Assessment of Methods for Calculating Liquefied Natural Gas Pump Tower Loads

Abstract

This paper presents a comparative numerical study on liquefied natural gas (LNG) pump tower loads, while focusing on two aspects. First, are impact loads relevant for the structural design of LNG pump towers and, second, in which way does fluid–structure interaction influence these loads? Numerical simulations of the multiphase problem were conducted using viscous field methods. First, unsteady Reynolds-averaged Navier–Stokes (URANS) equations, extended by the volume of fluid (VoF) approach, were used to simulate, at model scale, the flow inside a three-dimensional LNG tank without the tower structure. Then, these results were used to validate the numerical method against model test measurements. Afterward, motion periods and amplitudes were systematically varied in the flow simulations. Flow velocities and accelerations along the positions of the main structural members of the pump tower were extracted and used as input data for load approximations based on the Morison equation. Finally, these load approximations were compared with loads determined from solving the delayed detached eddy simulation (DDES). Time histories as well as statistical measures of global loads acting on the entire and the simplified tower structure were of the same order of magnitude. However, their time evolution differed, especially at their peaks, and this was considered significant for structural design.