Cavity Acoustic Tone Suppression

Abstract

Cavity Acoustic Tone Suppression A cavity system for use in a vehicle is provided. The cavity system includes a cavity having at least one of a leading edge and a trailing edge disposed perpendicular to an actual or intended direction of travel of the vehicle, and a longitudinal edge. The leading and / or trailing longitudinal edges define an opening. The cavity system also includes at least one shock stabilizer protruding from a surface adjacent each longitudinal edge of the cavity into an ambient flow outside the cavity. Also provided is an aircraft including the cavity system.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present invention relates to a cavity system for use in a vehicle. Exemplary vehicles include aircraft, and thus exemplary cavities include cavities within bays, such as weapons bays and landing gear bays. [Background technology]

[0002] When a cavity is moving through an ambient fluid, for example an aircraft bay moving through the air, a shear layer forms between the moving ambient air and the still air within the cavity (from the reference point of the aircraft). The shear layer is a thin region of concentrated vortex motion with a large change in tangential velocity component, located across the top of the bay, separating the high-speed and low-speed flows. The vortices shed from the leading edge of the cavity and grow as they move down the shear layer, impinging on the aft (rear) wall of the bay, resulting in noise emission. The sound wave also returns upstream in the bay. As the pressure of the sound wave fluctuates, vortices are either shed from the leading edge cavity lip or the rate of vortex growth increases, resulting in a series of vortices forming down the shear layer at a favorable velocity related to the frequency of the upstream sound wave. The vortices grow into large-scale structures as they propagate downstream of the shear layer and then impinge on the aft (rear) wall of the bay at a characteristic velocity. This results in acoustic noise being generated at a characteristic rate that can be described as an acoustic tone of a characteristic frequency.

[0003] Similar problems exist in other types of vehicles, such as high-performance automobiles with open roofs and windows, and ships at sea with open hatches subject to high impact wind speeds.

[0004] It is known to use spoiler devices in aircraft to redirect the airflow above and beyond the cavity, i.e. above and beyond any boundary layers or possible shear layers, to prevent the above-mentioned effects from occurring. These spoilers are deployed in front of or across the cavity.

[0005] Crossflow (i.e., transverse or lateral flow) also contributes to acoustic noise within the cavity and has been found to be unmitigated using existing spoiler designs.

[0006] Therefore, there is a need for a lightweight mitigation mechanism to reduce or control the effects of acoustic noise within the cavity caused by crossflow. Summary of the Invention

[0007] According to a first aspect, there is provided a cavity system for use in a vehicle, comprising: a cavity having at least one of a leading edge and a trailing edge disposed perpendicular to an actual or intended direction of travel of the vehicle and a longitudinal edge, the leading edge and / or the trailing edge and the longitudinal edge defining an opening; and at least one impact stabilizer protruding from a surface adjacent each longitudinal edge of the cavity into the ambient flow outside the cavity.

[0008] Advantageously, the cavity system, by lifting the shear layer away from the cavity, tends to reduce the effect of cross flows impinging on the cavity as it moves through the fluid or as the fluid moves across the cavity. Thus, the noise in the cavity and thus the resulting damage tends to be reduced. Furthermore, the cavity system allows for better prediction of the payload ejection characteristics beyond the shear layer. The latter is achieved by creating a sufficiently thick shear layer that reduces the flow velocity around any shape or payload in the cavity to prevent it from interacting with the dropped / ejected payload beyond the cavity. Furthermore, the shock stabilizer generates a series of fixed shocks, as opposed to "transient shocks" that move along the direction of cavity movement. Transient shocks make it difficult to predict the loads on the dropped / ejected payload. Thus, it is necessary to flush / eliminate these with fixed shocks that are consistent in location, either increasing the predictability of the loads on the dropped / ejected payload or reducing the range of possible loading solutions.

[0009] The longitudinal edges may be parallel to the actual or intended direction of travel of the vehicle.

[0010] The cavity system may comprise a bay having a front wall, a rear wall, and at least one side wall, the top surface of which comprises a leading edge, a trailing edge, and a longitudinal edge, respectively. There may be one continuous side wall, or two side walls joined by a base. The bay may be a rotating payload bay. Alternatively, the bay may be a fixed payload bay with at least one hinged door across an opening.

