Hansen, J. L.2; v. Hecke, M.2; Haaning, A.2; Ellegaard, C.2; Andersen, Ken Haste3; Bohr, T.4; Sams, Thomas5
1 Technical University of Denmark2 unknown3 National Institute of Aquatic Resources, Technical University of Denmark4 Technical University of Denmark5 Copenhagen Center for Health Technology, Center, Technical University of Denmark
Sand ripples are seen below shallow wavy water and are formed whenever water oscillates over a bed of sand. Here we analyse the instabilities that can upset this perfect patterning when the ripples are subjected to large changes in driving amplitude or frequency, causing them to deform both parallel and transverse to their crests. Our results reveal new pattern-forming instabilities in granular matter exposed to fluid flow with strong vorticity.