Unsteady Flow Analysis Toolkit (UFAT)

Introduction

The Unsteady Flow Analysis Toolkit (UFAT) software program is a pioneer tool for visualizing very large time-dependent (or "unsteady") flow data sets from Computational Fluid Dynamics (CFD) simulations. For example, UFAT has been used to process and analyze high-fidelity, time-dependent simulation results of the Space Shuttle, military and commercial aircraft, artificial heart devices, and many more. Unsteady CFD simulations are used to study how fluids interact with engineering structures and are frequently used to predict and understand the aerodynamic behavior of aerospace vehicles. The UFAT software can analyze large-scale CFD computer simulation results with little or no human intervention, and reveal crucial flow structures such as vortices and shock waves. This software effectively reduces the analysis time of multi-gigabyte datasets from weeks to hours using state-of-the-art particle tracking and feature extraction algorithms developed at NASA Ames Research Center.

General Description

UFAT provides aerospace engineers and scientists with a suite of visualization tools that were designed and optimized for time-dependent simulations. Many innovative visualization tools were prototyped and tested in this software package during its five-year development period. These include:

1. time-dependent particle and debris tracking,
2. vortex core extraction,
3. stream ribbon and surface visualization,
4. surface flow visualization, and
5. tetrahedral decomposition for optimal processing.

UFAT supports PLOT3D format multi-block curvilinear grids with moving geometry. The following visualization techniques are provided in UFAT:

Stream lines
Path lines
Streak lines
Time lines
Stream surfaces and ribbons
Scalar/smooth shaded color contoured grid surfaces
Vector plot
Vortex core detection
Surface flows

UFAT does not provide a graphical user interface; all graphics results are saved to a metafile for playback. The graphics metafile can be displayed using FAST . UFAT allows a job to run in several sessions and can handle hundreds of timesteps of the flow data.

Animations

Many CFD scientists have used UFAT to analyze their unsteady flow data. Click on any one of the following icons to see some of the animations created for their flow analyses.

V-22 Tiltrotor (0.6 MB)

Robert Meakin of Army Aeroflightdynamics used UFAT to compute streak lines about the V-22 tiltrotor aircraft, which consists of 1.5 million grid points and each rotor blade revolution consists of 1,450 time steps. Surface of the tiltrotor is colored by pressure and particles are colored by time.

SOFIA (2.6 MB)

SOFIA, which stands for Stratospheric Observatory For Infrared Astronomy (SOFIA), is a modified Boeing 747SP transport with a large cavity that holds a three-meter telescope. Chris Atwood used streaklines to assist the assessment of safety and optical performance of a large cavity in the 747SP. SOFIA consists of approximately 4 million grid points in 41 grid blocks.

Missile (0.7 MB)

Shown here are two stream surfaces surrounding a missile body configuration. By candy striping the stream surfaces, flow rotation is easily seen. The unsteady flow dataset was computed by Carl Hsieh of Naval Surface Weapons Center.

A comparison of three different flow visualization techniques: Stream lines (3.7 MB) , Streak lines (3.6 MB) , and Time lines (5.0 MB), were made using unsteady flows about an ogive cylinder body. The comparison demonstrated that an instantaneous flow visualization technique (streamlines) may not be effective as time-dependent flow visualization techniques (streak lines and time lines). For the comparison results, see NAS Technical Report NAS-96-001. The flow data set was computed by Scott Murman.

Airfoil (3.7 MB)

Streak lines and time lines are time-dependent particle tracing techniques that are very effective for visualizing unsteady flows. Sungho Ko used these two techniques to visualize his unsteady flow data surrounding an oscillating airfoil.

Rolling Delta Wing (1.3 MB)

Neal Chaderjian used UFAT to compute vortex cores and streak lines about a rolling delta wing. The vortex cores are shown in yellow and the streaklines are shown in magenta.

Images

Instantaneous velocity magnitude and vortex core lines for pulsatile flow through Ventricular Assist Device (VAD) inlet cannula. (Courtesy of Dr. Cetin Kiris)

(Click on image for larger view)

Filaments of particles released every 25 time-steps of simulation (post-process) to visualize rotor-wake system. (Courtesy of Dr. Robert Meakin)

Vortex cores about a Delta Wing (Click on image for larger view)

The above figure depicts vortex cores overlaid with streak lines. The vortex cores are represented by yellow line segments and the streak lines are represented by red particles.

(Click on image for larger view)

A close-up view of streaklines near the SOFIA telescope without the aircraft body. The particles are colored by the time of their release (blue denotes the earliest time and orange denotes the most recent time) from a rake positioned in the aperture of the cavity. Some particles are trapped inside the cavity while some have escaped and passed the empennage.

Vortex cores about an F18 fighter jet (Click on image for larger view)

The above figure depicts vortex cores overlaid with streak lines. The vortex cores are represented by black line segments and the streak lines are colored by time at release.

Software Request

If you are interested in obtaining UFAT, see Software Request

Papers

D.N. Kenwright and R. Haimes, Vortex Identification - applications in aerodynamics, in proc. IEEE/ACM Visualization '97, Phoenix, Arizona, October 1997.
D. Lane, Scientific Visualization of Large Scale Unsteady Fluid Flows," in Scientific Visualization: Overviews, Methodologies and Techniques, IEEE CS Press, 1996.
D. N. Kenwright and D. A. Lane, Interactive time-dependent particle tracing using tetrahedral decomposition, IEEE Transactions on Visualization and Computer Graphics, V. 2, No. 2, Jun. 1996, pp. 120-129.
D. A. Lane, Visualizing Time-Varying Phenomena in Numerical Simulations of Unsteady Flows, 34th Aerospace Sciences Meeting and Exhibit, Reno, Nevada, January 1996, AIAA-96-0048.
D. N. Kenwright and D. A. Lane, Optimization of Time-Dependent Particle Tracing Using Tetrahedral Decomposition, Proceedings of IEEE Visualization '95, October 1995, pp. 321-328.
D. A. Lane, Visualization of Numerical Unsteady Fluid Flows, Proceedings of Sixth International Symposium on Computational Fluid Dynamics, September 1995.
D. A. Lane, Parallizing a Particle Tracer for Flow Visualization, Seventh SIAM Conference on Parallel Processing for Scientific Computing, February 1995, pp. 784-789.
D. A. Lane, UFAT - A Particle Tracer for Time-Dependent Flow Fields, Proceedings of IEEE Visualization '94, Washington D.C., October 1994, pp. 257-264.
D. A. Lane, Visualization of Time-Dependent Flow Fields", Proceedings of IEEE Visualization '93, San Jose, October 1993, pp. 32-38.


	Friday, 30-Aug-2002 16:50:30 WebWork: David Kao NASA Responsible Official: David Kao