| 1. |
- Johansson, August, et al.
(författare)
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A Multimesh Finite Element Method for the Stokes Problem
- 2020
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Ingår i: Lecture Notes in Computational Science and Engineering. - Cham : Springer International Publishing. - 1439-7358 .- 2197-7100. ; 132, s. 189-198, s. 189-198
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Konferensbidrag (refereegranskat)abstract
- The multimesh finite element method enables the solution of partial differential equations on a computational mesh composed by multiple arbitrarily overlapping meshes. The discretization is based on a continuous–discontinuous function space with interface conditions enforced by means of Nitsche’s method. In this contribution, we consider the Stokes problem as a first step towards flow applications. The multimesh formulation leads to so called cut elements in the underlying meshes close to overlaps. These demand stabilization to ensure coercivity and stability of the stiffness matrix. We employ a consistent least-squares term on the overlap to ensure that the inf-sup condition holds. We here present the method for the Stokes problem, discuss the implementation, and verify that we have optimal convergence.
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| 2. |
- Johansson, August, et al.
(författare)
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Multimesh finite elements with flexible mesh sizes
- 2020
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Ingår i: Computer Methods in Applied Mechanics and Engineering. - : Elsevier BV. - 0045-7825 .- 1879-2138. ; 372
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Tidskriftsartikel (refereegranskat)abstract
- We analyze a new framework for expressing finite element methods on arbitrarily many intersecting meshes: multimesh finite element methods. The multimesh finite element method, first presented in Johansson et al. (2019), enables the use of separate meshes to discretize parts of a computational domain that are naturally separate; such as the components of an engine, the domains of a multiphysics problem, or solid bodies interacting under the influence of forces from surrounding fluids or other physical fields. Furthermore, each of these meshes may have its own mesh parameter. In the present paper we study the Poisson equation and show that the proposed formulation is stable without assumptions on the relative sizes of the mesh parameters. In particular, we prove optimal order a priori error estimates as well as optimal order estimates of the condition number. Throughout the analysis, we trace the dependence of the number of intersecting meshes. Numerical examples are included to illustrate the stability of the method.
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| 3. |
- 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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| 4. |
- Logg, Anders, 1976, et al.
(författare)
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Finite element simulation of physical systems in augmented reality
- 2020
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Ingår i: Advances in Engineering Software. - : Elsevier BV. - 0965-9978 .- 1873-5339. ; 149
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Tidskriftsartikel (refereegranskat)abstract
- We present a system for immersive and interactive physics simulation in augmented reality, implemented as an application on the Microsoft HoloLens. The system allows a user to simulate physical phenomena in real-world geometries by scanning the surroundings and automatically creating a finite element discretization (mesh). The system also provides a user interface based on voice commands for specification of boundary conditions and source terms, and for immersive visualization of simulation results. All computations are carried out on the HoloLens. The current implementation, named HoloFEM, demonstrates the application of augmented reality simulation for the time-dependent advection-diffusion equation. In the current work, we consider a simplified model problem with simplified parameters and data. The model is however still conceptually applicable to the simulation of indoor climate (temperature and air quality), which has implications for interactive HVAC (heating, ventilation, and air conditioning) simulation.
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| 5. |
- Stahre Wästberg, Beata, 1974, et al.
(författare)
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Visualisering och auralisering av buller i stadsmiljö
- 2020
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Ingår i: Bygg & teknik. - 0281-658X. ; 3, s. 8-12
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Inom dagens stadsplanering används oftast 2D-kartor för att visa beräknade värden för framtida bullernivåer. Dessa kartor kan ibland vara svåra att tolka. För att öka förståelsen och underlätta kommunikationen mellan olika aktörer inom planeringsprocessen, har vi inom forskningsprojektet DemoVirPEN på Chalmers och Göteborgs universitet utvecklat en prototyp av ett verktyg för visualisering och auralisering (ljudsimulering) av buller från vägtrafik i en stadsmodell.
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| 6. |
- 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
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Ingår i: IOP Conference Series: Earth and Environmental Science. - : IOP Publishing. - 1755-1307 .- 1755-1315. ; 588:5
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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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