Abstract

In this study we investigate the formation and characteristics of ship wakes – the V-shaped traces that form behind moving objects in water. They were first theoretically explained by Lord Kelvin in 1887, who proposed that all ship wakes have a constant angle, independent of any of the ship’s parameters, now known as the Kelvin wake angle.

In recent years this long-standing model has been questioned –  scientists were looking at satelite images of ships and they observed wake angles much smaller than the Kelvin one. However, this has not been experimentally investigated, nor has there been a universal theoretical model that could explain both the narrow and the Kelvin angles. By conducting experiments with a drone and a boat, satelite image analysis and a small-scale experimental setup, we obtained both the classical and the narrow wake angle regimes.

Our novel theoretical model is in better agreement with experimental data. This is especially true for boats with a high Froude number, meaning the boat has a short length but travels with a high velocity. The improved predictions of the angle can benefit marine simulation software, simplify the ship design prosses and even help with fuel optimisation. Our model is superior in the transition region between the Kelvin and the narrow wake angle regime. For higher Froude numbers, our model is very close to the best narrow angle model so far, and for lower values it simplifies to the classical Kelvin wake angle, proving that our theory is more universal than previously established models.