On dynamics of the flow in gap between two buildings in tandem configuration

Two buildings differing in height in tandem configuration are subjected to a turbulent boundary layer flow. The physical modelling in a wind tunnel has been performed, Particle Image Velocimetry in horizontal planes has been applied. The time-mean flow-field is dominated by the contrarotating vortex pair in the near-wake of the upstream building forming strong back-flow in this wake. Dynamical activity is located close to the bigger downstream building below the level of the smaller building roof. The dynamical structures in the space between them are studied using advanced analytical methods, Oscillation Pattern Decomposition (OPD). The 3 important OPD modes were detected differing by topology and frequency. The 2 OPD modes are characterized by vortical structures formed within the wake of the smaller upstream building and moving downstream towards the bigger building. The last OPD mode shows strong pulsation transversal flow in front of the bigger building. Typical frequency of the cyclo-stationary behaviour could be characterized by the Strouhal number in the range from 0.09 up to 0.15.