Stability of flow through a slowly diverging pipe

缓慢扩张管道中的湍流转捩

Transition to turbulence in slowly divergent pipe flow

本文通过实验与数值模拟研究缓慢扩张管道中的流动，发现轴对称锥形回流区及临界速度，并揭示其湍流转捩是突扩与直圆管流动中多个阶段的组合。

具有非缓变截面和边界滑移的轴对称管内毛细流动的流体动力学模型

A hydrodynamic model of capillary flow in an axially symmetric tube with a non-slowly-varying cross section and a boundary slip

本文结合Stokes方程与Hagen-Poiseuille流动模型，推导出非缓变截面管内毛细流动的一般公式，并给出锥形管、幂律形扩张管和收缩管中弯月面演化的新标度公式，为流体二极管和开关等器件设计提供理论依据。

Three dimensional simulations of viscous folding in diverging microchannels

Three dimensional simulations on the viscous folding in diverging microchannels reported by Cubaud and Mason are performed using the parallel code BLUE for multi-phase flows. The more viscous liquid L_1 is injected into the channel from the center inlet, and the less viscous liquid L_2 from two side inlets. Liquid L_1 takes the form of a thin filament due to hydrodynamic focusing in the long channel that leads to the diverging region. The thread then becomes unstable to a folding instability, due to the longitudinal compressive stress applied to it by the diverging flow of liquid L_2. Given th…

在扩张或收敛壁面之间流动的粘性流体浅层流

Shallow current of viscous fluid flowing between diverging or converging walls

本文研究幂律变宽通道中粘性流体的浅层流入与流出，通过润滑理论、相平面和MOL数值模拟得到两类相似解，并揭示其收敛与渐近特性。

Dynamics of propagating turbulent pipe flow structures. Part II: Relaminarization

The dynamical behavior of propagating structures, determined from a Karhunen-Lo`eve decomposition, in turbulent pipe flow undergoing reverse transition to laminar flow is investigated. The turbulent flow data is generated by a direct numerical simulation started at a fully turbulent Reynolds number of Re_τ=150, which is slowly decreased until Re_τ=95. At this low Reynolds number the high frequency modes decay first, leaving only the decaying streamwise vortices. The flow undergoes a chugging phenomena, where it begins to relaminarize and the mean velocity increases. The remaining propagating m…

Experimental assessment of drag reduction by traveling waves in a turbulent pipe flow

We experimentally assess the capabilities of an active, open-loop technique for drag reduction in turbulent wall flows recently introduced by Quadrio et al. [J. Fluid Mech., v.627, 161, (2009)]. The technique consists in generating streamwise-modulated waves of spanwise velocity at the wall, that travel in the streamwise direction. A proof-of-principle experiment has been devised to measure the reduction of turbulent friction in a pipe flow, in which the wall is subdivided into thin slabs that rotate independently in the azimuthal direction. Different speeds of nearby slabs provide, although i…