2-DIMENSIONAL ANGLE-OF-ARRIVAL FLUCTUATIONS

Angle of arrival fluctuations are one manifestation of acoustic propag ation through a turbulent flow. Here the two-dimensional angle of arri val distribution for a 670-m acoustic path through a high Reynolds num ber flow in a tidal channel is examined and its origin and relationshi p to the flow field is determined. Over scales greater than the variab ility due to turbulence, a solution of the ray propagation equation ex plains the effect of advection on the horizontal arrival angle. The ra pidly fluctuating two-dimensional angle of arrival distribution shows a degree of scatter consistent with the level of turbulent intensity. After removal of effects due to the finite aperture, orthogonal compon ents are correlated during strongly sheared flow implying that the tur bulence is weakly anisotropic over the measured scales. This anisotrop y is discussed in terms of the cross stream velocity gradients partial derivative v/partial derivative x' and partial derivative v/partial d erivative z', where (x',z') are perpendicular diagonal coordinates. (C ) 1996 Acoustical Society of America.