scholarly journals Dynamic K-L analysis of coherent structures based on DNS of turbulent Newtonian and viscoelastic flows (Poster Presentation)

PAMM ◽  
2007 ◽  
Vol 7 (1) ◽  
pp. 2120037-2120038
Author(s):  
Gaurab Samanta ◽  
Geoffrey Oxberry ◽  
Antony N. Beris ◽  
Robert Handler ◽  
Kostas Housiadas
Keyword(s):  
Poster Presentation ◽  
Coherent Structures ◽  
Viscoelastic Flows

scholarly journals Dynamic K-L analysis of coherent structures based on DNS of turbulent Newtonian and viscoelastic flows

PAMM ◽  
2007 ◽  
Vol 7 (1) ◽  
pp. 2100085-2100086
Author(s):  
Gaurab Samanta ◽  
Geoffrey Oxberry ◽  
Antony N. Beris ◽  
Robert Handler ◽  
Kostas Housiadas
Keyword(s):  
Coherent Structures ◽  
Viscoelastic Flows

Time-evolution K–L analysis of coherent structures based on DNS of turbulent Newtonian and viscoelastic flows

2008 ◽  
Vol 9 ◽  
pp. N41 ◽  
Author(s):  
Gaurab Samanta ◽  
Geoffrey M. Oxberry ◽  
Antony N. Beris ◽  
Robert A. Handler ◽  
Kostas D. Housiadas
Keyword(s):  
Time Evolution ◽  
Coherent Structures ◽  
Viscoelastic Flows

Dilute Polymers and Coherent Structures in Wall Turbulence

1999 ◽  
Author(s):  
Elisabetta De Angelis ◽  
Carlo M. Casciola ◽  
Renzo Piva
Keyword(s):  
Coherent Structures ◽  
Wall Layer ◽  
Wall Turbulence ◽  
Viscoelastic Flows ◽  
Mean Velocity ◽  
Newtonian Flows ◽  
Level Of Activity ◽  
Main Effect ◽  
The Mean ◽  
Low Speed Streaks

Abstract Both numerical and experimental data confirm that the introduction of dilute polymers in a turbulent flow changes some mean characteristics of the flow: the wall drag can decrease up to 40% while the average spacing among streaks can even double. Actually a link exists between streaks spacing and mean velocity gradient at the wall. In such viscoelastic flows the wall turbulence regeneration is still influenced by the mean shear and by the interaction of the coherent structures even if they appear more ordered and larger with respect to Newtonian flows. These phenomena, which have been repeatedly observed since the findings of Toms, would require a better understanding of the mechanisms that locally induce this behaviour. The analysis of data from direct numerical simulation with FENE-P model for the polymers, seems to suggest, as the main effect of the viscoelastic reaction, a stabilizing action on the low speed streaks and a related decrease in the population of the wall layer coherent structures. The decreased level of activity induces relevant changes in the scales of the turbulence and originates the observed drag reduction.

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