Eli5: How do they effectively test scale models of giant ships in water? Doesn’t the water behave differently in the small vs large scale?

Question

Eli5: How do they effectively test scale models of giant ships in water? Doesn’t the water behave differently in the small vs large scale?

In: Physics

Answer 1

There’s something called the Froude number, which is a number that represents the relationship between how heavy a bit of water is, its weight, and how that same bit of water will resist any sort of movement, its inertia. The Froude number needs to remain the same for any scale, and that number helps people find the right scaling factors for different components of the model, such as how fast the model should go, how big the waves should be, how large the scale should be, etc. Time would also need to be slowed down by the same factor, and that would be done by slowing down video recordings of the test. Check out the Veritasium video that talks about your exact question.