Showing papers by "Rex Britter published in 2005"

Summertime urban heat island hysteresis lag complexity

Abstract: At a time when the world is rapidly urbanising, civil and environmental engineers, urban planners and policy makers around the globe are faced with the complex issues of how to design and construct urban regions to be sustainable. During this time of unprecedented growth, environmental engineers and scientists are faced with the additional complexities of global and regional climate change. This review paper focuses on the nexus of rapid urbanisation and summertime local climate change that can be addressed at the regional level—the built environment. First, it assesses the volumetric and physical characteristics that comprise the urban fabric of a region. Second, the paper presents a review of research efforts to date to quantify how surface material applications and microclimate are subject to the laws of thermodynamics, which can be altered in terms of engineered alternatives. This includes a review of surface mitigation research as presented in the context of sustainability.

A Simple Model for the Movement of Fire Smoke in a Confined Tunnel

Abstract: Fires in tunnels are unfortunately frequent occurrences often with tragic outcomes. A recent example is the fire on the funicular train at the ski resort in Kaprun (Austria), which caused nearly 160 deaths. Design engineers and risk analysts require knowledge of the fluid dynamics of the fire and smoke movement to answer questions such as how much oxygen can access and feed the fire, and what concentration of smoke will the people be exposed to. As an example in the Austrian accident the geometry was a long tunnel with fire doors closed at one end, and with a fire initiated near the closed (lower) end. The hot smoke from the fire is a source of buoyancy; the smoke reaches the ceiling of the tunnel, and then develops along the ceiling as a wall-bounded plume. The motion of the smoke is driven by a buoyancy force, but at the same time, mechanisms of turbulent heat and mass transfer act as a brake to this motion. In this paper we present how a generic model describing a semi-enclosed buoyancy-driven flow can be interpreted and used in the modelling of fire smoke movement in a confined tunnel. A consideration of the net pollutant volume flux through the tunnel leads to predictions for the variation of concentrations along the tunnel. The smoke concentrations near the fire smoke source scale linearly with the length of the tunnel, with higher concentrations at the lower section of the tunnel, as could be expected. Similarly the concentration of oxygen making its way through to the fire source decreases linearly with the length of the tunnel. A lower bound estimate of the smoke residence time can be obtained based on smoke concentration predictions from the model.

Numerical model inter-comparison for a single block building within ATREUS

Abstract: Page 302 NUMERICAL MODEL INTER-COMPARISON FOR A SINGLE BLOCK BUILDING WITHIN ATREUS S. Vardoulakis, R. Dimitrova, K. Richards, D. Hamlyn, G. Camilleri, M. Weeks, J-F. Sini, R. Britter, C. Borrego, M. Schatzmann, N. Moussiopoulos Department of Environment & Planning, University of Aveiro, Portugal. Current afiliation: School of Geography, Earth & Environmental Sciences, University of Birmingham, U.K. Laboratoire de Mecanique des Fluides, Ecole Centrale de Nantes, France. Meteorological Institute, University of Hamburg, Germany. Department of Engineering, University of Cambridge, U.K. Laboratory of Heat Transfer & Environmental Engineering, Aristotle University of Thessaloniki, Greece.

techniques: winds and dispersion

Abstract: Summary The focus is the analysis of urban Digital Elevation Models (DEMs) with image processing techniques. A brief review of existing methods to derive sky view factors, building energy consumption and space syntax shows how well established parameters that relate to airflow and dispersion (such as the height-to-width of urban canyons and the aerodynamic roughness length) can be calculated. Other measures of urban directionality and periodicity, inspired by traditional image processing, are also introduced, such as the Radon, Hough and Fourier transforms and the variance plot. Analyses of three case study sites in London, Toulouse and Berlin are compared, showing considerable variation in the chosen parameters. Results suggest that the DEM format is an extremely versatile tool to investigate the urban intermediate scale, allowing analyses that would be very difficult or impossible to carry out using traditional vectorial models.