Turbulent flow in eccentric annular pipe

The results of direct numerical simulations of turbulent flow through a pipe with an eccentric annular cross-section are presented. The simulations were performed at Re = 4000 (where the Reynolds number Re is based on the bulk velocity and hydraulic diameter) using an energy-conserving finite-difference method. It was found that two types of flow develop depending on the geometric parameters. In the flow of first type, turbulent fluctuations are observed over the entire cross-section of the pipe, including the narrowest gap, where the local Reynolds number is only about 500. The flow in the another type is divided into turbulent and laminar regions (in the wide and narrow parts of the gap, respectively). Eccentric annular pipe presents a convenient model for study inhomogeneous turbulent flow, peculiarities of the flow in the neighborhood of the laminar/turbulent interface and the related entrainment phenomenon.