Abstract: A blade includes an elongated body having a leading edge, a trailing edge, a root end, and a tip end, a fluid inlet arranged closer to the root end than the fluid outlet, a fluid outlet arranged near the tip end of the elongated body, and a centrifugal air flow channel defined within the body between the inlet and the outlet to direct air from the inlet to the outlet to issue the flow when the rotor blade is rotating in a rotational path. The blade also includes a valve to selectively open and close the centrifugal air flow channel to selectively issue the flow and change a blade vortex issuing from the rotor blade at discrete portions of the rotational path of the rotor blade. A controller can be operatively connected to the valve to control the valve to open and close the centrifugal air flow channel.