| 1. |
- Kannan, Ananda Subramani, 1989, et al.
(författare)
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A continuum-based multiphase DNS method for studying the Brownian dynamics of soot particles in a rarefied gas
- 2019
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509. ; 210
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Tidskriftsartikel (refereegranskat)abstract
- In the mitigation of particulate matter (PM) using filters, the interplay between particle motion, geometry and flow conditions determines the overall performance. In such flows, molecular effects on the particle motion manifest as impeded momentum transfer and a meandering Brownian motion. Other particles and walls induce hydrodynamic interactions, which may further influence PM nucleation, growth and aggregation. Here, we formulate a multiphase direct numerical simulation framework to investigate these complex flows by including the molecular interactions in a consistent manner. The basis for this framework is a coupling between the Langevin description of particle motion with a mirroring immersed boundary method. We show that the method is able to capture the diffusion dynamics of a Brownian particle, including its transition from a particle-inertia dominated, correlated ballistic regime to a non-correlated diffusive one, and that the method also can be used to reproduce the meandering motion of realistic soot particles.
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| 2. |
- Kannan, Ananda Subramani, 1989, et al.
(författare)
-
A novel multiphase DNS method for the resolution of Brownian motion in a weakly rarefied gas using a continuum framework
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we formulate an Immersed boundary based direct numerical simulation (DNS) technique for resolving the particle-fluid coupling between a nano-particle and a (weakly) rarefied gas. Such a method resolves the mobility of these solid particles by incorporating the hydrodynamics of the fluid more rigorously within the conventional Langevin description of the system. We analyse the consequences of resolving the subsequent Brownian motion of spherical soot-like hydrocarbon (HC) nano-particles in an unbounded domain using such a framework. The proposed method is able to capture the transition from a particle-inertia dominated (highly correlated) ballistic regime (t^2) to a non-correlated diffusive one (2Dt as given by the Stokes-Einstein relation) and further accurately estimate the resulting diffusivity of the nano-particle. This method can be used within any multiphase DNS framework to reproduce the meandering motion of soot-like Brownian particles under similar conditions.
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| 3. |
- Eleftheriou, Orfeas, 1994, et al.
(författare)
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CFD Simulation and 3D Visualization on Cultural Heritage sites: The Castle of Mytilene
- 2022
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a CFD and 3D Visualization pipeline to simulate wind flow over a heritage site and then visualize the results. As case study, a coarse 3D geometry model of the Fortress of Mytilene, Lesvos island, Greece and its surrounding was generated from open access Digital Elevation Models. The CFD simulation of the air flow on the wider heritage site area was performed using the steady-state version of the in-house flow solver IBOFlow (Immersed Boundary Octree Flow Solver) developed at Fraunhofer-Chalmers Research Centre. All the simulations were completed considering the mean wind direction and wind speed during the last 22 years from actual weather data retrieved from Open Weather Map. The visualization results were achieved through Unreal Engine, using built-in visualization tools and a tailored-made plugin to visualize the air flow over the monument and on the monument’s wall. As discussed in the conclusion section, the overall process proposed in this paper can be implemented for an initial assessment of the effect of environmental parameters over any heritage site and moreover, it may form the basis for valuable assistive tool for conservators and engineers.
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| 4. |
- Forssén, Jens, 1968, et al.
(författare)
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An urban planning tool demonstrator with auralisation and visualisation of the sound environment
- 2020
-
Ingår i: Proceedings of the FA2020 Conference. ; , s. 869-871
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Konferensbidrag (refereegranskat)abstract
- The paper presents findings from a recent project about the development of a demonstrator of an urban planning tool that includes auralised sounds as well as visualisations of sound propagation and facade noise levels linked to health impact. In urban development projects, the sound environment is one of the key elements, but often enters late in the planning process. As a result, even if the noise regulations are fulfilled, the potentially good sound environment may suffer unnecessary quality reductions. In addition, the standard ways of presenting and analysing the situations, using noise levels and noise maps, has potential for improvement, especially considering the transdisciplinary approaches to planning that are increasing in use. The tool aims to simplify the usage also at early stage planning, including scenario analysis, as well as to facilitate the urban planners' understanding of the sound environment and its effects. The paper presents results from the development of the demonstrator, reflecting on auralisation as well as on multiple aspects of visualisation including grid noise maps, health-related facade noise levels and choice of colour scales.
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| 5. |
- Gonzalez Caceres, Alex Arnoldo, 1982, et al.
