7. Unsteady Aerodynamics

Man’s dream of flight became a reality when the Wright brothers lifted off in their first flyer in 1903. During the subsequent 100 years, advancements in manned flying machines were amazingly rapid. The speed, flight range and height achievable with modern airplanes far exceed those of the birds whose flights inspired mankind since ancient times. With air travel so commonplace today, the flying public generally deems aerodynamics a mature discipline of science. The popular view is that all major discoveries in aerodynamics were made long before the end of the past century. The remaining tasks today are not so much the search for improved physical understanding, but the collection of additional aerodynamic data for design refinements, tasks that require mostly testing and computation. It is informative, however, to pause a moment and review briefly a fundamental concept of aerodynamics based on which manned flying machines were designed and built—the idea of streamlined steady flows around fixed wings—and to compare the flights of these machines with those of birds.