Speed loss of a vessel sailing in oblique waves

In order to demonstrate the effect of oblique waves on ocean-going vessel behavior in realistic sea states, this paper addresses an effective and useful tool to predict the ship's motion and propulsion system behavior with sufficient accuracy, considering the wave conditions on the operating route. Seakeeping model test was carried out with a freely running model in oblique waves in the ocean basin at the Marine Technology Centre, Trondheim, Norway. A time domain numerical simulation study was performed, and the results of the simulation are compared with the model test data.Due to the length limitation of the ocean basin, converged speed in waves cannot be achieved in all runs. A correction method is proposed in this paper to determine the converged speed from non-converged runs. The correction method is based on the condition that the converged speed in waves is dependent on the balance between resistance and propulsion force.

► Ship's speed loss in oblique waves and azimuth propulsor behavior were studied.
► Seakeeping and maneuvering model tests with a freely running model were done.
► Attainable speed prediction method was proposed based on non-converged runs.
► Numerical simulations were conducted to predict speed loss in oblique seas.
► Speed loss due to added wave resistance and due to steering is figured out.