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Abstract.A comparison between numerical simulations and wind tunnel modelling has been performed to examine the variation with streamwise aspect ratio (width/height, W/H) of the mean flow patterns in a street canyon. For this purpose a two-dimensional (2-D) cavity was subjected to a thick turbulent boundary layer flow perpendicular to its principal axis. Five different test cases, W/H = 0.3, 0.5, 0.7, 1.0 and 2.0, have been studied experimentally with flow measurements taken using pulsedwire anemometry. The results show that the skimming flow regime, with a large vortex in the canyon, occurred for all the cases investigated. For the cavities with W/H≤0.7 a weaker secondary circulation developed beneath the main vortex. The narrower the canyon, the smaller the wind speed close to the cavity ground, giving increasingly poor ventilation qualities. The corresponding numerical results were obtained with the Computational Fluid Dynamics (CFD) code CHENSI that uses the standard k-ε model. The intercomparison showed good agreement in terms of the gross features of the mean flow for all the geometries examined, although some detailed differences were observed.

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SUMMARYNatural convection around the human head 1. Factors determining the convective flow patterns around the human head in 'still' conditions are discussed in relation to body posture.2. These flow patterns have been visualized using a schlieren optical system which reveals that the head has a thicker 'insulating' layer of convecting air in the erect posture than in the supine position.3. Local convective and radiative heat transfer measurements from the head have been made using surface calorimeters. These results are seen to be closely related to the thickness of the convective boundary layer flows.4. The total convective and radiative heat loss from the head of a subject in the erect and supine position has been evaluated from the local measurements. For the head of the supine subject the heat loss was found to be 30% more than when the subject was standing.