On the distinction of axisymmetric waves within a fluid-filled pipe using wavenumber measurement

Axisymmetric waves have characteristics, which are of practical interest when assessing the condition of a buried plastic water pipe. At low frequencies, well below the ring frequency, these waves are dominant. They are well couple to the fluid, pipe wall and surrounding medium and carry a high amount of energy when compared to other waves. Due to substantial differences in the wavenumber of the s=1,2waves a new experimental method has been developed to distinguish between the pipe wall motion that arises from each axisymmetric wave. The results from experimental studies are compared with the theoretical predictions and a good agreement has been found. The outcomes of this investigation clarify the characteristics of the dominant axisymmetric wave within the buried pipes and thereby the waves generated within the surrounding medium. Moreover, decomposition of the two waves will help quantify the value of pressure within the fluid. Further application of this distinction is interpretation of the characteristics of the excitation source.