Simulation and Validation of CFD turbulent airflow at pedestrian level using 3D ultrasonic anemometer in the controlled urban area “Sense-City”

Abstract

Computational Fluid Dynamics (CFD) is increasingly used to describe the airflow in urban environments. In this study, we aim to simulate and to validate the airflow in a full-scale urban area submitted to controlled climatic conditions through an impressive climatic chamber. This non-standard equipment named “Sense-City” is made up of a 400 m2 realistic district with buildings and street layout. The Sense-City urban area is highly instrumented, which allows notably the validation of physical models and simulations and the test of innovative urban solutions. Using a URANS model, with the k-omega SST model as the closure model, a CFD analysis is made on the turbulent airflow in Sense-City at a reasonable computational cost. The simulated velocities and turbulent kinetic energy are compared with measurements collected at a pedestrian level using a 3D ultrasonic anemometer. We show that the numerical simulations correctly predict the flow direction and flow characteristics such as regions of near-zero velocity. Geometry simplifications, uncertainties on the boundary conditions and the use of a coarse mesh and time discretization to fulfill operational purposes have led to a Root Mean Square Error (RMSE) score of 0.26 m/s on the velocity magnitude.