scholarly journals Polymer induced drag reduction in exact coherent structures of plane Poiseuille flow

2007 ◽  
Vol 19 (8) ◽  
pp. 083101 ◽  
Author(s):  
Wei Li ◽  
Michael D. Graham
Keyword(s):  
Drag Reduction ◽  
Poiseuille Flow ◽  
Coherent Structures ◽  
Plane Poiseuille Flow ◽  
Induced Drag

scholarly journals Streamwise and doubly-localised periodic orbits in plane Poiseuille flow

2014 ◽  
Vol 761 ◽  
pp. 348-359 ◽  
Author(s):  
Stefan Zammert ◽  
Bruno Eckhardt
Keyword(s):  
Periodic Orbits ◽  
Poiseuille Flow ◽  
Coherent Structures ◽  
Wave Structure ◽  
Edge State ◽  
Travelling Wave ◽  
Spanwise Direction ◽  
Plane Poiseuille Flow ◽  
Streamwise Direction ◽  
Extended States

AbstractWe study localised exact coherent structures in plane Poiseuille flow that are relative periodic orbits. They are obtained from extended states in smaller periodically continued domains, by increasing the length to obtain streamwise localisation and then by increasing the width to achieve spanwise localisation. The states maintain the travelling wave structure of the extended states, which is then modulated by a localised envelope on larger scales. In the streamwise direction, the envelope shows exponential localisation, with different exponents on the upstream and downstream sides. The upstream exponent increases linearly with Reynolds number $\mathit{Re}$, but the downstream exponent is essentially independent of $\mathit{Re}$. In the spanwise direction the decay is compatible with a power-law localisation. As the width increases the localised state undergoes further bifurcations which add additional unstable directions, so that the edge state, the relative attractor on the boundary between the laminar and turbulent motions, in the system becomes chaotic.

scholarly journals Fibre-induced drag reduction

2008 ◽  
Vol 602 ◽  
pp. 209-218 ◽  
Author(s):  
J. J. J. GILLISSEN ◽  
B. J. BOERSMA ◽  
P. H. MORTENSEN ◽  
H. I. ANDERSSON
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Drag Reduction ◽  
Elastic Layer ◽  
Turbulent Drag Reduction ◽  
Rigid Polymer ◽  
Fibre Concentration ◽  
Induced Drag ◽  
Turbulent Drag

We use direct numerical simulation to study turbulent drag reduction by rigid polymer additives, referred to as fibres. The simulations agree with experimental data from the literature in terms of friction factor dependence on Reynolds number and fibre concentration. An expression for drag reduction is derived by adopting the concept of the elastic layer.

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