Numerical Simulations of Thermal Effects of Building Walls

Coupling a mesoscale numerical model with computational fluid dynamics (CFD) capabilities enabled us to simulate the air flows around and inside of buildings under the influence of local circulations such as sea- and land-breezes. Buildings block and redistribute air flows in urban areas. Buildings also contribute to urban heat islands due to heating and cooling of building walls and roofs. However, field observation data were limited and including every details of building morphology in the model was difficult. Consequently, verification of model results encountered considerable uncertainties.

Alternatively, the model results may be compared with wind tunnel data. The Central Institute of Electric Power Industry (CRIEPI) in Japan conducted a series of wind tunnel experiments where model building walls were heated. Numerical simulations were conducted to simulate the air flows around blocks (H x D x W = 12 cm x 12 cm x 72 cm) in the wind tunnel. Either windward or leeward wall of a block was heated to 170 ºC while the air temperature was 20 ºC. The wind speed was 0.65 m/s which resulted in the bulk Richardson number of 1.42. The present numerical model was based on the ensemble averaged second-moment turbulence-closure equations. The model results were compared with the wind tunnel data and LES model simulations conducted at CRIEPI.