Seite - 82 - in Intelligent Environments 2019 - Workshop Proceedings of the 15th International Conference on Intelligent Environments

model that uses an input file for heat flux in its boundary conditions. This type of numerical methods is called static or one way coupling. Another mathematical model was then used to calculate thermal stratification. In this case the CFD RANS code was implemented with a full energy balance scheme taken from the model described in chapter two. This type of modelling is called dynamic or two way coupling. Air temperature differences were obtained after subtracting the results of the dynamic method from the static method. The sub-domain containing four buildings at the centre of the numerical domain was taken exclusively into account for the comparative study. This strategy was chosen due to calculation errors that might appear near the boundaries of the calculated domain. Results from hours 05.00, 10.00, 12.00, 15.00 and 20.00 were taken into account. Time steps were set for five minutes each. The domain size is 108 metres x 108 metres x 54 metres. The grid resolution is set at 1 metre x 1 metre x 1 metre. It includes 16 three-floors residential buildings made from concrete. Every single building has a footprint of 81 square metres. Weather data for August 11 th 2013 has been obtained from AMEDAS. This day represents the hottest day registered over 2013 in central Tokyo. Temperatures exceeded 37°C. The initial boundary conditions for the vertical profiles of wind, potential temperature, humidity, pressure, kinetic energy, dissipation rate of the kinetic energy and wet and dry air molecules were created so as to initiate calculations by considering both the weather data discussed above and the grid’s height. Wind speeds and radiation were important meteorological factors for this study. Figure 4. It shows air temperature differences after subtracting the results of the dynamic method from the static method in xy, xz, and yz sections that were calculated for z=10 metres, y=54 metres and x=54 metres respectively at hour 10.00. The flow up wind was blowing westerly at 0.9 m/s with a radiation amount of 2.47 MJ/m 2 . Air temperature differences between the two models were significant. The significant amount of radiation and lower wind speeds allowed the dynamic model to calculate a clearer and significant convective flow. Static coupling overestimates air temperatures near surface and on the top of buildings. It underestimates air temperatures inside the canyon and above it (the open space) at 10.00. This might be M.Bakkali andY.Ashie /RANSModelling forLocalClimates,EnergyUseandComfortPredictions82