Visualizing Large Eddy Simulations

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April 13, 2015
DNS of Spatially Developing Turbulent
Boundary Layers
PI: Antonino Ferrante, University of Washington
ECSS: Darren Adams, David Bock, NCSA
Science Overview
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Computational fluid flow at boundary layers
Solution of 3D, unsteady Navier-Stokes (NS)
Generate initial inflow conditions to DNS
Velocity components must satisfy NS
Reference: http://dx.doi.org/10.1016/j.jcp.2004.01.016
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XSEDE project
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SU hrs and TB on Kraken, Ranger, tape storage
Simulation using largest Reynolds number ever reported
Share generated DNS database with scientific community
Perform first DNS of fully-resolved droplet-laden turbulence
ECSS consultants: Darren Adams, David Bock (NCSA)
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ECSS goals
• Petascale scaling and deployment on XSEDE resources
• High-level HDF5 parallel IO library layer (H5DNS)
• H5DNS provides
– Data creation via petascale simulation runs
– Data analysis
– Simplified I/O data conversion (e.g. visualization)
• Visualization tests per simulation run
• Production visualization imagery (e.g. journals, conferences)
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H5DNS software
• IO library written in C on top of HDF5 library.
• Encapsulates HDF5 File structure and metadata particular to
the DNS simulation.
• For simulation code, H5DNS provides:
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Large data dumps of field variables
Restart capability
Particle IO
Metadata (run vars., input parameters etc.)
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H5DNS software
• Analysis and visualization
– VisIt Reader (C++)
– Other direct HDF5 access (Matlab,TecPlot,…)
– Swig interfaces ??? (Perl , Python,…)
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Visualization
Data input
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Before H5DNS, data generation cumbersome, error-prone
Required editing and executing Fortran post-processor
Simple H5DNS reader now used to read and extract data
Converted to format used by custom visualization system
Interested in scalar Lambda2 (vortices using velocity tensors)
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Visualization
Initial representation
• Tests verifying data conversion using slice planes
• Lambda2 (left) and velocity magnitude (right)
• Note small structures in lambda2
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Visualization
Isolating structure
• Transfer function to isolate narrow Lambda2 range
• Evident are very small tubular structures
• Colormap with gaussian hue and alpha functions
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Visualization
Volume rendering tests
• Ray-traced, volume renderings using same colormap
• Looking down chamber (left) and close-up side view (right)
• Note small, wispy tubular structures
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Visualization
Volume rendering tests
• Testing different visual representations
• Top-down view (left), three-quarter side view (right)
• Added data boundary grid for reference
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Visualization
Production sequences
• Lighting and shadows added
• Increased absorption coefficients
• Multiple viewing angles
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Visualization
Production sequences
• Lighting and shadows added
• Increased absorption coefficients
• Multiple viewing angles
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Visualization
Future work
• Integration of particle flow visualizing velocity
• Example of previous particle flow using custom system
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