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This research investigates a novel concept in small-scale wind-energy generation. Instead of rotating turbine blades, the present concept produces reciprocating motion that is achieved by alternately activating boundary layer control (slot blowing) on opposite sides of a circular cylinder. This is commonly called the Coandă-effect, and here we deploy it periodically on a spring-stabilized vertical cylinder, to produce reciprocating motion. This Co andă-based Re ciprocating (CoRe) system converts wind energy to mechanical work. Compared to wind turbines and windmills, the CoRe system generates higher torque and is therefore well suited to directly driving positive displacement pumps for drip-irrigation or reverse osmosis water desalination. This new approach necessitates the investment of energy in order to extract energy from the wind and therefore a major challenge is to maximize the output/input ratio in order to render the concept viable. Previous preliminary wind tunnel tests conducted on the CoRe system produced gross and net power coefficients of 10% and 3% respectively. However, the blowing slot design has a decisive impact on output power. On the basis of data presented in the literature and our computational analysis, the CoRe system produces significantly greater torque than all types of wind turbines with net power coefficients over 10%.

Alternating slot-blowing (ASB) on a circular cylinder is used to generate energy from the wind by directly exciting or forcing the vortex shedding instability. Low amplitude excitation produces energetic peaks near the natural vortex shedding frequency, while high amplitude forcing relies on circulation control associated the unsteady Coandă effect to produce energy over a large low-frequency bandwidth. The ASB system produces 3.8 times higher net peak power with a 7.3 times greater bandwidth than a conventional VIV energy harvester, and is potentially a technological game-changer.