The separation of flow over a body such as an aircraft wing can cause substantial loss of lift and reduction in the overall fuel efficiency of the aircraft. Delaying or elimination of the separation of flow can help in decreasing fuel consumption and decreasing emissions, thus producing a more fuel efficient–greener aircraft.
Fluidic oscillators can be used as active flow control devices which produce oscillating output flow, which can be used for effective flow control. These oscillators use the phenomenon of Coanda effect (the tendency of a jet of fluid to be attached to the adjacent wall). A series of fluidic oscillators in an array can produce oscillating flow for an entire span of an aircraft wing. Fluidic devices have no moving parts and hence, can be used for long periods with low maintenance requirements.
The present invention encompasses an automated system which can automatically control flow on the surface of an aerofoil section, such as an aircraft wing, at varied free stream flow velocities and at varied angles of attack. The invention is the derived work of the entrant's graduate research work and based on the up-to-date research work performed by other researchers around the globe.
The required value of input pressure for a given free stream velocity, for a given angle of attack, for a given design of aerofoil section and for given fluidic oscillator dimensions, which is to be supplied to the fluidic oscillator to obtain the desired flow separation control are preset in the on-board computer. Flow separation control can be effectively performed only if the exit flow velocities and flow frequencies from the surface hole of the aerofoil section matches free stream velocity and the angle of attack of the aerofoil section. An onboard computer gets data from gyro, air speed indicator and calculates the necessary input pressure required for the fluidic oscillator system based on preset laboratory test values. The corresponding pressure of air from the engine bleed valve is released into the array of fluidic oscillators. The fluidic oscillator then produces the necessary switching frequency and exit flow velocities so as to produce the required flow control. The preset values on the on-board computer varies with the type of aerofoil section used, the dimensions of the aerofoil section and the dimensions of the fluidic oscillator system used.
Potential customers include manufacturers of unmanned and passenger aircraft. In addition, the system can be modified to be used in wind turbines both for increasing its efficiency and for induced stalling of the turbine blades, when it exceeds the rated power.
Fabricating the fluidic oscillator system is made possible with the help of micron-precision machining and the other components that make up the system are available off-the-shelf or can be manufactured at very low costs compared to any system available in the market.
The system proves to be a simple yet cost-effective technology, with low maintenance requirements and which can be optimized for a particular aircraft.
Note:Sample aerofoil-encasing shown in the diagram is only for demonstration purposes.