Sets out the similarity requirements which must be observed so that results of wind tunnel tests may be used to predict behaviour of full-scale prototypes in the natural wind. Discusses rigid models, suspension bridges, models of slender towers. Outlines problems of representing natural wind and the effect of wind tunnel-wall interference. Introduces correction procedure for wake blockage which permits the use of larger wind-tunnel models than would otherwise be possible without serious errors.
Discusses use of long boundary layer wind tunnel to produce a more realistic model of natural wind than that obtained in conventional aeronautical wind tunnel. Reports tests made tofind wind velocity profile and model tests to find dynamic response to wind loads and local pressures on buildings. Finds aeroelastic model response in turbulent flow is markedly different from that in smooth uniform velocity. Concludes that adequate simulation of natural wind has been obtained. Finds comparison between model and full-scale tests is encouraging.
Describes experimental techniques used to produce turbulent boundary layers in a wind tunnel. Gives model law for velocity profile in a turbulent flow over a rough surface. Describes wind tunnel, five tunnel coatings used to generate turbulence, themodels and instrumentation. Gives as an example the test results from a model of house with desk roof.
Describes method of estimating roughness required to generate velocity profile of a given shape with a boundary layer of agiven depth. Uses data correlation for the wall stress associated with very rough boundaries and a semi-empirical calculation method to calculate the shape of boundary layers in exact equilibrium with the roughness beneath them. Results can be summarized in a single figure which relates shape factor of boundary layer to height of roughness elements and their spacing
Describes a photo-electric technique for instant determination of contaminant concentration in wind tunnel studies of stack gas dispersion. A roving sensor is used to measure the light scattered by the particles of oily aerosol representing theprototype stack effluent. The minature probe has a noise level of only one hundred thousandth of the full linear range of the output signal for a time constant of 5s. Device is also suitablefor measurement of fluctuating flow properties, such as turbulence, where a high frequency response is required.
Reports wind tunnel investigation of the wind pressure on houses. Tests were made on model of traditional form with sides in the ratio 1:3 and 1:6, roof pitch of 14 and heights of 2,3,4 and 8 storeys. Results were obtained in the form of pressure coefficients which are transformed into isobars using spline interpolation. Gives diagrams showing pressure coefficients and isobars for each test.
Reports wind measurements made on a multi-storey building. Gives contours of overall pressure coefficients and wind velocity profiles. Compares results with series of wind-tunnel model tests and finds full-scale measurements were quite different from model tests. In an attempt to gain greater physical insight into the problem tests were made on a two-dimensional bluffplate immersed in a turbulent boundary layer. Finds correlation of drag coefficient with boundary layer parameters for quasi-equilibrium type layers.
Presents measurements of the mean and fluctuating pressure field acting on two-dimensional square cylinder in uniform and turbulent flows. Shows the addition of turbulence to the flow raises the base pressure and reduces thedrag of the body. Suggests this is attributable to the manner in which increased turbulence intensity thickens the shear layers, which causes them tobe deflected by the downstream corners of the body and results in the downstream movement of the vortex formation region.
Discusses pressure distribution on buildings. Describes wind tunnel tests on model buildings. Pressure distribution on walls were measured in a constant velocity field and in anartificially produced velocity gradient. Discusses results and deduces rules by which pressure distribution and wind loads can be predicted for buildings in any specified wind field. Changes in the flow pattern due to the velocity distribution were observed and correlated with the pressure distribution.
Due to the complicated flow phenomenon in urban areas, the assessment of wind pressure forces as well as the rates of natural ventilation for groups of low rise buildings is complex. As a result, the current design methods for the prediction of these forces are oversimplified and lead to inaccurate estimates of wind forces and ventilation rates in buildings. A survey of previous studies regarding wind properties and their influence on pressure forces along with work related to natural ventilation, wind loading and air flow round buildings was carried out.
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