English

Gives brief description of the new computer package developed by the Oscar Faber partnership for predicting the movement of smoke during a building fire. The model treats the building as a network and calculates air flow between rooms driven by stack effect and wind pressure. Four levels of complexity in the simulation are possible. Describes the results of these different types of analysis for a multi-storey building.

Reports measurements made of the wind pressure over a model of the Empire State Building as affected by the presence of neighboring models simulating buildings which might be erected on the adjacent blocks. Finds that while the pressure on certain faces of the building was increased somewhat by the presence of neighbouring structures, the resultant of pressure on the windward face and suction on the lee face was decreased. The decrease was greatest when the shielding structure was close by and directly upstream.

Discusses the physical nature of atmospheric boundary layer flows. Concludes that the primary aims in the simulation of these flows in a wind tunnel should b to model the relevant scales and intensities of turbulence. Simulation of the variation of mean wind velocity with height is also desirable. Proposes a system of barriers and vortex generators as a means of simulating turbulent and neutral atmospheric boundary layers.Discusses the characteristics of induced turbulent flow. Finds that the developed flow is a good approximation to the natural boundary layer.

Reports wind-tunnel measurements of wind pressure on a rectangular block. Presents results as mean isobars plotted on an exploded view of the surfaces of the model. Briefly discusses the effect of turbulence and fluctuating pressures. Concludes that mean pressure distribution is only slightly affected by turbulence and shear in the atmospheric wind.

Reports low-pressure measurements of the leakage function of a building using an alternating (AC) pressure source with variable frequency and displacement. Synchronous detection of the indoor pressure signal created by the source eliminates the noise dueto fluctuations caused by the wind. Finds good agreement between AC and DC leakage results in pressure regions where the results can be compared. The low-pressure values made with the AC source suggest that the air flow is dominated by orifice flow effects down to pressures less than one Pascal.

Presents a model for predicting air infiltration that eliminates many site- specific parameters normally required. The only information necessary is the geometry and leakage of the structure obtained from fan pressurization measurements. Theleakage quantities, expressed in terms of effective areas, are total leakage area and the leakage areas of the floor and ceiling. Weather parameters are mean wind speed, terrain class, and average temperature difference. The model separates the infiltration problem into two distinct parts: stack and wind regimes.

Reports an investigation of wind loading with emphasis on the local pressure fluctuations, on a small scale building model in a thick turbulent boundary layer wind tunnel. A striking similarity between the oncoming turbulent energy spectra andsurface pressure-fluctuation spectra was consistently observed. This similar behaviour suggests that the upstream turbulence plays a dominant role in producing the pressure fluctuations on the upwind face of a bluff body.

Describes technique for measuring the volume of air leaving a house through the loft. Two tracer gases are used; nitrous oxide is released in the house and carbon dioxide in the loft. The mean concentration of N2O in the loft gives the volume of house air infiltrating the loft: and the mean concentration of CO2 gives the ventilation rate of the loft itself.< Gives two examples of the use of this technique and gives loft ventilation rate as a function of wind speed for one house.

Outlines two techniques for estimating ventilation heat losses in houses. The first is a tracer gas technique using a constant concentration of gas and the second a theoretical prediction method. The theoretical technique treats the building as a multi-cell model with specified wind pressure, leakage openings and background leakage area. Reports use of the method for simulating the natural ventilation of a house in London and the effectiveness of sealing the windows and floor.

Reports experiments carried out in a wind tunnel on two kinds of two-dimensional roughness arrays and on one array of three-dimensional roughness with a turbulent boundary layer growing over the arrays. Drag coefficient on an individual element was measured by pressure tapping as its height was varied relative to the average height of the array. Some general forms for the drag coefficients are found for the two-dimensional case. Results for the three dimensional case show some general trends but more work is needed.