EXPERIMENTAL STUDY ON THE VIBRATION CHARACTERISTICS OF RISER UNDER GAS-LIQUID TWO-PHASE FLOW BASED ON DAS

The pipeline pneumatic conveying system, as a green and environmentally friendly transport system, has huge potential for application in the development of marine resources and energy. However, due to its involvement in complex pipeline gas-liquid/gas-liquid-solid multiphase flow, there is a lack of relevant theoretical foundations, monitoring methods, and analytical techniques, which greatly limits its engineering application. This study uses distributed acoustic sensing (DAS) technology to collect the vibration signals of risers under different submergence ratios and gas flow rates. The results show that the amplitude of the riser vibration signals increases with the gas flow rate, reaching a peak value of 0.227 rad during Churn-Annular flow. Under the same gas flow rate, the vibration intensity of the riser is strongest when the submergence ratios are 0.8 and 0.85. Energy ratio analysis of the signals reveals that the 0-20 Hz and 20-40 Hz frequency bands account for the main part of the riser vibration energy, with the 0-20 Hz band reaching the maximum energy ratio of 80% during Churn-Annular flow. This study provides a feasible research method for using optical fiber technology to carry out health monitoring and engineering applications of the pipeline pneumatic conveying system.