Part of the book: Wind Tunnels and Experimental Fluid Dynamics Research
This chapter is focused on vortex detection, generation, and characterization. There are many ways to generate and characterize vortex; this chapter is focused on two techniques to generate a vortex, with fixed surface, often called vortex generators (VG), and with blowing air. Vortex detection is one of the major problems in fluid dynamics and usually some characteristics of the vortex must be known in order to detect them; once, the vortex is detected, a velocity analysis is helpful to characterize it. Most characterization techniques involves the comparison of some known properties of vortex, such as velocity field, vorticity field or tensor, turbulence intensity, etc. The technique to be used to characterize a vortex is closely related to the data that one possesses. In measuring methods such as particle image velocimetry (PIV), there are algorithms that can easily detect size and vortex centers, relaying in velocity and vorticity. This chapter focuses on detection by analyzing velocity signals, via wavelet transform and statistical properties. When it is not possible to characterize a vortex because it does not have a coherent structure, another approach must be used such as defining turbulence intensities and zone of influence of the vorticose structure.
Part of the book: Swirling Flows and Flames