Rouse number

Rouse number is like a measurement to see how much a long and skinny object like a piece of spaghetti or a piece of hair will wobble or wiggle when it's moving around in water or some other liquid. It's based on a few things like how thick the liquid is and how heavy the skinny thing is. The higher the Rouse number, the more wiggly or jiggly the skinny thing will be. So if you drop a piece of spaghetti in a bowl of thin soup, it will wiggle a lot more than if you drop it in thick tomato sauce. It's kind of like how a feather will float down slowly through the air, but a rock will fall quickly because it's heavier - but for things that are moving around in water or other liquids instead of air.