wind

States that porosity is the most important single parameter describing shelterbelts but is very difficult to measure or define. Describes a method for categorizing wind breaks in terms of porosity using only measured minimum leeward-wind velocity. Gives theoretical expressions for the flow through a porous shelterbelt. Describes experiment to measure wind velocities around shelterbelts of low, medium and high porosity. Shows that wind measurements could be made any height without affecting relative reduction in velocity.

Reviews current status of research in North and South America relevant to the prediction of tall building behaviour in response to wind. Four main headings are considered a)meteorological research-wind structure and climate, b) full- scale investigations of wind action on tall buildings, c) development of wind tunnel techniques for building aerodynamics, d) simplified theoretical models of wind effects on tall buildings.

Shows by comparison with simplified methods for dimensioning structural beams that the degree of tightness of a shell is not the arithmetic sum of the leakage of components. States that leakage occurs where there is a pressure difference caused by wind, temperature difference and fans. The amount of leakage depends on whether the air flow is laminar or turbulent. Gives equations for the calculation of leakage in buildings without ventilation, with natural ventilation, with mechanical evacuation and with both mechanical inlet and evacuation.

Describes the philosophy and formulation of the simple and detailed procedures for wind loading of the Canadian National Building Code of 1970. Defines design pressure in terms of the exposure of the building, its response to gusts, the mean velocity pressure and the structural shape of the building. Compares predictions of dynamic drag response and cladding pressures with full scale measurements on several tall buildings. Concludes that the predictions of drag response and windward pressure are satisfactory. Discusses area requiring further definition.

Reviews wind research prior to 1958, which was based on the simple concept of a smooth air flow resulting in static design loads for most structures. States that research for the past ten years has benefited from three innovations. These are theimplementation of a statistical theory of turbulence, experimentation with turbulent boundary layers and the collection of full-scale measurements to identify and evaluate the real wind structure.

Full scale measurements were made of wind pressures on the 177m high post office tower, London. The variation of pressure with height was studied from recordings made at nine different levels between 49m and 168m above ground level. It is suggested that wind speeds of greater magnitude than those at the top of the tower sometimes occurred at lower levels.

Analyses theoretically the natural ventilation of buildings. Derives fundamental formula for the amount of ventilation due to temperature difference from Bernouilli's theorem considering buoyancy. Explains physical meaning of friction loss and theneutral zone, derives pressure distribution due to wind from the shape of buildings and the location of openings. Obtains total expression for amount of ventilation due to both temperature difference and wind.

Ventilation rates in two test home were measured using helium as a tracer gas. Pressure differences across the exterior walls of the house were recorded using pressure taps. Gives results for air infiltration tests and the calculated air infiltration. Finds that during summer air infiltration rates varied approximately linearly with wind velocity. During the winter, the pattern and extent of air infiltration were influenced by both house stack action and furnace operation.

Reviews means of rain water penetration and how to apply one-stage weather proofing listing the disadvantages. Reviews research results obtained with two-stage weather proofing by adding an additional seal and summarises the pressure variations resulting from wind plus the design of horizontal and vertical joints between individual facade segments. Discusses the practical design of joint and sealant illustrating this for a few window types and adds that this design is also applicable for a complete curtain wall.

States heat load on buildings due to wind is dependent on the shape of building, wind direction and wind speed. Gives theoretical calculation for the heat loss due to wind based ongerman standard DIN 4701. Discusses fundamentals of fluid dynamics and the practicalities of wind tunnel tests. Recounts tests made of a block of flats in Munich. Pressure distribution due to wind was determined by a wind tunnel test on a model, giving c-profiles for different wind directions.