wind tunnel

Discusses conditions that must be satisfied for a model in a wind-tunnel to give the same air-flow as a full-sized building. Reports two series of tests on interior and exterior air flow patterns, made on a full-sized building and a scale model of the building. Air flow patterns were observed using titanium tetrachloride smoke. Tests were also made to determine the limits by which the product of the height of the model by the air speed may vary without serious error.

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.

Gives a brief account of exploratory efforts to isolate the contributions of flow separation and reattachment to local surface pressure fluctuations. The study is restricted to tall buildings with sharp vertical edges. Pressure fluctuation measurements were made on small scale models of actual buildings placed in uniform flow of low turbulence level. Gives figures showing mean and root-mean-square pressure coefficients. Finds maximum instantaneous pressure fluctuation was four times the root-mean-square value. Describes characteristics of pressure fluctuations.

Reports measurements of wind pressure distributions on the surface of a rectangular cylinder model in a wind tunnel. Finds fluctuating character of pressure on roof surface is dependent on the turbulent structure of wind tunnel flow. Experiments were also made on box-shaped models with square section. Finds windpressure distribution on the roof became uniform with increasing height of the model. Gives diagrams of wind pressure coefficients.

Reports measurements of pressure distribution on square cylindrical models in wind tunnel. Vertical distribution of wind velocity was produced by grids of horizontal rods at varying spacing. Wind pressure distributions on model-scale buildings were obtained, varying the height, width, depth and winddirection. To compare results, a large-scale model 3.6 metreshigh 1.2 metres by 1.2 metres in plan was placed on the shore and pressure distribution measured during a strong wind. Gives diagrams of pressure distributions.

Describes a probe, developed for sensing static pressure in two-dimensional air flow. It was designed as a sensor for the measurement of static pressure acting on the surface of a building but the design also permits it to be used in free-stream flow. Gives details of the construction of the probe, calibration procedure and the effects of Reynolds number and of the sensitivity of the probe to pitch.

Describes tests made to find wind pressure on models in a low-velocity wind tunnel. Three basic forms:- a semi-cylinder, a rectangular vertical wall and a block-type gabled building were tested at several different angles to the wind. Gives typical pressure patterns for block-type model. Suggests use of average pressure coefficient for calculation of wind loads determined from pressure distribution. A short series of tests on the effect of shielding building showed that negative pressure on some walls could be increased by an adjacent building.

Detailed sets of time-averaged surface pressure coefficients were recorded over the walls and roof of a rectangular building model, set in a simulated high density urban area. The 1/400 scale model represented a generalized smooth surfaced building of 100x150 ft plan form, whose height varied from 300 ft to 200,100 and 50ft. Surrounding roughness elements equalled the heightof the 50ft, building model. Tests were carried out at twelve wind angles using a power low velocity profile with an exponent of 0.43.

Reports model scale experiments to investigate the validity of digital analogue methods of predicting natural ventilation. Finds calculated ventilation rates up to 30% higher than observed model ventilation rates. Shows differences between observed and computed results caused by operating efficiency of ventilation openings being less than calibrated efficiencies. Corrected ventilation rates, allowing for changes in efficiency due to pressure fluctuations and lateral air flows over model surfaces showed close agreement with observed results.

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.