Roll waves on flowing cornstarch

A cornstarch and water solution flowing down an incline goes unstable to a field of roll waves.

We report a traveling wave instability in low Reynolds number flows of aqueous concentrated suspensions of corn starch. The experimental observations are difficult to reconcile with theoretical predictions based on simple rheological models which indicate that flows are stable at low Reynolds number.

See paper here: Balmforth, Bush & Craster (2005)