An Experimental Technique for the Generation of Large-Scale Spanwise Vortices in a Wind Tunnel
نویسندگان
چکیده
The presence of large-scale vortices with high spanwise coherence has been observed in the atmospheric boundary layer (ABL). This study investigates an innovative technique to generate a large-scale spanwise vortex from the oscillation of a surface-mounted fence in a wind tunnel. Characteristics of the large vortex with a well-defined length scale and its development with downstream distance behind the fence were investigated. Time-averaged profiles of velocity, normal and Reynolds stresses were measured to determine the dominant frequencies of the large vortices in the wake of the oscillating fence. Longitudinal length scales of the spanwise vortices were calculated using the autocorrelation of velocity data. It was found that the size of the largest spanwise vortices are most significantly influenced by the height of the fence, such that the integral length scales increased by 52mm for a 20mm increase in fence height. Spanwise vortices were also found to be 11mm larger when oscillating the fence at the vortex shedding frequency behind a stationary fence. The oscillation amplitude of the fence was found to have a negligible effect on the size of the large spanwise vortices.
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