How cityscapes catch the wind: predicting wind loading and natural ventilation*

Computational fluid dynamics (CFD) can inform sustainable design of buildings and cities in terms of optimizing pedestrian wind comfort, air quality, thermal comfort, energy efficiency, and resiliency to extreme wind events. An important challenge is that the accuracy of CFD results can be compromised by the large natural variability and complex physics that are characteristic of urban flow problems. This talk will discuss how this challenge can be addressed using multi-fidelity simulation frameworks with uncertainty quantification. Results will be presented for two applications: peak wind pressure load predictions, and natural ventilation in buildings in complex urban environments. For the wind loading calculations, the sensitivity of large-eddy simulation (LES) results to the turbulence in the incoming boundary layer wind is quantified and the results are validated against wind tunnel experiments. The validated LESs are then employed to gain a better understanding of the flow physics that govern small-scale extreme suction events observed in specific locations on the façade. For the natural ventilation simulations, an efficient strategy to use LESs for quantifying natural ventilation flow rates under variable weather conditions is proposed, and the results are validated against field experiments. The talk will conclude with an overview of ongoing work and open research questions for both applications.