Fluidic flow over an open cavity may generate impinging shear layers in the fluid. These impinging shear layers may result in pressure oscillations. Free shear layers in an open cavity become unstable and create relatively large vortical structures which may impinge on the trailing edge of the cavity and produce periodic acoustic waves. These waves may propagate upstream in the fluid and impact the shear layer at the layer separation point, thereby causing instability in the fluid.
Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, with emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
The present disclosure relates to implementing noise control of cavity flows using active and/or passive receptive channels. In some embodiments, a channel is formed between a cavity wall and an exterior surface of a body. When a fluid stream flows across the opening of the cavity, the channel facilitates the pressure differential across points near the openings of the channel being lower than would otherwise exist if the channel was not present. In particular, fluid flows through the channel so that the pressure differential is reduced. As a result, the amplitude of pressure oscillations that may be generated from the fluid stream flowing over the cavity is less than what would otherwise be generated if the channel were not present.
With reference to
The body 103 includes a surface 113 that is exposed to the fluid stream 109. Such a surface 113 may be, for example, the exterior skin of an aircraft, the interior wall of a pipe, or any other portion of the body 103 that is exposed to the fluid stream 109. As shown, an opening is formed in the surface 113, which defines a cavity 106 in the body 103. Although the cavity 106 is shown as having a cubical shape, alternative embodiments may comprise cylindrical shapes or any other types of shapes. As non-limiting examples of embodiments of the cavity 106, the cavity 106 may comprise a weapons bay or a landing gear bay in an aircraft. As an additional non-limiting example, the cavity 106 may represent an inlet or an outlet in a pipe.
One or more cavity walls 116-119 define the cavity 106. Additionally, there are edges 123-126 between each respective cavity wall 116-119 and the surface 113. The edge 123 is a leading edge 123 relative to the edge 126, and the edge 126 is a trailing edge 126 relative to the edge 123. In this regard, the leading edge 123 is upstream in the fluid stream 109 relative to the trailing edge 126, and the trailing edge 126 is downstream in the fluid stream 109 relative to the leading edge 123. The embodiment shown in
When the fluid stream 109 flows across the opening of the cavity 106, a relatively high pressure level may exist at the point 133 along the cavity wall 119 near the trailing edge 126, and a relatively low pressure level may exist at the point 136 along the surface 113 near the trailing edge 126. Additionally, a relatively low pressure level may exist at the point 139 along the cavity wall 116 near the leading edge 123, and a relatively high pressure level may exist at the point 143 along the surface 113 near the leading edge 123. Furthermore, unstable sheer layers, which can be described according to the Kelvin-Helmholtz instability theorem, may exist near the surface 113. The pressure differentials at points 133, 136, 139, and 143 in conjunction with the unstable sheer layers may result in pressure oscillations. These pressure oscillations can cause damage to the body 103 and/or objects that are within or near the cavity 106.
With reference to
In the embodiment shown in
A second channel 213 is formed between the cavity wall 116 and the surface 113. The second channel 213 includes one or more channel openings formed in the surface 113 and one or more channel openings formed in the cavity wall 116. As shown, some embodiments of the body 103a include a second edge member 216 that is separate from at least a portion of the surface 113 and at least a portion of the cavity wall 116. In particular, the second edge member 216 is separated from the remaining portion of the surface 113 and the cavity wall 116 by the second channel 213. One or more second support members 223 may provide structural support for the second edge member 216 and maintain the second edge member 216 in position shown.
As discussed above, when the fluid stream 109 flows across the opening of the cavity 106, a relatively high pressure level may exist at the point 133 along the cavity wall 119 near the trailing edge 126, and a relatively low pressure level may exist at the point 136 along the surface 113 near the trailing edge 126. However, because the first channel 203 has one or more channel openings at the point 133 and one or more channel openings at the point 136, the first channel 203 facilitates the pressure differential across the point 133 and the point 136 being lower than would otherwise exist if the first channel 203 were not present. In this regard, the first channel 203 facilitates fluid flowing between the point 133 and the point 136 so that the pressure differential is reduced. As a result, the amplitude of the pressure oscillations that may be generated from the fluid stream 109 flowing over the cavity 106 is less than what would otherwise be generated if the first channel 203 were not present.
Additionally, as discussed above, when the fluid stream 109 flows across the opening of the cavity 106, a relatively high pressure may exist at the point 139 along the cavity wall 116 near the leading edge 123, and a relatively low pressure may exist at the point 143 along the surface 113 near the leading edge 123. However, because the second channel 213 has one or more channel openings at the point 139 and one or more channel openings at the point 143, the second channel 213 causes the pressure differential between the point 139 and the point 143 to be lower than would otherwise exist if the second channel 213 were not present.
