A steady horizontal air stream flows across a book [1,2] clamped at its downstream end. Pages lift off to form a growing bent stack whose shape is determined by the torques associated with aerodynamic forces, weight and elastic resistance to bending. As more pages lift off to join the bent stack, the increasing importance of bending rigidity to dynamic pressure eventually causes the book to clap shut. The process restarts, and self-sustained oscillations emerge.

[1] M. van Dyke, An Album of Fluid Motion (Parabolic Press, 1982). [2] M. Samimy, K. S. Breuer, L. G. Leal, P. H. Steen, A Gallery of Fluid Motion (Cambridge University Press, 2003).