Now here is a tricky case. This time we have Aphi = k/r, which means that the flow still has an overall swirl. You might guess from the arrows that it has curl, but if you put this Aphi into the curl formula in cylindrical coordinates you will get zero! How can this be if the the field clearly swirls? The answer is found in the confetti test. Notice that the confetti changes shape because of the shear in the flow field, but that it doesn't rotate. (The picture isn't perfect because the confetti is supposed to infinitely small to get exactly zero rotation, but it still gives the right idea.)