With reference to
The body 103b includes one or more plasma actuators 303 and 306. Non-limiting examples of plasma actuators 303 and 306 are described in U.S. Pat. No. 8,235,072, titled “Method and Apparatus for Multibarrier Plasma High Performance Flow Control,” issued on Aug. 7, 2012, U.S. Publication No. 2013/0038199, titled “System, Method, and Apparatus for Microscale Plasma Actuation,” filed on Apr. 21, 2011, and WIPO Publication No. WO/2011/156408, titled “Plasma Inducted Fluid Mixing,” filed on Jul. 6, 2011. Each of these documents is incorporated by reference herein in its entirety. In general, each plasma actuator 303 and 306 is configured to induce the flow of a fluid, such as air or any other type of fluid, due to the electrohydrodynamic (EHD) body force that results from the electric field lines that are generated between respective electrodes of the respective plasma actuators 303 and 306.
The plasma actuators 303 and 306 may be positioned within the first channel 203, as shown in
In some embodiments, the respective plasma actuators 303 and 306 may be dynamically activated in response to the pressure differential that exists across the first channel 203. To this end, one or more sensors (not shown), such as pressure sensors and/or any other suitable type of sensor, may be located near the openings of the first channel 203. The sensors in conjunction with any suitable hardware, software, or combination thereof are used to measure the pressure differential across the first channel 203 and to activate the respective plasma actuators 303 and 306 responsive to the measured pressure differential. For example, if sensors indicate that the pressure level at the point 136 near the surface 113 is greater than the pressure level at the point 133 near the cavity wall 119, the plasma actuator 303 is activated to generate an EHD body force in the direction indicated by the arrow 309. The EHD body force may facilitate fluidic flow in the direction indicated by the arrow 309. As a result, the pressure differential across the first channel 203 may be reduced. Similarly, if sensors indicate that the pressure level at the point 136 near the surface 113 is lower than the pressure level at the point 133 near the cavity wall 119, the plasma actuator 306 may be activated to generate an EHD body force in the direction indicated by the arrow 313. The EHD body force may facilitate fluidic flow in the direction indicated by the arrow 313. As a result, the pressure differential across the first channel 203 may be reduced. Thus, the one or more plasma actuators 303 and 306 may be used to actively attenuate the amplitude of the pressure oscillations that may be generated by the fluid stream 109 (
With reference to
The first channel 203 may take the form of various types of shapes. For example, as shown in
With reference to
With reference to
The controller 1200 in various embodiments may comprise one or more computing devices, such as a microcontroller, a programmable logic device (e.g., a field-programmable gate array (FPGA) or a complex programmable logic device (CPLD)), an application specific integrated circuit (ASIC), a circuit comprising discrete logic elements, or any other suitable device, coupled to the plasma actuators 303 and 306. In some embodiments, the controller 1200 includes at least one processor circuit, having a processor and memory coupled to a bus structure, such as an address/control bus. In addition, the memory may store computing instructions that, when executed by the processor circuit, causes the processor circuit to perform the functionality described herein. Accordingly, the controller 1200 in various embodiments may be embodied in the form of hardware, software, or a combination of hardware and software.
Beginning at element 1203, the controller 1200 measures the pressure levels at points near the openings of the first channel 203. To this end, one or more pressure sensors may be located near the openings of the first channel 203, and the controller 1200 may read values that correspond to the pressure levels. At element 1206, the controller 1200 calculates the pressure differential across the first channel 203.
The controller 1200 then moves to element 1209 and determines whether the pressure differential across the first channel 203 is to be reduced. In one embodiment, the controller 1200 determines to reduce the pressure differential if the pressure differential is greater than a particular value. In another embodiment, the controller 1200 determines to reduce the pressure differential if the pressure differential is increasing from a previously measured pressure differential. If the controller 1200 determines to not reduce the pressure differential, the controller 1200 moves to element 1216.
Otherwise, if the controller 1200 determines to reduce the pressure differential, the controller 1200 moves to element 1213 and activates one or more of the plasma actuators 303 and 306 in order to reduce the pressure differential. For example, if sensors indicate that the pressure level at the point 136 near the surface 113 is greater than the pressure level at the point 133 near the cavity wall 119, the plasma actuator 303 is activated to generate an EHD body force in the direction indicated by the arrow 309. Similarly, if sensors indicate that the pressure level at the point 136 near the surface 113 is lower than the pressure level at the point 133 near the cavity wall 119, the plasma actuator 306 may be activated to generate an EHD body force in the direction indicated by the arrow 313.
As shown at element 1216, the controller 1200 then determines whether the process is complete. If the process is not complete, the controller 1200 returns to element 1203, and the process repeats as shown. Otherwise, the process ends.
Although the flowchart of
Disjunctive language used herein, such as the phrase “at least one of X, Y, or Z,” unless indicated otherwise, is used in general to present that an item, term, etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y, and/or Z). Thus, such disjunctive language does not imply that certain embodiments require at least one of X, at least one of Y, or at least one of Z to each be present.
The above-described embodiments of the present disclosure are merely possible examples of implementations set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiments without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure.
The present application is a non-provisional application of, and claims priority to, U.S. Provisional Application No. 61/977,288, filed on Apr. 9, 2014 and titled “NOISE CONTROL OF CAVITY FLOWS USING ACTIVE AND/OR PASSIVE RECEPTIVE CHANNELS,” which is incorporated by reference herein in its entirety.
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Number | Date | Country | |
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