Invited response and open forum discussion

Abstract

The problems had some similarity in the techniques which could be used to solve them but there may be a need to develop new techniques for flow modelling and verification of proposed solutions. The first problem related to the roof of a stadium and typified the developing situation where an increasing number of lightweight structures is being designed with little basic knowledge available in Codes or Data Items and where windtunnel techniques do not appear to be well established. The second problem involved the assessment of pressures over a glass-clad building of unusual and irregular shape which would be difficult to model and the accuracy and adequacy of the predicted data was challenged. Having defined these two problems Dr. Wootton asked Prof. Nick Cook to outline the advice he would give to clients. Prof. Cook began by reminding us of the need for information on (i) the wind climate at the site, (ii) the distribution of flow properties within the boundary layer, and (iii) the structure to be tested. Since the latter two items interacted with one another, he preferred to test a model in a windtunnel with suitable boundary layer simulation rather than CFD modelling of these problems. Wind climate at the particular site could be estimated by use of Meteorological Office data from nearby locations, corrected for changes of ground roughness, etc., for the various upwind directions at each location to define a standardised site climate. Ext~'eme wind speeds, mean wind speed and direction frequencies and wind profile parameters for various directions of wind and the associated ground roughness could then be estimated for the specific site. These profile parameters would then be modelled in a windtunnel and spectra scales, etc., matched with a model of the site,