A new identification method in sampled quadrant analysis for wall-bounded turbulence

In this paper, a new identification method in sampled quadrant analysis was introduced to single out the larger ejection-type (Q2) and sweep-type (Q4) motions which directly contribute to the total Reynolds shear stress in an average sense. Different from previous ones, the threshold Rc in the present method is not an adjustable parameter, but a determined value by data. The singled-out objects by using the present method form 3D “force structures” that directly contribute to the skin-friction coefficient.