Towards quantitative visualisation of transient surface flow on building models using infrared thermography

This paper describes a feasibility study on improving the spatial and the temporal resolution of the visual technique proposed in 1996 by Yamada, Uematsu and Sasaki and applying it to the flow over the surfaces of model buildings. A cube with 100 mm sides was constructed of aluminium sheet, mounted on a ground plane and immersed in smooth uniform flow at around 10 m/s. The internal temperature of the cube was maintained at 50°C by constantly circulating hot water through it. The surface of the cube was coated with a uniform layer of a number of insulating materials, in turn, and the temperature of the outer insulated surface was monitored using an infrared camera. A 1.5-mm-thick neoprene sheet gave a range of surface temperature around 16°C and a time constant of about 3 s. A 0.23-mm-thick PVC sheet gave a range of around 4°C and a time constant of about 1 s. Self-adhesive PVC “Gaffer tape” of around 0.1 mm thickness gave a range of around 2°C and a time constant of about 0.2 s. In this last case, unsteady fluctuations of the surface flow were clearly visible. The patterns observed were very similar to patterns of surface flow and surface pressure in published literature.