(författare)
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Towards digital twinning for multi-domain simulation workflows in urban design: a case study in Gothenburg
- 2024
-
Ingår i: Journal of Building Performance Simulation. - 1940-1493 .- 1940-1507. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- This work proposes an automated workflow using digital twinning for multi-domain environmental performance analysis of urban developments. Digital twins can potentially provide a common basis for multi-domain simulations and help overcome data availability and interoperability issues. The proposed workflow consists of five steps: (1) creating a procedural urban 3D model, (2) generating design alternatives parametrically, (3) exporting the context and each design alternative to each simulation tool, (4) running simulations for wind comfort, energy demand, and noise for each design alternative, and (5) combining and visualizing the simulation results using the digital twin. The workflow was applied to a neighbourhood in Sweden, the resultsreveal significant reduction in manual work when applying multiple simulation software for different domains. This is one step forward in streamlining the workflow for urban analysis, crucial for multi-domain optimization. In the future, further domains and simulation tools can be added to the workflow.
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| 6. |
- Ketzler, Bernd, 1982, et al.
(författare)
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Digital Twins for Cities: A State of the Art Review
- 2020
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Ingår i: Built Environment. - : Alexandrine Press. - 0263-7960. ; 46:4, s. 547-573
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Tidskriftsartikel (refereegranskat)abstract
- During the last decades, a variety of digital tools have been developed to support both the planning and management of cities, as well as the inclusion of civic society. Here, the concept of a Digital Twin – which is rapidly emerging throughout many disciplines due to advances in technology, computational capacities and availability of large amounts of data – plays an important role. In short, a digital twin is a living virtual model, a connected digital representation of a physical system and has been a central concept in the manufacturing industry for the past decades. In this article, we review the terminology of digital twins for cities and identify commonalities and relations to the more established term 3D city models. Our fi ndings indicate an increasing use of the term digital twin in academic literature, both in general and in the context of cities and the built environment. We fi nd that while there is as yet no consensus on the exact defi nition of what constitutes a digital twin, it is increasingly being used to describe something that is more than a 3D city model (including, e.g. semantic data, real-time sensor data, physical models, and simulations). At the same time, the term has not yet replaced the term 3D city model as the most dominant term in the 3D GIS domain. By looking at grey literature we discuss how digital twins for cities are implemented in practice and present examples of digital twins in a global perspective. Further, we discuss some of the application areas and potential challenges for future development and implementation of digital twins for cities. We conclude that there are signifi cant opportunities for up-scaling digital twins, with the potential to bring benefi ts to the city and its citizens and clients.
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| 7. |
- Kolibarov, N., et al.
(författare)
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Roof Segmentation Towards Digital Twin Generation in LoD2+Using Deep Learning
- 2022
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Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963 .- 2405-8963. ; 55:11, s. 173-178
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Konferensbidrag (refereegranskat)abstract
- There is an increasing need for digital twins of cities and their base maps, 3D city models. Creating and updating these twins is not an easy task, so automating and streamlining the process is a field of active research. A significant part of the urban geometry is residential buildings and their roofs. Modeling of roofs for urban buildings can be divided into three main areas - building detection, roof recognition and building reconstruction. The building and roofs are segmented with the help of machine learning and image processing. Afterwards the extracted information is used to generate parametric models for the roofs using methods from computational geometry. The goal is to create correct virtual models of roofs belonging to many different types of buildings. In this study, a supervised deep learning approach is proposed for the segmentation of roof edges from a single orthophoto. The predicted features include the linear elements of roofs. The experiments show that, despite the small amount of training data, even in the presence of noise, the proposed method performs well on semantic segmentation of roofs with different shapes and complexities. The quality of the extracted roof elements for the test area is about 56% and 71% for mean intersection over union (IOU) and Dice metric scores, respectively. Copyright (C) 2022 The Authors.
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| 8. |
- Latino, Fabio, 1990, et al.
(författare)
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Virtual City@Chalmers: Creating a prototype for a collaborative early stage urban planning AR application
- 2019
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Ingår i: Proceedings of the 7th Regional International Symposium on Education and Research in Computer Aided Architectural Design in Europe. - 9788772100296 ; , s. 15-24
-
Konferensbidrag (refereegranskat)abstract
- Contemporary urban planning require multi-stakeholder collaboration to create liveable, accessible and resilient cities. Information and communications technologies can play an important role. This paper presents and discusses the development of a prototype for an indoor multi-stakeholder augmented reality (AR) application to support collaborative design in early stage urban planning. The prototype is integrated into VirtualCity@Chalmers, a platform for modeling, simulation, and visualization of urban environments. Based on a user-centered approach, four main steps were carried out: literature study, interview study, development of guidelines, and development of the first version of a collaborative AR prototype. The guidelines for the prototype development address design and layout, collaboration, analysis, and object creation and manipulation. At the current state of development, the AR application allows users to visualize a projection of three-dimensional assets over a flat surface. Further research will focus on user testing and integration of simple Computational Fluid Dynamics simulations.
