Abstract: Systems and methods configured to control ambient fluid flow for increased energy extraction using a turbine are disclosed. In various examples, a system can include a convergent nozzle configured to receive and accelerate an ambient flow of fluid and a turbine including one or more rotor blades. The convergent nozzle can include a configuration having a ratio of a nozzle inlet area to a nozzle outlet area between about 1.5:1 to about 10:1, inclusive. An interior nozzle surface can include one or more contours aligned with a direction of the ambient flow of fluid. The convergent nozzle can include apertures in a region near a nozzle outlet. The apertures can be selectively controlled to draw additional fluid flow into the accelerated flow to avoid excessive stress on turbine components. The rotor blades can have a length equal to or slightly greater than a radius of the nozzle outlet.