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
Dynamical similarity.
Essentially you have to scale other factors as well as the ship (e.g. the surface of the model needs to be smoother, speed changes between model and real life etc.).
There’s a method in fluid dynamics called dimensional analysis – which is the method of finding “non-dimensional” parameters (variables which have no units of mass, length, time etc.) which must be constant between the model and the real ship, and you can use this to find out numerically exactly how much you need to scale everything else by in order to get an accurate test.
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