What is the impact of the free surface effect on ship stability?

The free surface effect refers to the phenomenon that occurs when liquids in a partially filled tank or hold of a vessel are allowed to move freely. This movement can significantly impact a ship's stability. When the liquid shifts due to vessel motion, it causes the center of gravity of the vessel to change, which can lead to a decrease in stability.

As the free surface fluid shifts from one side to another, it effectively causes the ship to roll more than it would otherwise. This movement raises the center of gravity and can shift the metacentric height downward, leading to a lower righting arm. Consequently, the vessel becomes less stable and more susceptible to capsizing in adverse conditions. Therefore, understanding the free surface effect is crucial for maintaining ship stability and ensuring safe operation at sea.