shielding

Investigates a rational method of utilizing recent improvements in wind tunnel techniques and meteorological data, to estimate potential wind-generated air flow through housing in hot humid climates. The method uses mean pressure differences obtained from solid wind tunnel models together with appropriate discharge coefficients for rectangular openings. Changes in pressure distributions due to typical openings through models indicated that the use of pressure data from solid models results in errors similar to those associated with the local wind data.

Reports a systematic investigation of the wind pressure variations when test models of varying height are surrounded by uniform roughness arrays of various densities in a boundary layer wind tunnel. Describes the effect of the surrounding roughness in shielding the bluff model when the model height is less than the average roughness height and of the degree of exposure experienced by a model taller than the surrounding roughness. Discusses results and gives 24 graphs of pressure coefficients.

Reports wind tunnel tests of wind velocity, RMS velocity fluctuations and energy spectra for the streamwise velocity component in the lee of model fences of permeability 0% 20%, 34% and 50%. Compares results with existing field and wind-tunnel data. Turbulence measurements define the leeward flow regions which are dominated respectively by the bleed flow and by thedisplacement flow. Gives separate empirical relationships between mean velocity and turbulence intensity for these two regions.

Describes instrumentation used to measure air flow and pressure. Presents laws for turbulent and laminar flow in a wind tunnel. Reports model experiments to investigate the flow behind a solid screen and control experiments to check the model laws. Discusses measurements made at full scale on a school and on a model of the school. Describes experiments on the shelter behind houses and the dispersal of smoke from a chimney.

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.

Reports study of the aerodynamics of wind breaks in a boundary layer wind tunnel. Describes flow patterns and shelter effects in the lee of different fences and discusses efficiency of shelters in relation to pedestrian comfort. Gives results downstream in horizontal planes by nets of isocurves showing mean speed and turbulence. Discusses the influence of permeability, shape, size and wake ventilation and suggests new designs: for example two wind breaks in series.

Reports detailed investigation of the interaction between group geometry, flow properties and resulting pressure forces on a group of buildings. 

Developes procedure for calculating air infiltration rates due to wind pressures on the exterior walls of buildings, assuming no chimney and mechanical ventilation effects. Assumes resistance to internal air flow is small. Using results of wind tunnel test, presents calculations showing the significant effects a single neighbouring building can have on the infiltration rates. Relative building heights, distance between buildings and wind direction are varied, and both uniform and shear flows are considered.

Reviews work done on the physical and biological effects of wind-breaks and shelter-belts, outlining main results. Discusses reduction in mean speed of wind, turbulence produced by shelter-belt, shading and humidity. Outlines some biological consequences of shelter-belts. Gives bibliography containing forty-seven references.

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.