Use of a quadrant analysis technique to identify coherent structures in a turbulent boundary layer

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Abstract
A quadrant analysis technique based on instantaneous products uv, uϑ, and vϑ (u, v are the longitudinal and normal velocity fluctuations, ϑ is the temperature fluctuation) is used to obtain averages, in ejection and sweep quadrants, associated with coherent structures contributing significantly to Reynolds stress and heat flux in a turbulent boundary layer. Conditional averages of u, v, ϑ and products uv, uϑ, and vϑ in ejection and sweep quandrants indicate only partial qualitative agreement with those obtained by other conditional sampling techniques, with detection based on the internal front characterized by rapid changes in velocity and temperature. Although the frequency of occurrence of ejections is nearly equal to that of sweeps, only a small percentage of the total number of ejections is followed by sweeps, whereas the percentage of ejections following sweeps is negligible.