Whirlpools

I can't stop thinking about whirlpools. Which part of it is the fastest - outside or inside? Should be outside, right? At least if we look at other things that rotate, it is supposed to be so. But is whirlpools, does the inside makes the circle equally fast as outside?



If anybody have any ideas, I would appreciate if you shared them. Or else, I will think about whirlpools for a long time. Google didn't help me here.