Abstract
This article presents a detailed numerical flow assessment of the boundary layer and wake of a full-scale cargo ship. The assessment was conducted using a sophisticated numerical approach that is able to resolve large turbulent scale vortices contained in the flow. The physical flow features of the boundary layer and wake investigated include mean-velocity, near-wall shear stress and vorticity fields. Also, the evolution of the wake from the thick boundary layer over the stern is displayed and analysed in the highest possible detail. Additionally, the detailed information extracted from the boundary layer and wake was the primary input to assess the overall hydrodynamic efficiency of the full-scale general cargo ship.The analysis method followed during this work has been a determinant factor for fast and efficient design of energy saving devices, propellers or rudders that work within the limits of the boundary layer of a ship. In particular, this thorough analysis avoided the necessity to use the commonly used practice of trial and error that is typically followed in the maritime industry.
Highlights
Experimental fluid dynamics towing tank tests have been traditionally used to evaluate the flow around the ship
The assessment was conducted using an Improved Delayed Detached Eddy Simulation (IDDES) sophisticated numerical approach able to directly resolve from the Navier-Stokes equations any relatively large turbulent scale vortices contained in the flow
Ship resistance per unit length measurements and pressure coefficient distribution confirmed a pressure resistance coefficient imbalance between the aft and fore end of the ship. This resistance imbalance resulted in an increased pressure drag being the main source of a less than optimum hydrodynamic efficiency for the given geometry
Summary
Experimental fluid dynamics towing tank tests have been traditionally used to evaluate the flow around the ship. An alternative method to assess the near-wall flow of the ship relies on viscous flow Computational Fluid Dynamics (CFD) It is based on the Navier-Stokes equations and allows numerical modelling of scenarios in full-scale, avoiding scaling issues. A most recent approach for the simulation of turbulent ship flows is based on a combination of RANS/LES, such as DES (Detached Eddy Simulation) This method combines the best features of LES and RANS by only using LES away from the wall where a high level of unsteadiness of the flow is expected (i.e. around the bilges, detached flow regions or in the wake) while RANS is applied in the near-wall region. Resistance distribution and velocity fields have been post-processed to assess the hydrodynamic performance of the 'MV Regal' (Lloyds Register, 2016), a full-scale general cargo ship
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