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Accelerating urban airflow large eddy simulations with generative adversarial networks
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.ORCID iD: 0000-0001-9287-6103
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.ORCID iD: 0000-0003-1285-2334
(English)Manuscript (preprint) (Other academic)
Abstract [en]

This study presents a deep learning framework designed to accelerate LargeEddy Simulation (LES) of airflow in urban environments. The framework leverages physics constrained conditional Generative Adversarial Networks (GANs) trained on instantaneous velocity snapshots from a synthetically generated dataset comprising 130 high-fidelity CFD simulations of simple building configurations. By learning the mapping from early-stage flow fields to their statistically steady-state counterparts, the framework allows the simulation to bypass the lengthy transient averaging phase and predict the final time-averaged fields directly. Two GAN-based architectures are explored: a conventional convolutional model operating on structured uniform grids (Grid-GAN), and a graph-based model (Graph-GAN) that utilizes Graph Neural Networks (GNNs), specifically Graph Attention Networks (GATs), to process unstructured CFD mesh data while preserving native spatial connectivity. Both approaches are integrated into a fully automated pipeline built exclusively on open-source tools, including OpenFOAM for CFD simulations, FreeCAD and ParaView for preprocessing, and PyTorch for deep learning model development and training. Results demonstrate thatthe proposed models can significantly reduce LES computational costs while retaining accuracy in predicting turbulent flow characteristics. The Graph-GAN, in particular, shows enhanced adaptability and physical consistency due to its ability to exploit mesh refinements in critical regions. This worklays the foundation for the development of robust, physics-informed surrogate models and supports the growing integration of deep learning with scientific simulations in fluid mechanics.

Keywords [en]
Deep learning, Computational Fluid Dynamics (CFD), Large Eddy Simulation (LES), urban airflow, Generative Adversarial Networks (GANs), Graph Attention Networks (GATs)
National Category
Fluid Mechanics
Research subject
Civil and Architectural Engineering, Fluid and Climate Theory
Identifiers
URN: urn:nbn:se:kth:diva-369445OAI: oai:DiVA.org:kth-369445DiVA, id: diva2:1995526
Note

QC 20250908

Available from: 2025-09-05 Created: 2025-09-05 Last updated: 2025-09-08Bibliographically approved
In thesis
1. Improving built environment aerodynamics with deep learning
Open this publication in new window or tab >>Improving built environment aerodynamics with deep learning
2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis explores the intersection of deep learning (DL) and computational fluid dynamics (CFD) to improve the modeling and analysis of built environmentaerodynamics. As urbanization accelerates and sustainability challenges intensify, accurate and efficient tools for airflow prediction in cities and buildings are increasingly vital. Traditional CFD methods, while powerful, are computationally demanding and limited by model assumptions, especially in turbulence modeling. This work investigates whether deep learning techniques can enhance both the speed and generalizability of aerodynamic simulations, and whether they can support experimental measurements such as those obtained from wind tunnels. The thesis presents a comprehensive framework that integrates convolutional neural networks (CNNs), graph neural networks (GNNs), and generative adversarial networks (GANs) to accelerate large eddy simulations (LES), reconstruct flow fields, and improve experimental data processing. Notably, GNN-based models are used to operate directly on unstructured CFD meshes, preserving geometric and topological information critical for urban flow predictions. Hybrid approaches that combine physics-based knowledge with data-driven models are also introduced. Applications span both simulated and experimental domains, including a case study on wind tunnel shape optimization using reinforcement learning. While deep learning models showed strong potential for improving both simulation accuracy and speed, the work also highlights important challenges, including the need for better generalization, model interpretability, and the lack of publicly available CFD datasets.The findings suggest that combining deep learning with traditional fluid dynamics offers a promising path forward, especially when supported by open data, physical constraints, and collaborative research efforts. The thesis concludes by outlining directions for future research in physics-informed learning, dataset curation, and real-time integration of predictive models into sustainable urban design.

Abstract [sv]

Denna avhandling utforskar skärningspunkten mellan djupinlärning (DL) och beräkningsströmningsdynamik (CFD) med avsikten att förbättra modellering och analys av aerodynamiken i byggda miljöer. I takt med att urbaniseringen accelererar och hållbarhetsutmaningarna blir större, blir ökar behovet av noggranna och effektiva verktyg för luftflödesprognoser i städer och byggnader. Traditionella CFD-metoder, även om de är kraftfulla, är beräkningskrävande och begränsade av modellantaganden, särskilt inom turbulensmodellering. Detta arbete undersöker om djupinlärningstekniker kan användas för att förbättra både hastigheten och generaliserbarheten hos aerodynamiska simuleringar, och om de kan stödja experimentella mätningar som erhålls från vindtunnlar. Avhandlingen presenterar ett omfattande ramverk som integrerar faltningsneurala nätverk (CNN), grafneurala nätverk (GNN) och generativa adversariella nätverk (GAN) för att accelerera simuleringar av stora virvelsimuleringar (LES), rekonstruera flödesfält och förbättra experimentell databehandling. GNN-baserade modeller används särskilt för att arbeta direkt på ostrukturerade CFD-nät, vilket bevarar geometrisk och topologisk information som är avgörande för förutsägelser av luftflöden i stadsmiljöer. Hybridmetoder som kombinerar fysikbaserad kunskap med datadrivna modeller introduceras också. Tillämpningarna spänner över både simulerade och experimentella områden, inklusive en fallstudie om optimering av en vindtunnels form med hjälp av förstärkningsinlärning (reinforcemnt learning). Djupinlärningsmodeller visade stark potential för att förbättra både simuleringsnoggrannhet och hastighet. Samtidigt belyser arbetet också viktiga utmaningar, såsom behovet av bättre generalisering, modelltolkningsbarhet och även bristen på tillgängliga CFD-data. Resultaten tyder på att kombinationen av maskininlärning med traditionell fluiddynamik erbjuder en lovande väg framåt, särskilt när det finns tillgång till av öppna data, behov med fysiska begränsningar och även gemensamma forskningsinsatser. Avhandlingen avslutas med att skissera riktningar för framtida forskning inom fysikinformerat lärande (PINNs), datasetkurering (dataset curation) och realtidsintegration av prediktiva modeller för en hållbar stadsplanering.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2025. p. 48
Series
TRITA-ABE-DLT ; 2523
Keywords
Aerodynamics, Computational Fluid dynamics, Built Environment, Urban Airflow, Deep Learning, Wind Tunnel, Artificial Intelligence, Neural Networks, Generative Adversarial Networks., Aerodynamiken, Beräkningsströmningsdynamik, Byggda Miljöer, Stadsmiljöer, Djupinlärning, Vindtunnel, Artificiell Intelligens, Neurala Nätverk, Generativa Adversariella Nätverk.
National Category
Other Civil Engineering
Research subject
Civil and Architectural Engineering, Fluid and Climate Theory
Identifiers
urn:nbn:se:kth:diva-369447 (URN)978-91-8106-346-2 (ISBN)
Public defence
2025-09-26, B3, Brinellvägen 23, KTH Campus, public video conference link [MISSING], Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20250905

Available from: 2025-09-05 Created: 2025-09-05 Last updated: 2025-12-16Bibliographically approved

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