Investigation on the periodically oscillating pressure characteristics of the flow in the rolling pipe

The floating LNG plants are gaining recently increasing attention in offshore energy exploitation. The effects of periodically oscillatory motion on the fluid flow in all processes on the offshore plant are very complicated and required detailed thermodynamic and hydrodynamic analyses. In this paper, numerical simulations are conducted by CFD code combined with user-defined functions (UDF). The computational model of the circular pipe flow is established with the excitation rolling motion, at the excitation frequencies of 1–4 rad/s and the excitation angles of 3–15 degree, respectively. The influences of the flow velocities and excitation conditions on the pressure characteristics, including the time-average pressure, the amplitude and the period of pressure fluctuation are systematically investigated. It is found that the pressure fluctuation of the in-viscid flow keeps almost constant at different flow velocities. The amplitude of the pressure fluctuation increases with the increase of the excitation angle. Meanwhile, with the increase of the excitation frequency, the amplitude decreases in the vertical pipe, but increases in the horizontal pipe. It is also found that the period of the pressure fluctuation is depended on the excitation frequency. Furthermore, the theoretical analyses for the flow in the rolling circular pipe are conducted, which qualitatively agree with the numerical simulations.

► The flow in rolling pipe is numerically simulated and theoretically analyzed.
► The pressure fluctuation of in-viscid flow varies slightly with the flow velocity.
► Amplitude of the pressure fluctuation increases with the excitation angle.
► Effect of the excitation frequency is different in vertical and horizontal pipe.