Visualization and feature extraction in isotropic
Navier-Stokes turbulence
Part of HPCD, supported by ARPA
Victor M. Fernandez, Norman J. Zabusky,
Smitha Bhat, Deborah Silver,
Shi-Yi Chen
Abstract
We present feature extraction and data reduction algorithms and
provide an insight in the types of problems that arise in dealing with
large datasets, obtained in Navier-Stokes turbulence simulations with a
512^3 mesh resolution. The developed tools are based on
thresholding, object segmentation and low order ellipsoidal
quantifications and are applied to the search of coherent vortex
structures associated with maxima events in the turbulence field. We
underline the importance of sharing tasks between the supercomputer
(CM5) and the workstation (SGI Onyx), where each machine may work more
efficiently at different stages of the data processing. We obtain
visualizations that show the structure of the dominant coherent
objects. The reduced representations employed make it possible to
examine different types of fields for possible correlations. The
quantification of the objects identified by the feature extraction
algorithms, should contribute to the building of models that consider
both coherent structures and the random background observed in
Navier-Stokes turbulence.
Figures
Isosurface animation (500Kb)
Ellipsoid fitting animation (700Kb)
Fig. 1 Turbulence 512^3 dataset. The vorticity
magnitude field shown in this figure is represented by spheres
corresponding to a set of thresholded points (20% of the maximum and
above).
Fig. 3 The object-segment code separates
the objects found at a given threshold. The classification of the
objects is shown in the figure by coloring them according to the local
vorticity magnitude maxima inside each object. The program allows the user
to select single objects for further quantification.
Fig. 6 Run of the CMAVS module:
The diagnostic box is sent across the network
(CM5-NCSA/Onyx-VIZLAB) with a 64^3 vorticity magnitude subdomain.
The reports on the execution of the remote CMAVS module my_r_s_cm
are also included.
Fig. 9 The spheres
representation is used to visualize the vorticity
magnitude field inside the diagnostics box.
Fig. 10 After the diagnostics box
(in this case 200^3) is produced, standard AVS modules, like
isosurface in this figure, can be used.
Fig. 11 Use of the list of identified objects:
The list of identified
objects, represented by the ellipsoids (scatter module) is used to
guide the search of relevant vortex structures using the diagnostics
box (smabox module).
Fig. 12 First view of
the maximum vorticity magnitude object. The isosurface in the upper
figures represents the vorticity magnitude. In the lower figures, the
isosurface represents the strain-rate magnitude. The lines trace the
vorticity field and are released from the ellipsoids, which fit the
vorticity magnitude maxima regions.
Fig. 13 Second view of
the maximum vorticity magnitude object.
Fig. 14 View of the object 12, according to the classification
obtained by the scatter module.
This work is an interdisciplinary effort and part of the
Hypercomputing and Design (HPCD) project, supported by ARPA, contract
DABT-63-93-C-0064. Norman J. Zabusky (nzabusky@caip.rutgers.edu),
Deborah Silver (silver@caip.rutgers.edu), Victor M. Fernandez
(victor@caip.rutgers.edu) and Smitha Bhat (sbhat@caip.rutgers.edu) of
the Laboratory for Visiometrics and Modeling (VIZLAB), Rutgers
University coordinate the fluid dynamics and visiometrics and the
turbulence simulation is produced by Shiyi Chen (syc@lanl.gov) at Los
Alamos National Laboratory. Parallel simulations were performed on
the CM5 machines at ACL-LANL and NCSA.
victor@caip.rutgers.edu
Fig. 1 Turbulence 512^3 dataset. The vorticity
magnitude field shown in this figure is represented by spheres
corresponding to a set of thresholded points (20% of the maximum and
above).
Fig. 3 The object-segment code separates
the objects found at a given threshold. The classification of the
objects is shown in the figure by coloring them according to the local
vorticity magnitude maxima inside each object. The program allows the user
to select single objects for further quantification.
Fig. 6 Run of the CMAVS module:
The diagnostic box is sent across the network
(CM5-NCSA/Onyx-VIZLAB) with a 64^3 vorticity magnitude subdomain.
The reports on the execution of the remote CMAVS module my_r_s_cm
are also included.
Fig. 9 The spheres
representation is used to visualize the vorticity
magnitude field inside the diagnostics box.
Fig. 10 After the diagnostics box
(in this case 200^3) is produced, standard AVS modules, like
isosurface in this figure, can be used.
Fig. 11 Use of the list of identified objects:
The list of identified
objects, represented by the ellipsoids (scatter module) is used to
guide the search of relevant vortex structures using the diagnostics
box (smabox module).
Fig. 12 First view of
the maximum vorticity magnitude object. The isosurface in the upper
figures represents the vorticity magnitude. In the lower figures, the
isosurface represents the strain-rate magnitude. The lines trace the
vorticity field and are released from the ellipsoids, which fit the
vorticity magnitude maxima regions.
Fig. 13 Second view of
the maximum vorticity magnitude object.
Fig. 14 View of the object 12, according to the classification
obtained by the scatter module.