Vortex Identification Methods Applied to Complex Viscous Flow Field of Ship in Restricted Waters

Abstract

Vortex plays a vital role in the generation and maintenance of turbulence. The flow mechanism around the ship and marine structures can be deeply analyzed through the vortex structure, which is of great significance to the study of turbulence problems. The performance of ships in restricted waters is much different from ships in open waters. The issue of the ship entering a lock is one of the most typical situations of the restricted waters. In this paper, different generations of vortex identification methods are applied to complex viscous flow field of an 8,000t bulk carrier entering a lock. The turbulent flows are modeled by Reynolds averaged Navier–Stokes (RANS) simulations based on the two-equation k-ω shear stress transport (SST) model. With the help of the overset grid method, the surface pressure of the ship, wave height of the free surface and the wave field are analyzed numerically to explain the ship hydrodynamic performance. Then, based on Liutex vortex identification, the vortex structures in the viscous flow field are captured. Compared with the traditional vortex identification methods, the third-generation methods show a better ability of capturing the vortex structures and gives a more accurate definition of vortex, which can be used in the study focused on the flow mechanism, especially on the problem of the ship-lock interaction. All the analysis aspects of the flow field in this work above provide a reference for the post-processing method of the complex viscous flow field of ship in restricted waters.