Non-linear acoustic streaming accompanying a plane stationary wave in a guide

An acoustic standing wave in a guide can generate a significant localised m ean flow: acoustic streaming. A dimensional analysis followed by a perturba tion calculation using asymptotic expansions permits a simplification of th e conservation equations by keeping the leading terms. A time averaging the n leads to equations describing the behaviour of the mean velocity field in a cylindrical waveguide. A noticeable distortion of me field due to the fl uid inertia is demonstrated. This is non-linear streaming, mainly studied f or free or semi-infinite spaces. In the case of a waveguide, the nonlinear effect is determined by an appropriate Reynolds number. A comparison of slo w and nonlinear acoustic streaming is finally presented.