PROPAGATION IN A LIQUID LAYER LYING OVER A LIQUID HALF-SPACE (PEKERIS CUT)

Sound propagation in a uniform duct can be represented as a sum of normal modes plus a branch line integral(s) contribution. In the case of a homogeneous liquid layer lying over a homogeneous liquid half-space the complex modes exhibit a complicated migration as frequency is changed. In the case of a Pekeris branch cut this can result in the mode changing from a proper to an improper Riemann sheet or vice versa. This is accompanied by a discontinuous change in the branch line integral. This paper examines the migration of a typical mode and discusses a simple algorithm for calculating the Pekeris branch line integral. © 1979, Acoustical Society of America. All rights reserved.