The effect of 3D geometry complexity on simulating radiative, conductive and convective fluxes in an urban canyon

Abstract

The Geomatics Synthesis Project (GSP) was an eight-week culminating group project by seven second-year MSc. Geomatics students. The objective was to undertake group and fieldwork through a real-world project with an external organization. In association with Laboratoire des Sciences de L'Image Informatique et Teledetection (LSIIT) at the University of Strasbourg, the 2012 GSP explored the impact of 3D geometry complexity on the accuracy of simulating radiative, convective and conductive fluxes in an urban canyon. The research involved the collection of meteorological data near the urban canyon in Strasbourg, France, for input into a model called LAtent, SEnsible, Radiation Fluxes (LASER/F), which simulates the aforementioned fluxes. The preparation of seven geometry scenarios with different complexities was completed and test run in LASER/F. The results were validated with thermal images of two facades collected during the field campaign in Strasbourg. The results show that LASER/F systematically underestimates facade surface temperatures due to various model assumptions. One of those is the oversimplified 1D parametrization of the wind and was demonstrated by comparing it with a vertical wind profile extracted from a Computational Fluid Dynamics (CFD) model. Nevertheless, it was concluded that the most complex 3D geometry does not necessarily improve simulation accuracy, especially during warming periods of the day. The inclusion of balconies on the facades is influential and should be used for future simulation experiments when it is a signifcant feature of the facade. Further research is required to better understand canyon geometry effects such as canyon orientation, aspect ratio and the volumetric influence on internal heat storage in buildings.