Methods and devices for producing turbulence in vascular blood flow are provided. In practicing the subject methods, a blood flow modulator is positioned on an external site of a blood vessel at a location in relation to, e.g., at least proximal to a branched vascular site in a manner sufficient to produce turbulence in blood flow at a target site, e.g., at or immediately proximal to the branched vascular site. Representative blood flow modulation devices that find use in the subject methods are devices that can be positioned on an external site of a blood vessel to produce an annular structure around the blood vessel, where the annular structure includes an inner surface protuberance of sufficient dimensions to produce turbulence in the blood vessel. Also provided are kits and systems for practicing the subject methods. The subject methods and devices find use in a variety of applications, including applications to reduce the risk of emboli entering branch blood vessels from a main blood vessel.