Preprints
https://doi.org/10.5194/egusphere-2024-96
https://doi.org/10.5194/egusphere-2024-96
20 Feb 2024
 | 20 Feb 2024
Status: this preprint is open for discussion.

A conservative immersed boundary method for the multi-physics urban large-eddy simulation model uDALES v2.0

Sam Oliver Owens, Dipanjan Majumdar, Christopher Edward Wilson, Paul Bartholomew, and Maarten van Reeuwijk

Abstract. uDALES is an open-source multi-physics microscale urban modelling framework, capable of performing large-eddy simulation (LES) of urban airflow, heat transfer, and pollutant dispersion. We present uDALES v2.0, which has two main new features: 1) an improved parallelisation that prepares the codebase for conducting exascale simulations; and 2) a conservative immersed boundary method (IBM) suitable for an urban surface that does not need to be aligned with the underlying Cartesian grid. The urban geometry and local topography are incorporated via a triangulated surface with a resolution that is independent of the fluid grid. The IBM developed here includes the use of wall functions to apply surface fluxes, and the exchange of heat and moisture between the surface and the air is conservative by construction. We perform a number of validation simulations, ranging from neutral, coupled internal-external flows and non-neutral cases. Good agreement is observed, both in cases in which the buildings are aligned with the Cartesian grid and when they are at an angle. We introduce a validation case specifically for urban applications, for which we show that supporting non grid-aligned geometries is crucial when solving surface energy balances, with errors of up to 20 % associated with using a previous version of uDALES.

Sam Oliver Owens, Dipanjan Majumdar, Christopher Edward Wilson, Paul Bartholomew, and Maarten van Reeuwijk

Status: open (until 04 May 2024)

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  • RC1: 'Comment on egusphere-2024-96', Anonymous Referee #1, 30 Mar 2024 reply
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Sam Oliver Owens, Dipanjan Majumdar, Christopher Edward Wilson, Paul Bartholomew, and Maarten van Reeuwijk
Sam Oliver Owens, Dipanjan Majumdar, Christopher Edward Wilson, Paul Bartholomew, and Maarten van Reeuwijk

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Short summary
Designing cities that are resilient, sustainable, and beneficial to health requires an understanding of urban climate and air quality. This article presents an upgrade to the multi-physics numerical framework uDALES, which can model microscale airflow, heat transfer and pollutant dispersion in urban environments. This upgrade enables it to resolve realistic urban geometries more accurately, and to take advantage of the resources available on current and future high-performance computing systems.