A planar fin for use in a heat sink includes turbulent structures extending from the sides of the planar fin. Each turbulent structure defines a longitudinal axis and having a first edge that is parallel to the longitudinal axis and connected to the a planar surface of the fin. Each turbulent structure also includes a second edge opposite the first edged and in free space. The second edge defines a periphery that varies in distance from the first edge along the length of the longitudinal axis. The periphery of each second edge is further shaped such that turbulent flow of a fluid is induced in the flow flowing over the second edge at at least a predefined flow rate.