LES modelling of unsteady flow around the Silsoe cube

Large Eddy Simulation is used to model the unsteady flow over the Silsoe 6 m cube with the wind perpendicular to one face. The mean, standard deviation, maximum and minimum pressure coefficients are shown to be in reasonable agreement with published data. In regions affected by building induced pressure fluctuations the standard deviation coefficient is higher than in full-scale due to the lower turbulence intensity in the LES model. Conditional averaging is used to highlight the sequence of pressure changes that occur around strong suction spikes on both the sidewalls and roof. The LES model is shown to reproduce the pattern observed in full-scale. Flow visualisations reveal that these events are associated with the formation of a strong vortex on the windward half of the sides or roof, which is then shed and carried downstream.