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Curtis C. Ober Senior Member of the Technical StaffParallel Computational Science |
Curtis C. Ober MS 1111 Parallel Computational Sciences, Dept. 9221 Sandia National Laboratories P.O.Box 5800 Albuquerque, NM 87185-1111 U.S.A. |
Email: ccober@cs.sandia.gov Phone: (505) 844-1846 Fax: (505) 845-7442 |
Aerodynamics of a Body Immersed in a Supersonic Wake: A Computational Study
To
determine if a trailing body will remain in the wake of leading body at
supersonic speeds, a computational study was performed to determine the
pressure and streamlines on the surface of the trailing body. In the
picture to the right, the red indicates high pressure on the upper part
of the hemispherical nose, which has been exposed to near freestream
conditions behind the leading body. The cyan on the middle to lower
part of the hemispheical nose indicates low pressure associated with
the recirculation region behind the leading body.
The streamlines on the surface of the trailing body show two rings related to stagnation and separation. The outer ring, indicated by diverging streamlines at the high pressure region, shows the locations of stagnation on the trailing-body surface. The inner ring, indicated by converging streamlines at the low pressure region, shows the locations of separation on the trailing-body surface.
High-Performance Simulations of Coastal and Basin-Scale Ocean Circulation
The
major domestic oil and gas companies are extending their offshore
exploration and production activities into deeper and often
inhospitable waters in search of new reserves. Exploration in these
untapped regions is inherently expensive and can be extremely risky
from economic, environmental, and safety viewpoints. Among other
factors, a significant risk occurs from ocean eddies. Although currents
from persistent eddies may or may not affect a particular drilling
area, conservative safety factors require rig shutdown and possible
abandonment when strong eddies are in the region. Cessation of
activities on rigs, even for short durations, can result in significant
economic losses for typically several companies in the industry per
event. Predicting current surges due to ocean eddies or current-shelf
interactions can reduce the losses incurred by rig shutdown, as well as
aid in deep-water rig design. Thus, accurate and timely predictive
capabilities can widen an oil rig's operational window during pass-by
of ocean eddies. For these reasons, development of high-preformance,
high-resolution predictive capabilities for a basin-scale ocean
environment is warranted.
In the example shown, overset grids are generated around islands and along the shoreline of North, Central, and South America. A background grid helps communicate fluid properties between the various grids. These grids are broken down into smaller grids which can be spread across many processors of a massively parallel computer.
Seismic Imaging on Massively Parallel Computers
A
key to reducing the risks and costs associated with domestic oil and
gas exploration is the ability to image complex geologies, such as
thrusts in mountainous areas and sub-salt structures in the Gulf of
Mexico. Current industry computational capabilities are insufficient
for the widespread application of 3-D, prestack, depth, migration
algorithms. A 3-D data set can be as large as several terabytes in
size, and with current technology, a single image can take months to
produce, and the multiple runs necessary to refine the geological model
may take a year or longer. Oil and gas companies need to be able to
perform complete velocity field refinements in weeks and single
iterations overnight. High performance computers and state-of-the-art
algorithms and software are required to meet this need.
A standard verification step of a migration algorithm is the Marmousi model shown here. The image produced by our 3-D, prestack, depth, migration algorithm, Salvo, has been superimposed over the velocity of the Marmousi model. There is very good agreement between the Salvo image and the velocity model, including the strong reflector at the lower right edge of the image.
Publications:
Last modified: October 12, 1998