HIGH-WAVENUMBER ACOUSTIC RADIATION FROM A THIN-WALLED AXISYMMETRIC CYLINDER

The radiation from an axisymmetric thin-walled cylinder is determined by using the Geometrical Theory of Diffraction. The non-uniformities associated with this theory are corrected by using uniform asymptotic techniques, and the farfield velocity potential is calculated everywhere. The theory provides a paradigm for interpretation of geometrical features of the directivity pattern in the far field, and the results are discussed from this perspective. Comparison is made with analytical results obtained by using the Wiener–Hopf technique and the agreement is shown to be excellent. In particular, the uniform asymptotic techniques give the correct farfield form of the velocity potential in the principal lobe and predict the value at the peak of the principal lobe very accurately. This work provides a theoretical basis for the investigation of the radiation from asymmetric cylinder apertures, which has important applications in the noise reduction of aircraft, and which is discussed in a companion paper.