An apparatus for driving fluid includes a housing having an interior chamber in communication with a fluid inlet for receiving the fluid and a fluid outlet for expelling the fluid, a cam rotatably mounted within the interior chamber, the cam configured to drive fluid to flow, the cam having an annular channel formed therein, a working vane extending into the annular channel for sliding therein as the cam rotates, wherein the working vane divides the annular channel into an inlet chamber and an outlet chamber such that, as the cam rotates, the inlet chamber expands and the outlet chamber contracts, a follower vane extending into the annular channel for sliding therein as the cam rotates, wherein the follower vane allows fluid to pass in the annular channel, and a rocker arm for providing dependent motion between the working vane and the follower vane.