Stokes number

Okay kiddo, so imagine you are playing with a ball and a bucket of water. When you try to throw the ball into the bucket, you might notice that sometimes the ball goes straight into the water, but other times it bounces off the surface of the water. This is because of something called the Stokes law, which talks about how objects move through fluids.

The Stokes law says that if an object is moving through a fluid (like water), then there are tiny particles in the fluid that can slow down the object. These particles are called "fluid drag", and they make it harder for the object to move through the fluid.

Now, let's talk about the Stokes number. The Stokes number is a way to measure how fast an object is moving through a fluid compared to how much the fluid is slowing it down. So, if an object has a small Stokes number, it means that it's moving really fast through the fluid and the fluid drag is not slowing it down very much. But, if an object has a large Stokes number, it means that it's moving slower and the fluid drag is having a bigger effect on it.

So, to sum it up, the Stokes number is a way to measure how much fluid drag is affecting an object as it moves through a fluid. It helps us understand how different objects behave in different fluids, and can be useful in all sorts of scientific and engineering applications.