  Small flexible fibers in a turbulent flow are found to be most of the time as
straight as stiff rods. This is due to the cooperative action of flexural
rigidity and fluid stretching. However, fibers might bend and buckle when they
tumble and experience a strong-enough local compressive shear. Such events are
similar to an activation process, where the role of temperature is played by
the inverse of Young's modulus. Numerical simulations show that buckling occurs
very intermittently in time. This results from unexpected long-range Lagrangian
correlations of the turbulent shear.