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| 9. |
- Logg, Anders, 1976, et al.
(författare)
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Digital Twin Cities: Multi-Disciplinary Modeling and High-Performance Simulation of Cities
- 2022
-
Ingår i: ECCOMAS NEWSLETTER. ; June 2022, s. 26-31
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The digital twin concept has virtually exploded in recent years, as evidenced by the exponentially growing number of scientific articles making use of the concept. The concept originates from the manufacturing industry where the use of CAD models enables the creation of exact digital replicas of components and products. The earliest use of the term dates back to 2003 and is often credited to Grieves and Vickers, but earlier references to the concept can be found; certainly, the understanding that mathematical and, more recently, digital models of physical systems are of enormous importance to both science and engineering dates back centuries. The concept has since spread from the manufacturing industry to other disciplines, such as agriculture, electricity, vessels, manufacturing, construction, cities, healthcare, aerospace, waste, water, transport, and automotive. In this short note, we present an overview of the use of digital twins in the built environment; that is, digital twins of cities and buildings. In this context, the term digital twin is closely linked to the concept of smart cities (or smart buildings). The relation between a digital city twin and a smart city is that the digital twin is the enabling technology for making a city smart. Even if a digital twin is not a sufficient condition for making a city smart, it is a necessary condition.
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| 10. |
- Logg, Anders, 1976, et al.
(författare)
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Modeling and Simulating Cities with Digital Twins
- 2022
-
Ingår i: GIM International. - 1566-9076. ; 36:6, s. 14-17
-
Tidskriftsartikel (refereegranskat)abstract
- The digital twin concept has virtually exploded in recent years, but within the built environment the traditional term has long been ‘3D city model’. However, the digital twin concept is increasingly gaining acceptance as a useful concept that extends beyond 3D city models for not only modelling but also simulating cities. So what are digital twins, how are they being used, and what challenges are involved?
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| 11. |
- Mitkov, Radostin, et al.
(författare)
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The Role of Computational Fluid Dynamics within City Digital Twins: Opportunities and Challenges
- 2024
-
Ingår i: ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences. - 2194-9042 .- 2194-9050. ; 10:4/W4-2024, s. 131-136
-
Konferensbidrag (refereegranskat)abstract
- The rapid urbanization trend has led to complex challenges in managing urban environments, ranging from energy consumption to environmental quality and public health. In response, the concept of city digital twins has emerged, offering a promising approach to understanding and managing urban complexity. City digital twins utilize real-time data and simulations to create virtual replicas of urban environments, enabling stakeholders to analyze, optimize, and make informed decisions about various aspects of city life. Computational Fluid Dynamics (CFD) plays a crucial role within city digital twins, offering capabilities to simulate wind flow dynamics, air quality, and pollutant dispersion within urban environments. This paper explores the opportunities and challenges of integrating CFD within city digital twins. Opportunities include optimizing urban planning and design processes, enhancing environmental quality, and improving public health outcomes. However, challenges such as data integration and quality, implementation constraints, computational complexity, and communication of results must be addressed to realize the full application potential of CFD in urban environments. Despite these challenges, the integration of CFD within city digital twins holds promise for creating more livable, sustainable, and resilient cities in the face of urbanization and climate change.
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| 12. |
- Mitkov, R., et al.
(författare)
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Using the Octree Immersed Boundary Method for urban wind CFD simulations
- 2022
-
Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963 .- 2405-8963. ; 55:11, s. 179-184
-
Konferensbidrag (refereegranskat)abstract
- This paper describes the initial steps in a larger effort to perform verification and validation (V&V) of wind simulations in an urban environment. The presented work uses data from wind tunnel experiments on a simplified urban area to assess the performance of the steady-state RANS octree immersed boundary flow solver IBOFlow (R). Verification and validation activities are indispensable in computational modelling, because they address the issue about the trustworthiness of models directly. This is particularly so in the modelling of complex systems such as urban environments. The results of the early V&V work are presented, together with a discussion on different aspects of the experimental and modelling settings. A key contribution this work, which is planned as a first in a series of V&V publications, is the identification of concrete future actions to address the issues of trust in urban wind model predictions. Copyright (C) 2022 The Authors.
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| 13. |
- Naserentin, Vasilis, 1981, et al.
