Investigation of non-linear acoustic losses at the open end of a tube

At high acoustic level, non-linear losses at the end of a tube are usually interpreted as the consequence of a jet formation at the tube end resulting in annular vortices dissipating part of the acoustic energy. Previous work has shown that two different regimes may occur. The present work, using particle image velocimetry visualization, lattice Boltzmann method simulation in 2D, and an analytical model, shows that the two different regimes correspond to situations for which the annular vortices remain attached to the tube (low acoustic particle velocity) or detached (high acoustic particle velocity). (C) 2011 Acoustical Society of America. [DOI: 10.1121/1.3543987]