Spires and roughness elements upstream of the model are used to create a realistic simulation of a full-scale ABL flow, both in terms of velocity and turbulence. The latter is important if gusts are to be modelled accurately.
Two sets of instruments are used in the tunnel, each mimicking the apparatus used for the full-scale tests. A Cobra probe is fitted to the model Muirhead Tower. This measures the wind velocity 200 times per second, and provides a reference velocity which allows the physical simulation results to be mapped onto the full-scale data. Irwin probes are the industry standard for this type of pedestrian level study, and are fitted along the line of the full-scale test route. Future work will use hot-wire probes to further investigate the flow field.