(författare)
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A Review and Case Study of Neural Network Techniques for Automated Generation of High Level-of-Detail 3D City Models
- 2023
-
Ingår i: Springer Proceedings in Mathematics and Statistics. - 2194-1009 .- 2194-1017. - 9783031358708
-
Konferensbidrag (refereegranskat)abstract
- The growing interest in creating digital twins of cities has sparked a surge in the development of detailed 3D models. In this paper we examine the current state-of-the-art in generating high-resolution 3D models of cities using neural network techniques. Additionally, we showcase the outcomes of two case studies that demonstrate the practical applications of these techniques in 3D city model generation. The first case study focuses on rooftop segmentation using publicly available Swedish cadastral data, while the second case study explores façade feature extraction using Google Street View data.
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| 14. |
- Naserentin, Vasilis, 1981, et al.
(författare)
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Combining Open Source and Commercial Tools in Digital Twin for Cities Generation
- 2022
-
Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963 .- 2405-8963. ; 55:11, s. 185-189
-
Konferensbidrag (refereegranskat)abstract
- Evidently, Smart Cities are on the rise and there is an increasing need for digital twins of these complex environments and their corresponding 3D models. The creation and maintenance of such twins is a time consuming task, since cities are living evolving organisms. In this paper we are presenting work done within the Digital Twin Cities Centre (DTCC) in Sweden in the field of automated 3D city model generation. We showcase a novel method of combining open source and commercial software for creating digital twins of any urban context in a procedural way from raw input data and using Unreal Engine as a visualization front-end. We combine two different workflows, one based on the commercial software suite Feature Manipulation Engine and in parallel we utilize the open source code developed within the Centre, dubbed DTCC Builder. The assets created can be used in urban planning, multiphysics continuum mechanics simulations and for visualization and illustration on a 3D scale. By using, in a complementary way, established commercial software and state of the art open source C++ code we manage to utilize the quality of life features the first provides, while assigning the demanding tasks of comforming mesh generation to the former. The longer term goal is (nearly) real-time mesh digital twinning of any city and user interaction with the 3D assets provided. Copyright (C) 2022 The Authors.
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| 15. |
- Naserentin, Vasilis, 1981, et al.
(författare)
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DTCC Builder: A mesh generator for automatic, efficient, and robust mesh generation for large-scale city modeling and simulation
- 2023
-
Ingår i: Journal of Open Source Software. - 2475-9066. ; 8:86
-
Tidskriftsartikel (refereegranskat)abstract
- Digital Twin Cities Centre (DTCC) Builder is a mesh generator for automatic, efficient, and robust mesh generation for large-scale city modeling and simulation. Using standard and widely available raw data sources in the form of point clouds and cadastral data, DTCC Builder generates high-quality 3D surface and volume meshes, suitable for both visualization and simulation. In particular, DTCC Builder is capable of generating large-scale, conforming tetrahedral volume meshes of cities suitable for finite element (FEM) simulation.
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| 16. |
- Somanath, Sanjay, 1994, et al.
(författare)
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Towards Urban Digital Twins: A Workflow for Procedural Visualization Using Geospatial Data
- 2024
-
Ingår i: Remote Sensing. - 2072-4292. ; 16:11
-
Tidskriftsartikel (refereegranskat)abstract
- A key feature for urban digital twins (DTs) is an automatically generated detailed 3D representation of the built and unbuilt environment from aerial imagery, footprints, LiDAR, or a fusion of these. Such 3D models have applications in architecture, civil engineering, urban planning, construction, real estate, Geographical Information Systems (GIS), and many other areas. While the visualization of large-scale data in conjunction with the generated 3D models is often a recurring and resource-intensive task, an automated workflow is complex, requiring many steps to achieve a high-quality visualization. Methods for building reconstruction approaches have come a long way, from previously manual approaches to semi-automatic or automatic approaches. This paper aims to complement existing methods of 3D building generation. First, we present a literature review covering different options for procedural context generation and visualization methods, focusing on workflows and data pipelines. Next, we present a semi-automated workflow that extends the building reconstruction pipeline to include procedural context generation using Python and Unreal Engine. Finally, we propose a workflow for integrating various types of large-scale urban analysis data for visualization. We conclude with a series of challenges faced in achieving such pipelines and the limitations of the current approach. However, the steps for a complete, end-to-end solution involve further developing robust systems for building detection, rooftop recognition, and geometry generation and importing and visualizing data in the same 3D environment, highlighting a need for further research and development in this field.
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| 17. |
- Somanath, Sanjay, 1994, et al.
