In order to explore the influence of the free surface and free end on the flow field around typical bluff bodies, the flow field around a finite-length cylinder with a free surface is studied.

Based on the delay detached-eddy simulation (DDES) approach and piecewise linear interface calculation (PLIC) method, our in-house solver naoe-FOAM-SJTU is adopted to carry out numerical simulations.

The results show that the existence of the free surface and free end increases the lift and drag of local positions, and delays the occurrence of flow separation on the cylinder's surface. Compared with the deep draft region, the recovery of streamwise velocity near the free surface is delayed, and the transverse velocity tends to move outward. The deformation of the free surface generates many small vortices, and the twisted vortex at the free end restrains the development of the Kármán vortex street to a certain extent.

This study shows that the current numerical methods can accurately capture this complex flow field. At the same time, the existence of the free surface and free end significantly changes the distribution of the flow field in the draft direction.