Question: how can you test that the subs swim how they suppose to ( please give a long answer)?

Ryan Ladd answered on 22 Jun 2011:

In my laboratory we have a test swimming pool where we experiment on the submarines. It’s not just a normal swimming pool though, it’s what’s called a swimmers treadmill – it has some big pumps which create a flow in the pool meaning you could swim as long as you like but never go anywhere! This is ideal for testing our small submarines.

To make sure they’re swimming as they’re supposed to, we use lots of different methods. The simplest is just watching them, often you can see if there’s something wrong with just your eyes!

Otherwise we can video them with underwater cameras and then view the films in slow motion, we even have come computer software which can automatically track the movement of the fins or submarine to analyse the motion.

Alternatively, we often use position sensors or strain gauges which measure where the fins are and the forces they experience directly.

Finally, we can use a method called PIV – Particle Image Velocimetry. This uses a laser sheet to illuminate tiny particles in the water around the submarine fins, we then use a very high speed camera (which can take hundreds of photos a second!) to show where the particles move. A computer then analyses the motion of the particles and can be used to show some really amazing results about how the fins are moving and what the water is doing!

I hope that was long enough for you!