The Influence of Polymers on Coherent Structures in Decaying Homogeneous Isotropic Turbulence

2010 ◽  
Author(s):  
Wei-Hua Cai ◽  
Hong-Na Zhang ◽  
Feng-Chen Li
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Drag Reduction ◽  
Coherent Structures ◽  
Isotropic Turbulence ◽  
Polymer Additives ◽  
Fine Scale ◽  
Reduction Mechanism ◽  
Homogeneous Isotropic Turbulence ◽  
Increase Rate

Drag reduction in decaying homogeneous isotropic turbulence (DHIT) with polymer additives has been observed, which leads to weaker turbulent characteristic quantities. Coherent structures play an important role in the understanding of turbulent dynamics, and the introduction of polymer additives can significantly modify their behavior. It is believed the modifications are closely related to drag reduction mechanism. In the present study, we mainly focus on investigating the influence of polymers on coherent structures from phenomenological and energetic viewpoint for DHIT with polymers based on direct numerical simulation (DNS). The results show that polymers can not only suppress the increase rate of the enstrophy and strain but also their productions, leading to a remarkable inhibition of coherent structures especially at fine scale.

scholarly journals Direct Numerical Simulation in Two Dimensional Homogeneous Isotropic Turbulence Using Spectral Method

2013 ◽  
Vol 5 (3) ◽  
pp. 435-445
Author(s):  
M. S. I. Mallik ◽  
M. A. Uddin ◽  
M. A. Rahman
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Flow Field ◽  
Direct Numerical Simulation ◽  
Spectral Method ◽  
Isotropic Turbulence ◽  
Qualitative Behavior ◽  
Two Dimensional ◽  
Homogeneous Isotropic Turbulence ◽  
Decaying Turbulence

Direct numerical simulation (DNS) in two-dimensional homogeneous isotropic turbulence is performed by using the Spectral method at a Reynolds number Re = 1000 on a uniformly distributed grid points. The Reynolds number is low enough that the computational grid is capable of resolving all the possible turbulent scales. The statistical properties in the computed flow field show a good agreement with the qualitative behavior of decaying turbulence. The behavior of the flow structures in the computed flow field also follow the classical idea of the fluid flow in turbulence. Keywords: Direct numerical simulation, Isotropic turbulence, Spectral method. © 2013 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. doi:http://dx.doi.org/10.3329/jsr.v5i3.12665 J. Sci. Res. 5 (3), 435-445 (2013)  

A physical mechanism of the energy cascade in homogeneous isotropic turbulence

2008 ◽  
Vol 605 ◽  
pp. 355-366 ◽  
Author(s):  
SUSUMU GOTO
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Transfer Rate ◽  
Physical Mechanism ◽  
Isotropic Turbulence ◽  
Scale Space ◽  
Energy Cascade ◽  
Homogeneous Isotropic Turbulence ◽  
Moderate Reynolds Number

In order to investigate the physical mechanism of the energy cascade in homogeneous isotropic turbulence, the internal energy and its transfer rate are defined as a function of scale, space and time. Direct numerical simulation of turbulence at a moderate Reynolds number verifies that the energy cascade can be caused by the successive creation of smaller-scale tubular vortices in the larger-scale straining regions existing between pairs of larger-scale tubular vortices. Movies are available with the online version of the paper.

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