Numerical study on the forces and moments on a bottom-mounted cylinder by internal solitary wave

Abstract

The forces and moments on a bottom-mounted cylinder by internal solitary wave are investigated with numerical simulation. The solution of Dubreil–Jacotin–Long equation is used to initialize internal solitary wave in the computational domain, which overcomes the deficiencies of internal solitary wave generated by gravity collapse method. The continuous density stratification is taken into account in this study and numerical results show that the shape of pycnocline could influence the forces and moments exerted on cylinder by internal solitary wave. The forces and moments on different cylinder sections are calculated separately, the derived forces exhibit similar patterns observed in previous laboratory measurements. The results show that the loads by internal solitary wave on cylinder are quite complex as the wave induced velocity field is unsteady and the directions are opposite between upper and lower layers. The performance of Morison equation is examined and three coefficient determination methods are tested, force based global coefficients, moment based global coefficients and local coefficients. The analysis shows that the global coefficients are sensitive to the data adopted, which explains why universal coefficients are not available from previous studies.