeys the object-oriented design principles and is coded by the Java language. CCGns comprises eight packages for physical layer, medium access control layer, network layer, devices, topologies, events, scheduler, and reports, respectively. The main contribution includes three aspects which propose a scalable MAC messages management and the corresponding architecture, an applicable for multi-hop relay network topology architecture, and a two-stage minimum variance bandwidth allocation algorithm. To the best of our knowledge, this article is not the first one to apply the design patterns for the simulator architectures of wireless network, but we use more design patterns and types than the others and also provide the unified modeling language figures to explain the system architectures. We particularly focus on how the management procedure of control messages influences the time-related performance evaluation metrics, e.g., how the amount and processing time of different control messages affect throughput, packet delay, and packet drop ratio. By using mathematic calculation to verify the simulation results, the proposed system architecture has been proven to possess excellent fidelity.