A fluidic structure configured to be mounted onto the hub of a fluidic turbine comprising a hub that rotates about a center axis, aligned to a main shaft that contributes torque to the main shaft of the turbine via the principle of lift and/or drag. The fluidic structure can be rigid or have some flexibility. The structure has two or more curved fluidic elements that extend from an upstream tip that aligns to the center axis of rotation, to a downstream end at some further radial position away from the center axis, and rotates about the center axis, wherein the two or more curved fluidic elements contain chord sections that are generally more wide at the upstream position and general more narrow at the downstream position.