575 publications from this institution
Climate observations and analyses by the Intergovernmental Panel on Climate Change and national meteorological organizations show that climate change is occurring. This chapter discusses the simulation of urban thermal microclimate with a focus on heat waves in urban areas, the simulation of overheating of buildings and the effects of adaptation measures to limit temperatures in buildings and urban areas during heat waves. In order to assess heat waves, urban heat islands and climate change adaptation measures for urban areas, different simulation tools can be employed. The spatial scales are the meteorological microscale and the building scale; the methods are computational fluid dynamics and building energy simulation. Adaptation measures investigated at the neighborhood scale are avenue trees, green facades and green roofs; adaptation measures at the building scale are increased thermal resistance, increased thermal mass, increased short-wave reflectivity of facades and roofs, peak ventilation, vegetated roofs and exterior solar shading.
Turbulence modeling is a key issue in computational wind engineering, particularly in the prediction of pollutant dispersion in cities. To be directly applicable, turbulence models need validation by comparison with experiments. This paper evaluates the performance of two different modeling approaches (RANS k-e and LES) for three test cases with varying complexity. For each case, wind tunnel experiments are used for validation. It is shown that the performance of the standard k-e model is very case-dependent and that it also depends on the turbulent Schmidt number, whose optimum value is a priori unknown. On the contrary, LES with the dynamic subgrid-scale model shows a good performance for all cases, without requiring any parameter input to solve the dispersion equation. For the test case of an actual urban environment, predicted concentration values with LES differ from experiments by less than a factor of 2, compared to less than a factor of 4 with the standard k-e model.
