Experimental numerical study of natural vibrations of steel pipe with internal water flow

The paper presents an experimental and numerical investigation of the natural vibrations of a horizontal steel-pipe section 8 m long with an internal diameter of 180 mm and a wall thickness of 10 mm, while pressurised water is circulating through it. Vibrations were recorded with a piezoelectric accelerometer mounted on the pipe surface, and the signals were subjected to spectral analysis in the LGraph software suite. In the frequency range up to 53 kHz a steady resonant peak attributable to one of the pipe’s bending modes was detected. To interpret the results, a mathematical model based on Euler–Bernoulli beam theory was developed. The model predicts the frequency of the first higher-order bending mode to be 2.95 kHz, which differs from the experimental value by less than 3 %. The practical applicability of the results for vibration monitoring is demonstrated: shifts in natural frequencies can serve as sensitive indicators of leaks or structural defects, especially when combined with remote radar methods. The findings provide a foundation for the development of an integrated pipeline-condition-monitoring system that couples mathematical forecasting with highly sensitive field measurements.