Acoustical wave propagation in buried water filled pipes

Abstract

This thesis presents a comprehensive way of dealing with the problem of acoustical wave propagation in cylindrically layered media with a specific application in water-filled underground pipes. The problem is studied in two stages: First the pipe is considered to be very stiff in relation to the contained fluid and then the stiffness of the pipe and the soil are taken into account. In both cases the solution process can take into account signals of any form, generated in any point inside the pipe. The simplified method provides the basic understanding on wave propagation and noise generation in the pipe in relation to pipe radius and frequency of excitation. Following the simplified analysis, the beam forming method is discussed and applied in order to reduce the noise in the pipe. Moving on to the complete analysis of the pipe, the stiffness matrix method is used to take into account the properties of the system. The solution time is proven to be much higher in this case, but the results vary from the simplified case in many real value problems. The results of the two methods are compared in more detail and then a decision making process for the choice of method is developed. This decision process is based on the frequency of the excitation, the properties of the materials and the dimensions of the system.