ACOUSTIC RADIATION FROM 2 OPPOSED SEMIINFINITE COAXIAL CYLINDRICAL WAVE-GUIDES .2. SEPARATED DUCTS

The radiation of sound waves from two coaxial circular cylindrical wav eguides is discussed in this article. Both ducts are semi-infinite in length, one extending from Z = l to Z = -infinity and the other from Z = 0 to Z = +infinity, where z is a coordinate measured along the cyli nders' axis. Waves are incident from z = -infinity inside the smaller radius duct and the reflected, transmitted and radiated fields are cal culated here for the case when the waveguides are separated by a gap o f arbitrary length \l\ (l < 0). In the first part of this study (Lawri e et al., Wave Motion 18, 121-142 (1993)) the model was solved for ove rlapping pipes l > 0 by reducing the problem to a matrix Wiener-Hopf e quation, which was solved by the introduction of an infinite constant vector satisfying a simple algebraic system of equations. This procedu re does not follow through for the case of a gap, due to the presence of exponentially growing elements, and further analysis is required to solve for the Wiener-Hopf unknowns. Numerical results are presented h ere for a range of values of gap length and duct radii.