(författare)
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Towards Urban Digital Twins: A Workflow for Procedural Visualization Using Geospatial Data
- 2024
-
Ingår i: Remote Sensing. - 2072-4292. ; 16:11
-
Tidskriftsartikel (refereegranskat)abstract
- A key feature for urban digital twins (DTs) is an automatically generated detailed 3D representation of the built and unbuilt environment from aerial imagery, footprints, LiDAR, or a fusion of these. Such 3D models have applications in architecture, civil engineering, urban planning, construction, real estate, Geographical Information Systems (GIS), and many other areas. While the visualization of large-scale data in conjunction with the generated 3D models is often a recurring and resource-intensive task, an automated workflow is complex, requiring many steps to achieve a high-quality visualization. Methods for building reconstruction approaches have come a long way, from previously manual approaches to semi-automatic or automatic approaches. This paper aims to complement existing methods of 3D building generation. First, we present a literature review covering different options for procedural context generation and visualization methods, focusing on workflows and data pipelines. Next, we present a semi-automated workflow that extends the building reconstruction pipeline to include procedural context generation using Python and Unreal Engine. Finally, we propose a workflow for integrating various types of large-scale urban analysis data for visualization. We conclude with a series of challenges faced in achieving such pipelines and the limitations of the current approach. However, the steps for a complete, end-to-end solution involve further developing robust systems for building detection, rooftop recognition, and geometry generation and importing and visualizing data in the same 3D environment, highlighting a need for further research and development in this field.
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| 18. |
- Stahre Wästberg, Beata, 1974, et al.
(författare)
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Visual conflicts - Challenges in combining rich volumetric 3D-data in a realistic VR city model
- 2021
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper presents a work in progress on how to visualize the impact of vegetation on urban air quality in a virtual city model, explorable using virtual reality (VR). The transdisciplinary project CityAirSim - Visualizing and modelling urban air quality - influence of vegetation, building morphology and traffic emissions develops a modelling framework to simulate the effects of vegetation, buildings and traffic strategies on air pollution, in order to understand the synergies and conflicts between these factors. The resulting data will be visualized in a VR-application allowing interactive exploration. Two primary target groups for the VR-application are high school students and urban planners. We aim for the tool to be used in teaching, e.g., in environmental science, as well as in communication with the public in exhibition environments, such as science centers. This paper focuses on how we should visualize invisible air pollution in an otherwise realistic urban setting to facilitate understanding. One important aspect to consider is to create a visual balance between data visualization and the visualization of the built environment in the model. Another aspect is to define the appropriate levels of data visualization and abstraction of representation to use, without losing richness of information.
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| 19. |
- Thuvander, Liane, 1970, et al.
(författare)
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Towards spatial integration of qualitative data for urban transformation – challenges with automated geovisualization of perception of urban places
- 2020
-
Ingår i: IOP Conference Series: Earth and Environmental Science. - : IOP Publishing. - 1755-1307 .- 1755-1315. ; 588:5
-
Konferensbidrag (refereegranskat)abstract
- Urban planning needs to face and integrate ecological, social, and economic aspects of city living. So far, attempts to integrate different urban simulation models into one technical platform have focused on quantitative data. The aim of this paper is to present the preparation for an automated method to spatially integrate and visualize interview-based qualitative data on the perception of urban places into a virtual platform. The Gothenburg suburb of Hammarkullen is used as a case study. Two CAQDAS software, NVivo and Atlas.ti, were tested. In both software, locations and urban qualities were coded and clustered. Visualization strategies such as information tree structures, geo-coded quotations, spatial word clouds, linked to 2D maps and 3D environments were developed. Results identify the challenges to overcome and show limitations of the software in terms of creating graphs and relationships as well as automated geocoding of data to maps. The project offers a step towards the integration of qualitative (social) data into digital environments that can be scaled up. By that, it contributes with a new dimension of analysis of urban environments which is necessary for sustainable transformation of cities.
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| 20. |
- Ögren, Mikael, et al.
(författare)
-
Visualisation of traffic noise exposure and health impact in a 3D urban environment
- 2021
-
Ingår i: Paper collection of the ICBEN 2021 Congress.
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Konferensbidrag (refereegranskat)abstract
- It is becoming increasingly common to work with urban planning using 3D visualisation tools. In the project DemoVirPEN a research team with participation from different research fields cooperated to create a demonstration concept for visualising traffic noise and the associated health impact in a 3D graphics environment. The project included participation from the following fields; 3D modelling and mapping, traffic noise calculation, auralisation, urban planning and architecture and health impact of noise exposure. The final product of the project is summarised in a film clip that illustrates the main results by visualising and auralising traffic in different configurations from different perspectives. A few key points are visualising short time frames (single vehicle passage) versus yearly average (noise map), and impact of changes such as removing or modifying traffic flows and buildings.
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