CFD Investigation into the Wave Added Resistance of Two Ships

Abstract

In optimising a ship design for a reliable operational performance, it is important to obtain, in an early design stage, an accurate estimate of the resistance and propulsion characteristics in calm water as well as in the wave conditions encountered service. In this process CFD has become quite mature in quantifying the frictional and pressure drag in the calm water. In waves, CFD simulations are still less time efficient compared to potential flow methods which are still indispensable in covering large operational condition matrices required for a complete assessment of the operational performance.

The above problem does not mean that a CFD assessment of the added resistance is not relevant. As is shown in the present work, it offers quite important insight in the nature of the added resistance in waves, which offers a direct hint on ways to improve the hull form. A very important result of the present work is that it demonstrates that the traditionally assumed quadratic relationship between the wave amplitude and the added resistance is only partly valid. For both ships under consideration, CFD results as well as the results of experiments show a clear relative decrease in higher waves.

The above observations are based on a CFD analysis and experiments for two hull forms sailing in head waves. The two subject vessels are the parent hull form of the Fast Displacement Ship series (FDS), and the Kriso Container Ship (KCS).

The CFD calculations are performed with the URANS code ReFRESCO. The grid generation and solution method are described in detail and the convergence of the results is given adequate attention. The obtained heave and pitch RAOs and the added resistance are compared against calculations performed with the Rankine source potential flow solver FATIMA and results of dedicated experiments in MARIN’s Seakeeping and Manoeuvring Basin.

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