scholarly journals Antisymmetric quadrupole mode of coherent structures in wall-bounded turbulence

2013 ◽  
Vol 3 (5) ◽  
pp. 052002 ◽  
Author(s):  
Haiping Tian ◽  
Shaoqiong Yang ◽  
Lu Cheng ◽  
Yuan Wang ◽  
Nan Jiang
Keyword(s):  
Coherent Structures ◽  
Quadrupole Mode ◽  
Wall Bounded Turbulence

scholarly journals Coherent structures in wall-bounded turbulence

2018 ◽  
Vol 842 ◽  
Author(s):  
Javier Jiménez
Keyword(s):  
Coherent Structures ◽  
Reynolds Numbers ◽  
Turbulent Structures ◽  
Open Problems ◽  
Theoretical Understanding ◽  
Dispersive Waves ◽  
Guiding Principle ◽  
Large Structures ◽  
Logarithmic Layer ◽  
Wall Bounded Turbulence

This article discusses the description of wall-bounded turbulence as a deterministic high-dimensional dynamical system of interacting coherent structures, defined as eddies with enough internal dynamics to behave relatively autonomously from any remaining incoherent part of the flow. The guiding principle is that randomness is not a property, but a methodological choice of what to ignore in the flow, and that a complete understanding of turbulence, including the possibility of control, requires that it be kept to a minimum. After briefly reviewing the underlying low-order statistics of flows at moderate Reynolds numbers, the article examines what two-point statistics imply for the decomposition of the flow into individual eddies. Intense eddies are examined next, including their temporal evolution, and shown to satisfy many of the properties required for coherence. In particular, it is shown that coherent structures larger than the Corrsin scale are a natural consequence of the shear. In wall-bounded turbulence, they can be classified into coherent dispersive waves and transient bursts. The former are found in the viscous layer near the wall, and as very large structures spanning the entire boundary layer. Although they are shear-driven, these waves have enough internal structure to maintain a uniform advection velocity. Conversely, bursts exist at all scales, are characteristic of the logarithmic layer, and interact almost linearly with the shear. While the waves require a wall to determine their length scale, the bursts are essentially independent from it. The article concludes with a brief review of our present theoretical understanding of turbulent structures, and with a list of open problems and future perspectives.‘Chance is the name we give to what we choose to ignore (Voltaire)’

scholarly journals Coherent structures in wall-bounded turbulence

2015 ◽  
Vol 87 (2) ◽  
pp. 1161-1193 ◽  
Author(s):  
David J.C. Dennis
Keyword(s):  
Turbulent Flow ◽  
Turbulent Flows ◽  
Coherent Structures ◽  
Historical Research ◽  
Computational Techniques ◽  
Flow Visualisation ◽  
Inherent Difficulty ◽  
Turbulent Flow Field ◽  
Wall Bounded Turbulence

The inherent difficulty of understanding turbulence has led to researchers attacking the topic in many different ways over the years of turbulence research. Some approaches have been more successful than others, but most only deal with part of the problem. One approach that has seen reasonable success (or at least popularity) is that of attempting to deconstruct the complex and disorganised turbulent flow field into to a set of motions that are in some way organised. These motions are generally called "coherent structures". There are several strands to this approach, from identifying the coherent structures within the flow, defining their characteristics, explaining how they are created, sustained and destroyed, to utilising their features to model the turbulent flow. This review considers research on coherent structures in wall-bounded turbulent flows: a class of flow which is extremely interesting to many scientists (mainly, but not exclusively, physicists and engineers) due to their prevalence in nature, industry and everyday life. This area has seen a lot of activity, particularly in recent years, much of which has been driven by advances in experimental and computational techniques. However, several ideas, developed many years ago based on flow visualisation and intuition, are still both informative and relevant. Indeed, much of the more recent research is firmly indebted to some of the early pioneers of the coherent structures approach. Therefore, in this review, selected historical research is discussed along with the more contemporary advances in an attempt to provide the reader with a good overview of how the field has developed and to highlight the perspicacity of some of the early researchers, as well as providing an overview of our current understanding of the role of coherent structures in wall-bounded turbulent flows.

Sign in / Sign up

Export Citation Format

Share Document