Seite - 83 - in Intelligent Environments 2019 - Workshop Proceedings of the 15th International Conference on Intelligent Environments

related to shading and/or wind flow. There is a tendency about the ‘one’ way coupling which consists in overestimating surface temperatures that obviously affects air temperatures near surface on the ground and on the top of buildings. However, air temperatures are underestimated within the gap surrounding buildings or canyons through this approach. Surface temperature is overestimated and air temperature is underestimated. Figure 5. 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 12.00. The flow up wind was blowing south-south easterly at 3.2 m/s with a radiation amount of 2.60 MJ/m 2 . Air temperature differences between the two models were less important than the calculated differences at 10.00, although the quantity of radiation inputted was higher. The reason could be that a higher wind speed generated additional turbulence, i.e. wind shear that removed heat. Static coupling overestimates air temperatures near the surface, on the ground and between the buildings inside the street canyons in parallel to the main flow at 12.00. In general, major air temperature differences were regularly calculated near surface on the ground and around the buildings. The static approach calculated the highest values in these locations. This could be explained through the fact that surface temperatures used in the static coupling were especially higher for pick temperatures and this affected air temperatures near surface. The same numerical method underestimated air temperatures over the canopy, which showed that the fact the model overestimated surface temperatures it also underestimated air temperatures in order to maintain the energy balance especially within the sensible heat flux term assumed via the product of an averaged convective heat transfer coefficient and the difference between surface and air temperatures. The dynamic method in contrast underestimated surface temperatures and overestimated air temperatures with similar considerations of the energy balance. This is why air temperatures near surface were lower and they were higher over the canopy. In this model, the variations and amplitudes of air temperatures are more important except near surface. This variability is due to both wind shear and buoyancy. M.Bakkali andY.Ashie /RANSModelling forLocalClimates,EnergyUseandComfortPredictions 83