Abstract: An insert having a plurality of ports creating angled passageways through the walls of the insert is positioned in a drill string for altering fluid flow in the drill string and inducing vibration sufficient to speed up directional drilling and to prevent differential sticking in wellbores. Boundary layer flow along the walls of the drill string is drawn into an upstream group of ports to commingle with fluid in the central bore of the drill string and the insert. The flow is separated at a downstream group of ports and angled passageways cause the flow to be directed radially outward inducing vibration into the drill string.