Effects of helicity on Lagrangian and Eulerian time correlations in turbulence

Taylor series expansions of turbulent time correlation functions are applie d to show that although to second order, helicity does not affect Lagrangia n time correlations, the corresponding helicity effect on Eulerian time cor relations is nonzero. This result is applied to two problems in which Euler ian time correlations are relevant: sound radiation and scattering by turbu lence. Helicity shifts radiated sound to lower frequencies and increases th e angle between scattered and incident sound waves. (C) 1999 American Insti tute of Physics. [S1070-6631(99)01108-3].