CFD Analysis to evaluate the different microclimate parameters within an area of Politecnico di Milano

The simulation of urban microclimates to assess their impact onto the energy needs of buildings and on the outdoor thermal comfort is the focus of an increasing number of contributions in the Literature, with intertwined contributions from microclimatology, urban studies, and building physics. In particular, the wind velocity field within the urban canopy, namely below the average height of buildings, crucially influences the thermal conditions in the urban fabric. In facts, the urban canyon effect yields to air temperatures by 2-3°C higher within than over the canopy. The wind velocity, depending on the urban geometry, is also reduced within the canopy, even to the 30% of the value measured above the rooftops. Herein the results of a thermo-fluid dynamic analysis are presented relating to the velocity field and the microclimate in the boundary layer of a complex of buildings within the Campus of Politecnico di Milano. The simulations were performed with a CFD RANS software model (Fluent ANSYS release 14) with the k- ε turbulence scheme. The results of the simulations were compared to local sonic tri-axial anemometry and air temperature within the canopy, and with bi-axial sonic anemometry data over the canopy. The global solar radiation and air temperature over the canopy were also used to control the boundary conditions defined for the simulation. The modelled profiles show good agreement with the measurements within and over the canopy. The software model was then used to assess possible options to improve the building energy needs within the studied domain.