[GTP] IMAGe GTP Seminar--James Brasseur

[Silvia Gentile]

GTP Seminar

Application of Interactive Visualization-based Data Interrogation to 
Explore Local Dynamics of Vorticity in Shear-dominated Turbulence
James G. Brasseur
Department of Mechanical Engineering
Pennsylvania State University


The local dynamics of small-scale turbulence structure has a strong 
impact on clustering of particles, aerosol dynamics, cloud formation, 
reaction-rate chemistry, etc. Small-scale evolution centers on the 
interactions between local concentrations of vorticity and strain-rate 
fluctuations modulated by mean gradients. I shall discuss the 
incorporation of an interactive visualization-based data analysis 
environment into the statistical analysis of the local dynamics that 
causes isotropic small-scale turbulence to transition to shear-dominated 
small-scale turbulence. The data are from direct numerical simulations 
of initially isotropic turbulence under mean shear. The novel aspect of 
the analysis environment is the interactive integration of visualization 
with quantification of the interactions between individual vorticity and 
strain-dominated structures. Combined visualization-quantification 
originates from the “extraction” (i.e., identification of surface 
coordinates) of individual “structures” based on concentration, and the 
separation of the vorticity and strain-rate fields into objectively 
defined higher vs. lower intensity structures surrounded by low 
intensity fluctuations. Unlike traditional thresholding, our extraction 
algorithm includes lower-magnitude content that is part of the coherent 
structure. The structure-extraction algorithm was automated, and also 
integrated within an interactive environment where the user can extract 
potentially interesting structures by hand. We used the latter to follow 
the development of a single hairpin vortex in the shear-dominated state 
backwards in time to learn its origin in the isotropic state and the 
local dynamics that created it. The visualization of structures is 
integrated with statistical quantification. I shall present a number of 
interesting results from the integration of the visualization-based 
analysis environment with more classical statistics.

April28, 2009
Foothills Laboratory 2 (3450 Mitchell Lane), Room 1022
Lecture 10:30am
http://www.image.ucar.edu/Calendar/calendar08.shtml


Sent by Silvia Gentile, NCAR iMAGe