wind

The second of two sections of a report of air change measurements in the winter period 1975/76 of non-air conditioned buildings in Switzerland, chiefly dwellings. Recapitulates the reasons for the research, the theoretical bases, measurement method used and aims of the experimental investigations. Sets outin tables detailed results of measurements carried out in a wide range of Swiss dwellings of different ages, locations, construction, design and type.

This parameter study with the IMG calculation model for ventilation is an attempt at forming some background for decisions relating to the preparation of a standard in the Netherlands. From the results one can see that air tightness and the heat loss caused by infiltration cannot be considered as a simple linear relationship .

The method to calculate flow processes in multi-storey buildings having uniform storey arrangement(residential and office buildings) can be simplified to an extent enabling calculation by hand. Nomographs are given to calculate flows in sectional and central corridor buildings. The air flow rates depending on the action of wind, buoyancy and exhaust air plant operation can be derived from these nomographs for different combinations of flow resistances of the buildings. The latter factors may be included in thecalculation either individually or in any combination.

Reports an investigation of the effects of temperature differences, pressures, sun and wind conditions on a thermal image produced by thermography. This investigation is concerned mainly with measurement points associated with air leakage. Reports measurements on a single-storey timber-framed house under a pressure difference of 5,-2,-10 and -20 Pa.

Considers the characteristics of flow through small gaps. Discusses relation between wind tunnel measurements and actual wind pressure on buildings and the effect of building shape on ventilation. Derives equations for flow rate through a gap for different temperature and pressure differences and sizes of gap. The equations consider the pressure as a function of time thus modelling the effects of a turbulent wind incident on a gap.

Contains two papers reprinted from the Jnl. of Ind. Aerodynamics:-< 1) Wind-tunnel simulation of the adiabatic atmospheric boundary layer by roughess, barrier and mixing-device methods.< Discusses the philosophy of roughness, barrier and mixing-device simulation methods. Illustrates methods by measurements of simulations in the B.R.E.boundary layer wind tunnel.

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.

Treats importance of keeping uncontrolled ventilation to a minimum in buildings equipped with balanced ventilation. Provides theoretical and experimental description of leakage of air past windows. Includes comparison between standards of different countries. Discusses effect on building ventilation of variations of wind and outdoor temperature. Considers in conclusion measurement of air flows between rooms in a building. Describes development of tracer gas method based on computer-assisted evaluation.

Discusses the effect of wind on air change rates in buildings. Reports series of model tests conducted in a water flume and a wind tunnel. A plexiglass box with holes in it was filled with gas, either nitrogen or carbon dioxide, and placed in a controlled air flow. The concentration of gas was plotted in a semi-logarithmic form. Gives typical examples of these graphs.Discusses feasibilty of estimating rate of air change by a hyperbolic function, but finds that more tests are needed forpractical recommendations.

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.