Abstract: An actuator configured to rapidly vary the throat geometry of a microjet nozzle. Varying the throat geometry rapidly changes the characteristics of the microjet produced by the microjet nozzle. The inventive device is capable of producing pulsed flow. In some embodiments it is also capable of producing rapidly variable flow in order to provide active control.

Abstract: A system for controlling unwanted flow separation. One or more microjets are placed to feed auxiliary fluid into a region of suspected flow separation on a surface. If the separation is intermittent, sensors can be employed to detect its onset. Once separation is developing, the microjets are activated to inject a stream of high-velocity gas in a direction that is transverse to the prevailing flow. This injected stream forms counter-rotating vortices in the prevailing flow and thereby transfers momentum from the prevailing flow into the boundary layer proximate the surface.

Abstract: A system for controlling unwanted flow separation. One or more microjets are placed to feed auxiliary fluid into a region of suspected flow separation on a surface. If the separation is intermittent, sensors can be employed to detect its onset. Once separation is developing, the microjets are activated to inject a stream of high-velocity gas in a direction that is transverse to the prevailing flow. This injected stream forms counter-rotating vortices in the prevailing flow and thereby transfers momentum from the prevailing flow into the boundary layer proximate the surface.

Abstract: A method of using one or more microjets to create and/or control oblique shock waves. The introduction of microjet flow into a supersonic stream creates an oblique shock wave. This wave can be strengthened—by increasing microjet flow rate or the use of many microjets in an array—in order to form an oblique shock. Such an oblique shock can be used to decelerate flow in a jet aircraft engine inlet in a controlled fashion, thus increasing pressure recovery and engine efficiency while reducing flow instability. Adjusting the pressure ratio across the microjet actually alters the angle of the oblique shock. Thus, the use of microjets allows decelerating shock waves in an inlet engine to be properly positioned and controlled. Microjet arrays can also be used to ameliorate shock waves created by external aircraft surfaces, such as sensor pods and weapons.

Abstract: The present invention comprises a method and associated devices for reducing the noise produced by an open cavity within a moving automobile (such as open sunroofs and open windows). The invention proposes placing microjet orifices proximate the open cavity. These inject small but rapidly moving columns of air into the prevailing flow. The projected columns reduce the formation of large coherent structures in the prevailing flow. As these large coherent structures are a critical component of the resonance which is responsible for much of the noise produced across the open cavity, the overall noise level is reduced by the microjets.

Abstract: A high bandwidth multi-stage microjet actuator. The actuator can produce relatively large amplitude flow disturbances over a broad range of frequencies. The disturbance frequency can be varied by altering the geometry of the device, altering the pressure ratio(s) within the device, and combinations of the two. The actuator has many potential applications, including noise abatement for jet aircraft, and flow control over a moving airfoil.

Abstract: An actuator configured to rapidly vary the throat geometry of a microjet nozzle. Varying the throat geometry rapidly changes the characteristics of the microjet produced by the microjet nozzle. The inventive device is capable of producing pulsed flow. In some embodiments it is also capable of producing rapidly variable flow in order to provide active control.

Abstract: The present invention comprises a method and associated devices for reducing the noise produced by an open cavity within a moving automobile (such as open sunroofs and open windows). The invention proposes placing microjet orifices proximate the open cavity. These inject small but rapidly moving columns of air into the prevailing flow. The projected columns reduce the formation of large coherent structures in the prevailing flow. As these large coherent structures are a critical component of the resonance which is responsible for much of the noise produced across the open cavity, the overall noise level is reduced by the microjets.

Abstract: A high bandwidth multi-stage microjet actuator. The actuator can produce relatively large amplitude flow disturbances over a broad range of frequencies. The disturbance frequency can be varied by altering the geometry of the device, altering the pressure ratio(s) within the device, and combinations of the two. The actuator has many potential applications, including noise abatement for jet aircraft, and flow control over a moving airfoil.

Abstract: A method of using one or more microjets to create and/or control oblique shock waves. The introduction of microjet flow into a supersonic stream creates an oblique shock wave. This wave can be strengthened—by increasing microjet flow rate or the use of many microjets in an array—in order to form an oblique shock. Such an oblique shock can be used to decelerate flow in a jet aircraft engine inlet in a controlled fashion, thus increasing pressure recovery and engine efficiency while reducing flow instability. Adjusting the pressure ratio across the microjet actually alters the angle of the oblique shock. Thus, the use of microjets allows decelerating shock waves in an inlet engine to be properly positioned and controlled. Microjet arrays can also be used to ameliorate shock waves created by external aircraft surfaces, such as sensor pods and weapons.

Abstract: A system for controlling unwanted flow separation. One or more microjets are placed to feed auxiliary fluid into a region of suspected flow separation. If the separation is intermittent, sensors can be employed to detect its onset. Once separation is developing, the microjets are activated to inject a stream of fluid into the separation region. This injected fluid affects the flow and serves to control the flow separation. A steady-state embodiment can be used to continuously fluid. On the other hand, sensors and a rapidly reactive control circuit can be used to inject fluid only when it is needed to inhibit flow separation. The sensors and control circuit can operate off of simple pressure gradient detection or predictive algorithms that anticipate when flow separation will occur.

Abstract: A dynamic cavity air flow system reduces the highly unsteady flow over exposed aircraft cavities by incorporating a series of microjets proximate the leading edge of a cavity. The microjets, which may articulate, issue a supersonic jet flow toward the rear or trailing edge of the cavity whenever the cavity is exposed during flight. The microjets receive the air for the flow from either a dedicated pressurized gas source aboard the aircraft or from bleed air taken from an engine of the aircraft. Appropriate sensors and controllers are provided for control of the system.

Abstract: A microjet based control system helps control the feedback loop that is created by an impinging jet of a STOVL aircraft. A plurality of microjets circumferentially encompass the outer periphery of the impinging jet and each issues a jet flow toward the jet flow created by the impinging jet. A control system is connected to the microjets for adaptively controlling the microjets based on various operating parameters collected by various input devices.