WILL THE WIND TUNNEL REPLACE THE COMPUTER?
A spoof from the late seventies, from Peter Knott -
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 ageing 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 a 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 aeroplane 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" modelling 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 aeroplane 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 modelling. It may be especially hard to accurately predict linearised 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 labour-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 chiselling of facets in plaster-of-paris models to more closely resemble computational panellings 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 aeroplane 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.