Four-Quadrant Classification Method

Turbulent motions in single-phase boundary layers, pipe flows, and jets are not completely random but have coherent or ordered structure [42-45], According to the four-quadrant classification method, the turbulent motions are grouped into four distinct categories, as illustrated in Fig. 2.24. In this figure, ejection denotes a higher momentum fluid motion directed outward, outward interaction denotes a lower momentum fluid motion directed outward, sweep denotes a lower momentum 

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As shown in the previous section, the shape of bubbles was found to affect preferably the modulation of radial (horizontal) turbulence component [24]. However, the mechanism of turbulence production was not mentioned. In this section, the application is described of the four-quadrant classification method, [39] one of the most popular conditional sampling methods, adopted to elucidate the coherent structure of turbulence or the mechanism of turbulence production in a He-Wood s metal bubbling jet. 

Experimental Results Based on Four-Quadrant Classification Method... 

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