24-10-2012, 01:29 PM
Rapid Structured Volume Grid Smoothing and Adaption Technique
ABSTRACT
A rapid, structured volume grid smoothing and adaption technique, based on signal processing methods, was developed
and applied to the Shuttle Orbiter at hypervelocity flight conditions in support of the Columbia Accident Investigation.
Because of the fast pace of the investigation, computational aerothermodynamicists, applying hypersonic viscous flow solving
computational fluid dynamic (CFD) codes, refined and enhanced a grid for an undamaged baseline vehicle to assess a variety
of damage scenarios. Of the many methods available to modify a structured grid, most are time-consuming and require
significant user interaction. By casting the grid data into different coordinate systems, specifically two computational
coordinates with arclength as the third coordinate, signal processing methods are used for filtering the data [Taubin, CG v/29
1995]. Using a reverse transformation, the processed data are used to smooth the Cartesian coordinates of the structured grids.
By coupling the signal processing method with existing grid operations within the Volume Grid Manipulator tool, problems
related to grid smoothing are solved efficiently and with minimal user interaction. Examples of these smoothing operations
are illustrated for reduction in grid stretching and volume grid adaptation. In each of these examples, other techniques existed
at the time of the Columbia accident, but the incorporation of signal processing techniques reduced the time to perform the
corrections by nearly 60%. This reduction in time to perform the corrections therefore enabled the assessment of
approximately twice the number of damage scenarios than previously possible during the allocated investigation time.