Temporally harmonic oscillons in Newtonian fluids

Stationary, highly localized (oscillon) structures are observed in a Newtonian fluid when nonlinear surface waves are parametrically excited with two frequencies. Oscillons have a characteristic structure, that of periodically self-focusing jets. In contrast to previously observed oscillons in highly nonNewtonian media, these states are temporally harmonic with the forcing. For wave amplitudes greater than a critical value, they nucleate from an initial pattern via a hysteretic bifurcation, and can therefore be localized on a background of patterns with a variety of different spatial symmetries.