Enhanced CFD capabilities put AEDC on cutting edge

  • Published
  • By Shawn Jacobs
  • AEDC/PA
ARNOLD AIR FORCE BASE, Tenn. --  Computational fluid dynamics (CFD) has been around for years now, but recent advances in hardware and computer codes are helping make Arnold Engineering Development Center (AEDC) among the leaders in this scientific field.

Dr. Ralph Jones, branch manager of Aerospace Testing Alliance's (ATA) Technology Analysis Branch, described CFD as a technique for simulating the flow of fluids. ATA is the operating contractor for AEDC.

"We deal with lots of fluids around the base, but we're principally interested in air," he said. "There are some rather complex equations that describe how fluids move ─ either
over bodies like airplane models, wings, things of that nature ─ or internal to systems such as facility ducting, nozzles and turbine engines. There are mathematical techniques that allow you to approximate the equations and come up with solutions that are highly representative of the flow field of interest."

In a sense, running a CFD code is analogous to running a test in one of AEDC's facilities. CFD's equivalent of a test cell is a supercomputer with large memory and fast
processors on which scientists can run the software tools and codes that are developed, Dr. Jones said.

But CFD can be "wider" than just the wind tunnels, according to Tracy Donegan, section head in the Technology Branch, who is involved in the development of new efforts and application of capabilities. "It could be expanded looking beyond just air," he said. "One of the primary areas is air calculations over bodies, but then you get into more complex calculations where you start computing chemistry and combustion effects - turbine engines and so forth - which make simulations much more complicated."

Many recent CFD enhancements actually involve computer code and interagency cooperation, according to Dr. Greg Power, ATA technical fellow for computational modeling and simulation. "Our goal is to have production capabilities ready to support the wind tunnels and to support the warfighter in general," he said. "We get those tools from a lot of different sources."

AEDC uses available government tools, as well as those developed at NASA and some industrial and commercial tools. "Many times the software that we have available can't handle the problems that we're faced with, so we're a lot of times at the leading edge of the types of problems that we need to handle," Dr. Power said. "We have to develop our own capabilities, more times than not, in concert with other folks within government and the Air Force Materiel Command (AFMC)."

Dr. Power said AEDC's CFD program has a close relationship with the Air Force SEEK EAGLE Office (AFSEO) at Eglin AFB, whose goal is to improve the combat capability of the warfighter. The SEEK EAGLE Program is the standard for the aircraft-stores certification process of the Air Force.

Other CFD enhancements are the result of hardware acquisition and development.

"The High Performance Computing Modernization Office has provided a lot of funding for us over the past 10 years to do development, and not only helping us by providing the
hardware that we use, but they also provide us funding for development," Dr. Power said. "We've been developing, over the years, capabilities to enhance the ability to do store separation simulations, such as dropping weapons or fuel tanks or firing missiles.

"Now we're much more multidisciplinary; you have multiple bodies interacting with one another, but you also need to have the ability to address aero structural phenomena so the wings are deforming. We're developing that capability in concert with others."

Turnaround time is another factor that has improved dramatically in CFD testing.

"The advancements in both complexity and reductions in turnaround time ... have come from both software improvements, physical model improvements and computer capability," Dr. Jones said. "Literally thousands of times improvement in capability for doing external aerodynamic computations [have been realized]."

In the area of verification, Donegan said they have an extensive suite of simulations that can be used to validate codes. "They may range from just very simple problems to
which we know the answer to fairly complex problems that we've done before that we have extensive data from say a wind tunnel," he said. "Our goal isn't to diminish wind tunnel testing but to augment it such that we have a more effective program, which often can save the customer money."

On the Air Force side of the operation, Dr. Terrance Dubreus is an aerospace engineer/program manager for the modeling and simulation capability with the Test Technology Branch. He agreed the future is bright for CFD advances at AEDC.

"Our modeling and simulation engineers are world class with a long history of applying their expertise throughout the Department of Defense (DoD) and NASA," he said. "In the years to come we will continue to leverage new technologies, hardware and software, to further the DoD mission."