Microscale obstacle resolving air quality model evaluation with the Michelstadt case

Area of Science:

• Environmental Science
• Fluid Dynamics
• Atmospheric Chemistry

Background:

• Urban obstacles significantly impact air flow and pollutant dispersion, posing challenges for traditional air quality models.
• Computational Fluid Dynamics (CFD) models offer a potential solution by resolving urban canopy flow fields and explicitly accounting for building effects on dispersion.

Purpose of the Study:

• To evaluate the performance of an open-source CFD code, OpenFOAM, for modelling pollutant dispersion in a complex urban geometry.
• To assess the reliability of CFD models for regulatory use in intricate urban environments.

Main Methods:

• Utilized OpenFOAM, a general-purpose CFD code, to simulate pollutant dispersion in the Michelstadt urban geometry.
• Employed a scalar transport equation alongside CFD to model dispersion, considering building effects.
• Performed verification and validation against available flow field and dispersion measurement data.

Main Results:

• The study analyzed continuous release dispersion results, highlighting the strengths and weaknesses of the CFD modelling approach.
• The turbulent Schmidt number was identified as a critical parameter, with a value of 0.7 providing the best statistical metric results.
• OpenFOAM demonstrated capability in simulating dispersion within a complex urban setting.

Conclusions:

• CFD models, specifically OpenFOAM, show promise for simulating pollutant dispersion in complex urban geometries.
• Rigorous verification and validation are essential for building confidence in CFD models for regulatory applications.
• Optimizing parameters like the turbulent Schmidt number is crucial for enhancing the accuracy of urban air quality predictions.