The effects of hydrodynamic forces on maneuvrability coefficients for wind-assisted ships

Assessing the manoeuvring performances of a\ua0ship\ua0at a design stage is becoming more important, especially when trying to improve shipping efficiency to reduce fuel consumption. When designing a hull with appendages, it is necessary to balance\ua0hydrodynamic\ua0efficiency with manoeuvrability. Therefore, the possibility of simulating a captive test at a design stage will increase the chances of understanding the behaviour of a\ua0ship\ua0from an early stage in the design process. The current research is based on the evaluation of\ua0hydrodynamic\ua0efficiency of a hull and appendages in a pure resistance, self-propulsion and in a wind-assisted mode. The\ua0forces\ua0and moments acting on the hull and appendages are then analysed and used as inputs for a Virtual Captive Test (VCT) [1]. In order to correctly perform a VCT and further analyse the performances of a\ua0ship\ua0with a Velocity Prediction Programme (VPP), particular care has been put in correctly capturing the manoeuvrability\ua0coefficients. Those are derived with polynomial fittings once the\ua0forces\ua0and moments acting on the\ua0ship\ua0are extracted from the Computational Fluid Dynamics (CFD) simulations. Many CFD simulations were performed to assess the\ua0hydrodynamic\ua0characteristics of the hull and appendages in a range of flow directions, rudder angles and rotating flow. Those simulations encompass the whole range of datapoints needed to describe a wind-assisted\ua0ship\ua0during manoeuvring. Taking into consideration both\ua0hydrodynamic\ua0characteristics and manoeuvrability\ua0effects\ua0at an early design stage can reduce model tests costs and will allow to inspect a larger number of hull-appendages scenarios when analysing the final VPP results