Case Studies

PORT-INJECTED FUEL SPRAY AND VAPOR ISO-SURFACES
Livonia, MI - November 2003

Contributed by: Doug Baker, Ph.D. President TECAT Engineering, Inc.

Using Tecplot, a shuttle debris trajectory is visualized. A 1.67 pound slab of insulating foam is seen falling off the external tank after Columbia's launch and hitting the left wing. The Columbia Accident Investigation Board (CAIB) has identified a debris event like this as the most likely cause of the Columbia disaster. This image was used in the CAIB's final report.

The Engineer
Michael Aftosmis works at the NASA Advanced Supercomputing (NAS) Division at NASA Ames Research Center. NAS was founded in 1984 to develop, demonstrate, and deliver innovative, distributed heterogeneous computing capabilities to enable NASA projects and missions.

Columbia Accident Investigation Board Results
The plot is a composite image extracted from a three-dimensional computational fluid dynamic simulation performed with Cart 3D, a comprehensive computer simulation program. The simulation was performed over the entire Space Transportation System (STS) launch configuration to support CAIB's investigation into the Columbia accident.

This image illustrates the computed trajectory for a piece of foam debris emanating from the bipod ramp. Calculations used the aerodynamic and mass properties of bipod ramp foam, coupled with the complex flow field during ascent, to determine the likely position and velocity histories of the foam.

The geometry is colored by surface pressure. The outlines of the reinforced carbon-carbon leading edge panels are overlayed on the orbiter wing leading-edge.

This data set was generated using 96 CPUs of NASA Ames' 1024 CPU SGI Origin 3000 — the largest shared memory system in the world. Approximately 400 such simulations were performed in support of the Columbia crash investigation between February and May of 2003.

Cart 3D
Cart 3D is an inviscid aerodynamic analysis package including surface modeling, mesh generation and flow simulation. The package performs automated mesh generation and flow solution around solid geometry imported directly from CAD models. The software package, an outgrowth of joint research at both NASA Ames and New York University, is a co-winner of NASA's "Software of the Year" award in 2002. It has been commercialized by ANSYS/ICEM CFD for private and commercial use in a variety of industries. Download a full description of Cart 3D (Cart3D.pdf 327 KB).

Cart 3D mesh generation visualized with Tecplot. Cart 3D's volume meshing is extremely fast - millions of cells are generated in minutes on desktop machines. This mesh was created in 55 seconds.

Other NAS Projects
Mike is part of a group that developed the AeroDB system, an automated CFD system running large parameter studies (a collection of computer jobs with a slightly different input for each job). AeroDB boils down the testing process of aerospace vehicle design, saving both time and money.

AeroDB Results
The plot below summarizes the results of several hundred Cart 3D simulations on the Liquid-Glide-Back-Booster (a conceptual design for a new, reusable launch vehicle). The plot shows the variation of lift with mach number and angle of attach. Each sphere in the plot represents one CFD run and is sized by the number of iterations in the run.

Several hundred CFD simulations summarized in one plot.

Tecplot
Automation is the major driver of Cart 3D and visualization. "We rely heavily on macros...and script almost everything," Mike says. "Macros create all of our plots, and Tecplot's TecIO library is called to plot simulation snapshots."

For the Columbia image, several snapshots are overlaid to produce the final image. Scripts and macros generated views of the debris simulation from various camera angles along with trajectory animations.

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