Active generation of large scale turbulence in a boundary layer wind tunnel

Abstract

The effect of turbulence on bluff body aerodynamics and response in wind flow has been increasingly studied for a wide range of turbulence integral scale. The generation of large turbulence scale using passive methods with vorticity generators (turbulence grid or trip board) is usually limited by the height and width of the wind tunnel. It is therefore essential to actively supply additional energy to the flow to generate large fluctuations in the wind. Among few active modeling techniques, this paper describes a simple actively controlled method by oscillating a large trip board in the upstream section of the wind tunnel to generate large turbulence length scales of magnitudes up to almost 6 times the maximum length scale obtainable by passive methods in the same wind tunnel. By using this active generation technique, a large longitudinal turbulence length scale up to 0.8m has been achieved at the height of 53mm above the tunnel floor in the 12m wide by 4m high working section of the 1MW Boundary Layer Wind Tunnel at Monash University, which can be used to model more realistically the atmospheric turbulence effects on large structures and air pollutant dispersion studies