Elastic Wave Propagation Characteristics Of The Structure Of Long-distance Cycle Tube

Long pipelines serve as a channel not only delivering mass but transmitting information, which play an important role in industries. The problem is a very challenging research area, which employing the pipe wall as the transmission channel of the data telemetry or malfunction alarm systems. Based on the periodical pipelines such as the drill strings and oil pipe, the transmission properties of elastic wave in pipe wall are systematically studied.Firstly, the characteristic and mechanics of elastic waves in solid, especially the long slender rod with uniform circular cross-section, is analyzed. The longitudinal wave is considered as acoustical carrier waves of the logging method, and its feasibility is examined preliminarily.Secondly, the dispersion equation of longitudinal wave is derived based on the transmission model that longitudinal waves propagate along the periodic structure such as the drill strings or oil pipe. Frequency-domain analysis is made using the dispersion curves. It is shown that the pass bands and stop bands appear alternately for the longitudinal transmission waves in the frequency domain, and the distribution of frequency spectrum exhibits periodic and symmetrical property; the phase velocity and group velocity are the function of frequencies in the pass bands; the length of the drill pipe or the area of the joints has great influences on the spectrums.Finally, experiments are made with the finite length oil pipe. It is shown that the theoretical results are very close to the experiment results, thus verifying the reliability of the above theoretical model.