When a ship travels on the water's surface and experiences a phenomenon where its speed decreases or even comes to a halt due to the presence of internal waves, it is referred to as the “dead water effect.” This phenomenon is most common during early spring, when winter ice is melting, and in areas like river estuaries that are prone to stable density stratification. This study primarily investigates the “dead water effect” by creating density stratification using saltwater in a water tank and simulating real-life scenarios with a model ship to understand the relationship between internal waves and the dead water effect.
The results indicate that the occurrence of a severe dead water effect is more likely when the tension is lower, the ship's weight is higher, the upper water layer is thinner, and the lower water layer is thicker. Regardless of the ship's speed, the influence of internal waves is observed when the Froude number approaches 1, resulting in a deceleration. When the acceleration becomes negative, it is referred to as the dead water effect. Once a ship experiences the dead water effect and accelerates again, the ship's wake enhances the residual waves, leading to a possible reoccurrence of the dead water effect, causing the Froude number to oscillate around 1. Complete escape from the dead water effect is only possible when the internal waves break or when the stratification becomes chaotic. Furthermore, this study has found a relationship between ship speed and average wave speed, which can be useful for observational purposes.