Contribution of large-scale motions to the Reynolds shear stress in turbulent pipe flows

• DOI: 10.1016/j.ijheatfluidflow.2017.06.009
• Publication Date: 2017-06-29T22:36:44Z
• Authors: Junsun Ahn; Jinyoung Lee; Hyung Jin Sung
• Keywords: Reynolds stress; Magnetic Reynolds number

Abstract Direct numerical simulation data for turbulent pipe flows with Reτ = 544, 934, and 3008 were used to investigate the contribution of large-scale motions (LSMs) to the Reynolds shear stress. The relationship between viscous force ( d 2 U + / d y + 2 , VF) and turbulent inertia ( d 〈 − u ′ v ′ 〉 + / d y + , TI) results in a transition from the inner length scale to the intermediate length scale in the meso-layer. The acceleration force of the LSMs is balanced by the deceleration force of the small-scale motions (SSMs), which makes the zero TI at the wall-normal location of the maximum Reynolds shear stress (ym+). As the Reynolds number increases, the enhanced acceleration force of the LSMs expands the nearly zero TI region. The constant-stress layer is formed in the neighborhood of the zero TI, having the relatively strong VF. For sufficiently high Reynolds number flows, the log law is established beyond the meso-layer due to the fact that VF loses its leading order. The role of the LSMs in the wall-scaling behavior of ym+ is examined.