The Welsh School of Architecture's wind tunnel facility is used to investigate the wind induced environment around buildings. It is available for use in research, student projects, consultancy and collaborations.
This is a boundary layer wind tunnel, it essentially produces a scale model of the variation of wind speed and turbulence with height found in real winds.
The wind tunnel was built in the early 1970's, and originally sited at and used by British Gas Watson House Research Station in London. The wind tunnel was donated by British Gas to the Welsh School of Architecture in 1993.
The wind tunnel provides a working cross section of 2m by 1m height, the total length is 12m. The bellmouth entry area is 2.6x5.2m
A 6m upstream fetch uses a combination of blockages, fences and surface roughness (Lego Duplo blocks) to produce a simulation of the lower part of the atmospheric boundary layer. The working section at the back of the tunnel is 2m length; a model is placed on a 1.9m maximum diameter baseboard in that zone.
The tunnel is powered by two 13hp fans, providing a maximum speed of approximately 11m/s.
Instrumentation for the wind tunnel includes:
- Dantec hot-wire anemometry equipment
- Dantec laser doppler anemometry equipment
- Furness low pressure transducers with Scanivalve scanners
- various video cameras, recorders and image capture equipment
In the design of natural ventilation systems or strategies for buildings, it can be insufficient to consider only the effects of buoyancy, the "stack-effect". The action of the wind may not always provide beneficial forces or flows, and can in some cases conflict with or even negate the stack-effect forces.
The detailed design, prediction, or assessment of natural ventilation strategies therfore requires a knowledge of the air pressures generated by wind effects at the openings of the building envelope. These pressures are often dictated by the form of the building itself, as well as by its surroundings. Scale model testing in a boundary layer wind tunnel continues to provide a viable method to produce this knowledge.
Wind tunnel testing allows the driving pressures to be assessed and measured, taking full account of the effects of the buildings' form and of the buildings' surroundings.
A model is instrumented by bringing multiple surface pressure taps out to scanning pressure sensors using fine tubing, as in the above illustration. Mean surface pressures measured in the wind tunnel, related to the free stream pressure potential, provide pressure coefficients Cp, which can be used to determine full scale surface pressures for a given site wind speed and direction.
Street Level Wind Environment
High wind speeds and gusts at ground level can produce unpleasant and potentially unsafe areas for pedestrians. The interaction of a buildings' form and its' surroundings can lead to areas of calm or of gusty wind conditions. The modification of the natural wind flows caused by buildings or groups of buildings can be unexpected. Wind tunnel testing provides a method for the identification and assessment of wind flow patterns around, and through, buildings and their features.
The wind tunnel data can easily be displayed in the form of contours of wind amplification. In this, red areas highlight zones of relatively high wind speeds and ground level, while green areas denote zones of relative calm.