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CFD Events Calendar, Event Record #19737

New Theory on Turbulence Generation and Sustenance
New Theory on Turbulence Generation; Large Eddy Simulation for Supersonic Micro Vortex Generator
Date: February 27, 2014
Location: B235 R1090 Gold Room, Arlington, Texas, United States
Web Page:
Contact Email:
Organizer: Greg Burton
Special Fields: Turbulence Modeling, Turbulence Theory, Turbulence - LES Methods, Aerodynamics, Numerical Methods, Instabilities and Flow Control, Fluid Mechancis, Theoretical Fluid Dynamics, Boundary and Interior Layers, Scientific Computing, Transition
Deadlines: February 27, 2014 (registration)
Type of Event: Seminar, International

This presentation serves as a systematic report on our 
recent new DNS study on physics of late boundary layer
transition. This includes mechanism of the large coherent 
vortex structure formation, small length scale
generation and flow disordering. The widely spread 
concept "vortex breakdown to turbulence", which was
considered as the last stage of flow transition, is not 
observed. We proposed a new theory on boundary layer
transition with five steps, i.e. receptivity, linear 
instability, large vortex formation, small length scale
generation, loss of symmetry and being chaotic to 
turbulence. We have also proposed a new theory about
turbulence generation and sustenance. The new theory shows 
that all small length scales (turbulence) are
generated by shear layer instability which is produced by 
large vortex structure with multiple level vortex
rings, multiple level sweeps and ejections, and multiple 
level negative and positive spikes near the laminar 
Therefore, "turbulence" is not generated by "vortex 
breakdown" but rather positive and negative spikes
and consequent high shear layers. "Shear layer instability" 
is considered as the "mother of turbulence". This
new theory may give a universal mechanism for turbulence 
generation and sustenance - the energy is brought
by large vortex structure through multiple level sweeps not 
by "vortex breakdown". When the Reynolds
number is large enough fluid shear, which is unstable, is 
dominant in laminar boundary layer and fluid rotation,
which is stable, is dominant in turbulent boundary layer. 
In other words, laminar boundary layer is an unstable
state, but turbulent is a stable state, and thus transition 
from laminar to turbulent is unavoidable. More other
new physics have also been discussed.
Event record first posted on March 21, 2014, last modified on March 23, 2014

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