To the theory of acoustic scanning of pipelines with the damaged areas

The evolution of the pressure disturbances propagating in the tubular channel filled with liquid or gas and having a damaged portion in a sufficiently large gaps with low resistance. To this end, it adopted a mathematical model that takes into account the viscous friction and heat transfer in a thin layer of liquid (or gas) near the wall. On the basis of this model, dispersion equation for distribution processes and reflections from the damaged portion of harmonic waves. The dependence of the phase velocity, attenuation coefficient, as well as the reflection and transmission coefficients of the angular frequency and the physical properties of a liquid or gas. The results of calculations to illustrate the dynamics of pulse signals depending on the magnitude of damage, defined as the ratio of the gap area to the sectional area of the channel.