Abstract
While designing the power requirements of a ship, the most important factor to be considered is the ship resistance, or the sea drag forces acting on the ship. It is important to have an estimate of the ship resistance while designing the propulsion system since the power required to overcome the sea drag forces contribute to ‘losses’ in the propulsion system. There are three main methods to calculate ship resistance: Statistical methods like the Holtrop-Mennen (HM) method, numerical analysis or CFD (Computational Fluid Dynamics) simulations, and model testing, i.e. scaled model tests in towing tanks. At the start of the design stage, when only basic ship parameters are available, only statistical models like the HM method can be used. Numerical analysis/ CFD simulations and model tests can be performed only when the complete 3D design of the ship is completed. The present paper aims at predicting the calm water ship resistance using CFD simulations, using the Flow-3D software package. A case study of a roll-on/roll-off passenger (RoPax) ferry was investigated. Ship resistance was calculated at various ship speeds. Since the mesh affects the results in any CFD simulation, multiple meshes were used to check the mesh sensitivity. The results from the simulations were compared with the estimate from the HM method. The results from simulations agreed well with the HM method for low ship speeds. The difference in the results was considerably high compared to the HM method for higher ship speeds. The capability of Flow-3D to perform ship resistance analysis was demonstrated.
Highlights
It is important to confirm the performance characteristics of a ship before construction because of the complexities and high costs involved in construction [1]
Ship resistance is one of the performance characteristics and is defined as the force required to overcome the hydrodynamic and air resistance that works against its movement
This paper presents a procedure for CFD simulations to calculate the calm water ship resistance with a case study of a roll-on/roll-off passenger (RoPax) ferry
Summary
It is important to confirm the performance characteristics of a ship before construction because of the complexities and high costs involved in construction [1]. There is a significant environmental impact of such high volumes of shipping and it can be considered as a major contributor to climate change [4] It is an aim for ship designers to minimize ship resistance. It is an extremely useful tool to estimate ship resistance in early stages of the ship design process. CFD analysis is becoming the preferred method over model tests for calculating ship resistance due to availability of powerful computational resources and advancements in the field of CFD [7]. It was observed that the results for ship resistance from the CFD simulations confirm well with the calculations with the HM method at lower ship speeds. Holtrop and G.G.J. Mennen in 1982 proposed a method to predict ship resistance and power requirements at an early design stage. Details regarding the calculations involved in the HM method are not divulged and the results are presented directly
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