eugene@ames.UUCP (Eugene Miya) (02/07/85)
Some of our physicists are tired of having insufficient computer power
(A Cray-XMP is 1/1000 of what they want), so some of them posted this
note on a board:
WILL THE WIND TUNNEL REPLACE THE COMPUTER
We all know of the importance of computers in today's aerospace engineering
environment. The latest advances in cryogenically cooled semi-superconductor
technology and microscopic germanium sub-wafer assembly has made desktop 100
MINS (Millions of Navier-Stokes solutions) machines commonplace in engineering
use.
We are also aware, however, of the high cost of this aging technology. The
most accurate aerodynamic prediction code available today, FLO-1234.5, is so
complex and expensive that it has never been run. Many other codes, if run to
completion, would require CPU time exceeding the average human lifespan. Most
engineers attribute this situation to the time when the task of writing
aerodynamic computer programs was automated and handed over to the computers.
We now have codes too complex to be understood by any human being. The cost
of computing has been rising exponentially over the years. Clearly, if these
trends continue unabated, computational solutions will soon be beyond anyone's
means.
Fortunately, there is an exciting new technology on the horizon which may
someday replace the computer for aerodynamic design and analysis. Two workers
at UNCAF (United Nations Computational Aerodynamics Facility) have recently
made a startling discovery. They found that by building a small wooden model
of an airplane and then blowing air past it in an enclosed tunnel, reasonably
accurate predictions may be made of what the flow codes would compute. They
refer to the method they have discovered as a "wind tunnel". At present,
"wind tunnel" modeling is still in an early and relatively crude stage, and
cannot be expected to precisely reproduce numerical results. For example, the
continuous surface of a wood or metal airplane model will never exactly
duplicate the discrete nature of a computational grid. Also, some reproduce
numerical results. For example, the continuous surface of a wood or metal
airplane model will never exactly duplicate the discrete nature of a
computational grid. Also, some factors, such as artificial viscosity, are
neglected completely in wind tunnel modeling. It may be especially hard to
accurately predict linearized potential flow in the tunnel. Nevertheless, in
many cases, the wind tunnel agrees surprisingly well with the computer.
Constructing a wind tunnel model is much quicker and less labor-intensive than
running all but the simplest computer programs. Shops such as Minicraft or
Static Engineering complete even a highly detailed titanium model in a mere
matter of months. Thus, many design iterations and trade-off studies can be
conducted in a fraction of the time required via the computer. Advances in
wind tunnel technology and model fabrication are expected to proceed at a
rapid pace. Many promising new techniques, such as the chiseling of facets in
Plaster-of-Paris models to more closely resemble computational panelings and
grids, are already being suggested by researchers around the world. The
future prospects of this amazing new wind tunnel technology are bounded only
by the imagination.
But what, you may ask, will be the fate of the millions of computational
aerodynamicists presently employed in the aerospace industry? Is the wind
tunnel a threat to their job security? While it is true that some may lose
their jobs, a brand-new demand will be created for those well-versed in
state-of-the-art wind tunnel technology. Engineering graduate schools are
already replacing course offerings in Finite Volume Methods and Grid
Generation with curricula in Woodworking and Whittling. Clearly, the engineer
will be freed from the tyranny and drudgery of computational methods, giving
him more time to concentrate on creative tasks. It is doubtful, however, that
the computer will ever be completely eliminated; the thought of an airplane
designed solely from wind tunnel data without the aid of the computer seems
too incredible to believe. While the wind tunnel may never fully replace the
computer, it is almost certain to become the most useful engineering tool of
the future.
NASA Ames 1984