[0011] The at least one impact stabilizer may protrude from an upper surface of the at least one sidewall. Alternatively, the at least one impact stabilizer may protrude from an outer skin of the vehicle surrounding the cavity. Alternatively, the cavity system may include first and second spoilers disposed along longitudinal sides of the cavity, with one or more of the plurality of impact stabilizers disposed on an upper surface of each spoiler.

[0012] Each shock stabilizer may include a plurality of peaks. The peaks may be sharp tips.

[0013] At least one impact stabilizer may have an inner surface facing the cavity and first and second outer surfaces facing generally away from the cavity, the first and second outer surfaces being inclined relative to one another about a horizontal axis of the impact stabilizer, and the first and second outer surfaces being coupled to respective edges of the inner surface.

[0014] At least a portion of the inner surface may abut a vertical plane passing through a longitudinal edge of the cavity.The inner surface may be flush with a vertical plane passing through a longitudinal edge of the cavity.

[0015] The first and second outer surfaces may be angled relative to one another about a horizontal and vertical axis of the shock stabilizer. The inner surface may be trapezoidal or triangular.

[0016] The inner surface may be disposed parallel to a longitudinal edge of the cavity. Alternatively, the inner surface may be angled relative to a longitudinal edge of the cavity such that the distance between the inner surface and the cavity increases with distance along the shock stabilizer. The inner surface may be disposed vertically. Alternatively, the inner surface may be disposed at an angle relative to a vertical plane.

[0017] The cavity system may include a third exterior surface disposed between the first exterior surface and the second exterior surface. The third exterior surface may be rectangular, square, or trapezoidal in shape.

[0018] At least one shock stabilizer may include a straight upper edge that is angled toward the base of the shock stabilizer such that the height profile of the shock stabilizer decreases along its length. Instead of a straight upper edge, the shock stabilizer may include a pointed tip. The shock stabilizer may be pyramidal in shape.

[0019] At least one shock stabilizer may include a straight upper edge angled away from a vertical plane passing through an edge of the cavity such that the upper edge has an increasing separation from the longitudinal edge of the cavity along its length. The straight upper edge may be sloped away from the vertical plane and toward the base of the shock stabilizer.

[0020] The upper edge of the at least one shock stabilizer and the longitudinal edge of the cavity may be arranged such that an angle between 5 degrees and 45 degrees is formed therebetween. More preferably, an angle between 10 degrees and 25 degrees is formed between the upper edge of the at least one shock stabilizer and the longitudinal edge of the cavity. Even more preferably, an angle between 15 degrees and 20 degrees is formed between the upper edge of the at least one shock stabilizer and the longitudinal edge of the cavity.

[0021] A top edge of the impact stabilizer may be disposed at an angle relative to bottom edges of the inner surface and the third outer surface such that the third outer surface and the inner surface twist about a vertical axis.

[0022] The at least one impact stabilizer may comprise an inner surface facing the cavity, an outer surface facing generally away from the cavity, a front surface facing the actual or intended direction of travel of the vehicle, and a rear surface facing away from the actual or intended direction of travel of the vehicle, the front surface being concave in contour such that the impact stabilizer forms a slope with respect to an oncoming fluid flow toward the actual or intended direction of travel of the vehicle. The front surface may be oriented to face the actual or intended direction of travel of the vehicle at an angle of 5 to 20 degrees. More preferably, the front surface may be oriented to face the actual or intended direction of travel of the vehicle at an angle of 5 to 10 degrees.

[0023] The cavity system may include lateral spoilers positioned across or in front of the cavity relative to the vehicle's actual or intended direction of travel.

[0024] The cavity system may include a motor for driving the at least one shock stabilizer to be raised from or lowered into a surface adjacent a longitudinal edge of the cavity. The surface may include at least one recess for receiving the at least one shock stabilizer. The recess may have a cover for closing the recess when the at least one shock stabilizer is retracted.

[0025] Alternatively, the cavity system may comprise a motor and the at least one shock stabilizer may comprise a hinge coupled proximate to a longitudinal edge of the cavity, the motor being arranged to drive the at least one shock stabilizer to rotate about the hinge so as to be positioned in the ambient flow in use. A single hinge may be provided for multiple shock stabilizers, i.e. multiple shock stabilizers may be joined to each other by hinges.

