Influence of wall-attached structures on the interface of the quiescent core region in turbulent pipe flow

The quiescent core region in pipe flow is explored using the direct numerical simulation data of turbulent pipe flow at Reτ = 926. The quiescent core region is one of the uniform momentum zones and contains the highest convection velocity in turbulent pipe flow. The interface of the quiescent core region has a similar physical behavior to the turbulent/non-turbulent interface and underlying internal layer. The turbulent structures in pipe flow are detected by using the percolation theory. The wall-attached structure is closely associated with geometrical characteristics of the interface and entrainment, which is a transport phenomenon at the interface. The wall-attached structure has a huge influence on dynamics in the vicinity of the interface. The wall-attached u-structure acquired in the present work is a structure that is subject to the attached-eddy hypothesis, and the influence of the wall-attached structures near the interface varies according to height change of the wall-attached structures. Finally, dynamics of the interface is reconstructed using conditional statistics according to the growth of the wall-attached structure.