turbulence

Considers the rise in air pressure inside a closed building with openings on the windward side, caused by gusts of wind and the increased pressure on the building envelope, especially on the roof. Derives expressions for the transient pressure inside the building, dependent on the velocity of the wind, the volume of the building and the size of openings on the windward side. Notes that in general buildings are more permeable than has been assumed

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.

Discusses problem of assessing wind loads on buildings. Describes general properties of the wind and suggests wind can be described by its mean velocity with superimposed gusts. Suggests averaging period of 10-15 minutes for the mean velocity. Gives empirical expression for wind spectra. Considers relationship between extreme value of wind speed and the parent distribution. Suggests influence of gusts is not best determined by maximum gust speeds. Finds mean wind speed profile and turbulent structure are strongly dependent on terrain.

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.

Reviews some previous work on the measurement of wind pressures at full-scale. Deals with some of the problems arising. Describes pilot investigation being made at State House, Holborn to develop suitable techniques and to study the effect of gusts on pressure distribution. Gives preliminary results and mentions problem of establishing a suitable reference pressure.

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 measurement of wind pressures on Royex House, a multi-storey building in London. Reports that suction loads on cladding are more severe than had been indicated by wind tunnel tests. Face-on winds produce the maximum structural loading with whole of peak load on windward face.

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.