[0026] The at least one shock stabilizer may be between 2cm and 20cm in height. The at least one shock stabilizer may be between one boundary layer thickness and six boundary layer thicknesses in height. Preferably, the at least one shock stabilizer is between 3cm and 15cm in height. More preferably, the at least one shock stabilizer is between 4cm and 12cm in height. More preferably, the at least one shock stabilizer is between 5cm and 10cm in height.

[0027] The cavity system may comprise between 3 and 6 shock stabilizers arranged on either side of the cavity. Preferably, the cavity system comprises 4 shock stabilizers arranged on either side of the cavity.

[0028] The shock stabilizers may be arranged in pairs, with one shock stabilizer of each pair of shock stabilizers being arranged on the opposite side of the cavity relative to the other. In other words, the cavity system may include multiple pairs of shock stabilizers, with each pair of shock stabilizers being arranged on opposite sides of the cavity. Both shock stabilizers of a pair may be arranged at an equal distance from the end of the longitudinal edge of the cavity. Alternatively, the shock stabilizers of the pair may be staggered along the length of the cavity, with the first of each pair being at a first distance from the end of the longitudinal edge and the second of each pair being at a second distance from the end of the longitudinal edge. Each pair of shock stabilizers may be spaced apart at an equal distance.

[0029] The cavity system may include a releasable payload, which may be an ordinal such as a bomb or a missile.

[0030] According to a second aspect there is provided an aircraft comprising a cavity system according to any one of the preceding claims. The cavity may be a weapons bay.

[0031] It will be appreciated that features described in relation to one aspect of the invention can be incorporated in other aspects of the invention. For example, an apparatus of the invention can incorporate any of the features described in this disclosure with reference to a method, and vice versa. Moreover, additional embodiments and aspects will become apparent from the following description, drawings, and claims. As can be appreciated from the foregoing and following description, any and all features described herein, and any and all combinations of two or more of such features, and any and all combinations of one or more values ​​defining ranges, are included within the present disclosure, unless the features included in such combinations are mutually inconsistent.

[0032] Embodiments will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 is a perspective view (not to scale) of a rotating payload bay having an impact stabilization system according to an embodiment. [Figure 2a] FIG. 2a is a schematic diagram of the aircraft with rotating payload bay of FIG. 1 in a closed configuration. [Figure 2b] FIG. 2b is a schematic diagram of the aircraft with rotating payload bay of FIG. 1 in an open configuration. [Figure 3a] FIG. 3a is a perspective view of a different design of the shock stabilizer according to an embodiment. [Figure 3b] FIG. 3b is a perspective view of a different design of the shock stabilizer according to an embodiment. [Figure 3c] FIG. 3c is a perspective view of a different design of the shock stabilizer according to an embodiment. [Figure 3d] FIG. 3d is a perspective view of a different design of the shock stabilizer according to an embodiment.

[0034] The same reference numbers are used throughout to denote features of like purpose. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Relative terms such as horizontal and vertical, top and bottom, above and below, front and back, etc., are used above merely for ease of reference in the figures, and it will be understood that these terms are not so limiting, and that any two different orientations or positions, etc., may be implemented rather than truly horizontal and vertical, top and bottom, etc. In particular, for convenience, in FIG. 1, the cavity is shown opening at the top of the page, and therefore, for convenience, the term "top" is used to mean the opening of the cavity, and the term "above" means further away from the cavity. However, it will be understood that the present disclosure also refers to cavities positioned, for example, under the wing or fuselage of an aircraft, i.e., upside down from those shown in FIG. 1, but the use of the term "top" refers to the opening of the cavity, and the use of the term "above" refers to being away from the cavity.

[0036] In general, the embodiments relate to the use of shock stabilizers to reduce the effects of crossflow (i.e., airflow across the cavity perpendicular to the direction of travel of the cavity). These shock stabilizers are located along the longitudinal sides of the cavity (i.e., they are not located across the ends of the cavity), rather than at the front or back of the cavity.

