Shape of things to comeFlexible, flapping flying machines may be on the horizon
Rigid wings and rotors have made aircraft very successful; nature, however, prefers flexible, flapping flying structures — just look at birds; indeed, the most efficient and acrobatic airfoils in nature are the flexible wings of the bat; Brown University researchers want to adopt the bat’s approach to flying for human use
Modern aircraft have been very successful with rigid wings and rotors. Imagine, though, the flying machines which would be possible if we could understand and harness the most efficient and acrobatic airfoils in nature: the flexible wings of the bat. The aerodynamics of “compliant” structures, such as bat wings, are complicated because both the structure and airflow change and adapt to each other in a highly nonlinear way. Bats’ wing bones are even flexible, unlike those of birds, which gives the mammals added control but is an additional challenge for scientists trying to understand them.
Kenny Breuer’s research group at Brown University is designing a series of fundamental experiments which will allow scientists to isolate, observe, and analyze a variety of specific flow-structure interactions that are important in understanding bat flight and, in general, the aerodynamics of compliant structures. Ultimately, Breuer expects that experiments like these will yield insights enabling new generations of flying machines that are impossible to consider today.
In his talk at the 61st Annual Meeting of the APS Division of Fluid Dynamics in San Antonio, Arnold Song, who is one member of this research group, will describe the basic motions — and their aerodynamic implications — that he and his colleagues at Brown have discovered so far by measuring how paddles and stretched ribbons of sailcloth vibrate in man made breezes in a wind tunnel. As the airflow increases, for example, a paddle on a post first twists and then flaps, as a stop sign being pummeled by hurricane-force winds would. The ribbon’s behavior is more complicated, but also essential for understanding how bat wings or other compliant structures generate lift so efficiently.
-read more in Arnold Song et al., “Vortex Induced Motion in Compliant Structures” (paper to be presented at the 61st annual meeting of the American Physical Society Division of Fluid Dynamics, San Antonio, Texas, 23 November 2008)
