title: Acoustic second harmonic generation from rough surfaces under shear excitation in liquids.
abstract: Emission of compressional acoustic waves at the second harmonic frequency (second harmonic generation, SHG) is possible from rough surfaces undergoing oscillatory shear in liquids. This nonlinear response is a consequence of the inertial term in the Navier-Stokes equation. On a corrugated surface, the streamlines of the sheared liquid are not strictly parallel to the surface, leading to variation of pressure along the streamlines and a concomitant Bernoulli pressure. Being quadratic in speed, the Bernoulli pressure contains a static term and a term at the second harmonic frequency, 2omega. Pressure fluctuations at 2omega generate compressional waves.
authors.affiliation: Institute of Physical Chemistry, Clausthal University of Technology, Arnold-Sommerfeld-Str. 4, D-38678 Clausthal-Zellerfeld, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Wondraczek
authors.forename: Andreas
authors.initials: A
authors.lastname: Bund
authors.forename: Diethelm
authors.initials: D
authors.lastname: Johannsmann