Acoustic Wave Propagation in Water Filled Buried Polyethylene Pipes

Axisymmetric acoustic wave-modes propagating along buried water pipes have been investigated by the method of finite elements and experimentally. High precision dispersion relations are presented in this paper as a function of the geometry, the embedding material and the elastic modulus of the pipes. It is found that at low frequencies the fundamental axisymmetric acoustic mode of the water cylinder is nearly a plane wave. This mode is the dominant component of a leak noise signal propagating along the pipe. At moderate frequencies the acoustic pressure is small in the centre of the water column and builds up close to the wall of the pipe, inside and outside the elastic pipe layer. Attenuation at moderate frequencies is not substantial. At high frequencies an additional mode emerges in the water cylinder, driven by the wave in the elastic pipe wall.