Generation and characterization of a non-stationary flow field in a small-scale wind tunnel using a multi-blade flow device

Physical experimentation for non-stationary wind phenomena has been the focal point of much research. Replication of transient, non-synoptic wind events such as thunderstorm downbursts and tornadoes require innovative means that break from traditional boundary-layer wind tunnel experiments. This paper examines the feasibility of a multi-blade flow device capable of reproducing the gust front of a non-stationary outflow. The device is inserted into the test chamber of the small-scale, closed-circuit wind tunnel at Northeastern University. Replication of spatial and temporal features of a non-stationary gust front (slowly-varying flow and turbulence fluctuations) is investigated through velocity measurements at various elevations. The wind velocity record from the Andrews Air Force Base downburst is employed for verification of the experimental procedure; its physical effects on a tall building model are recorded. The results suggest that this device may be used to simulate the main features of simplified non-stationary gust fronts in a conventional wind tunnel without significant modifications to the test chamber.