A Kármán vortex street is a repeating pattern of swirling vortices caused by the unsteady separation of flow over bluff bodies. They are named after the engineer and fluid dynamicist, Theodore von Kármán.
When a vortex is shed, an asymmetrical flow pattern forms around the body, which therefore changes the pressure distribution. This means that the alternate shedding of vortices can create periodic lateral forces on the body in question, causing it to vibrate. If the vortex shedding frequency is similar to the natural frequency of a body or structure, it causes resonance. It is this forced vibration which, when at the correct frequency, causes suspended telephone or power lines to “sing”, the antennae on your car to vibrate more strongly at certain speeds and it is also responsible for the fluttering of Venetian blinds as the wind passes through them, and causes these vortices.