[0037] 1 is a perspective view of a bay 100 (specifically a payload bay) having a pair of shock stabilizers 7a, 7b (generally 7) according to one embodiment. Each of the pair of shock stabilizers 7a, 7b is disposed on an opposite side of the bay 100 relative to the other shock stabilizer 7a, 7b of the pair. Each shock stabilizer 7a, 7b may be directly opposite its partner shock stabilizer 7a, 7b or may be offset from it along the length of the bay 100. There may be an odd number of shock stabilizers 7a, 7b, i.e., there may be no partner on a shock stabilizer 7a, 7b.

[0038] Although a bay 100 is shown for housing a payload 5, such as a missile or camera system, it will be understood that in use the bay 100 may be empty or may be a recess within the structure. The payload 5 may be a deployable payload, or an ordinal, that is released from the bay 100.

[0039] The bay 100 comprises a cavity 2. The cavity 2 is defined by the inner surfaces of the walls of the bay 100. In use, the bay 100 has a fluid (e.g. air) moving through it, and thus the fluid main flow 3 acts in a direction opposite to the actual or intended direction of movement of the bay 100. The bay 100 comprises a leading (i.e. front) wall 8, a trailing (i.e. back) wall 10, and two side walls 12a, 12b (generally 12) defined relative to the actual or intended direction of the main flow 3. In the illustrated embodiment, the cavity 2 comprises a rectangular planar base 1 and has a rectangular opening (i.e. aperture). The side walls 12 and the trailing wall 10 are perpendicular to the flat base 1, while the front wall 8 is inclined relative to the base 1 such that the opening has a perimeter that is greater than the perimeter of the base 1. Each wall 8, 10, 12 has a respective upper surface, one edge of each of which defines a leading edge 14, a trailing edge 16 and side edges 18a, 18b (generally 18) of the cavity 2, i.e. the edges 4, 16, 18 of the cavity 2 define an opening to the cavity 2. The upper surface of each of the walls 8, 10, 12 is coplanar.

[0040] In the illustrated embodiment, the side walls 12 are shown as being longer than the front and rear walls 8, 10, although in other embodiments this may not be the case. For example, the cavity 2 may be relatively wide transversely (i.e. perpendicularly) to the direction of the main flow 3. In these embodiments, references below to "longitudinal edges" should be translated to "transverse edges", i.e. edges parallel to the direction of the main flow 3.

[0041] The bay 100 is a rotational bay having an axis of rotation 4. In the illustrated embodiment, the axis of rotation 4 is aligned with a central longitudinal axis of the bay 100. In other embodiments, the bay 100 may rotate about an axis that is offset to one side of the bay 100, for example along a side edge 18 of the bay 100.

[0042] The bay 100 is driven to rotate about a pivot point 6 through which the rotation axis 4 passes. As shown in Figures 2a and 2b, the bay 100 may be rotationally driven by a motor 9. The bay 100 rotates to expose the payload 5 to an ambient flow (e.g., an ambient air flow).

[0043] In use, there is a cross flow 13 acting on the bay 100. The cross flow 13 is shown as being perpendicular to the actual or intended direction of movement of the bay 100 for the purposes of defining the shapes and angles of the components of the bay 100. That is, the cross flow 13 is shown as being perpendicular to the main flow 3. However, in reality the cross flow will approach the bay 100 over a range of angles.

[0044] In the illustrated embodiment, four shock stabilizers 7 are arranged to protrude from each side of the bay 100 into the surrounding ambient flow in use. The shock stabilizers 7 are arranged on the upper surface of the sidewall 12 (i.e. protruding from, fixed to or integrally formed with the upper surface of the sidewall 12). Alternatively, the shock stabilizers 7 may be arranged on a structure, such as an elongated spoiler, that is itself arranged on the upper surface of the sidewall 12. In other words, the shock stabilizers 7 are arranged on either side of an axis passing through the center of the cavity 2 parallel to the direction of the main flow 3. The shock stabilizers 7 are not arranged forward of the cavity 2, as defined by the leading edge 14.

[0045] In the preferred embodiment shown, the shock stabilizers 7 are positioned such that one side of each is parallel to the side edge 18 of the bay 100. In other embodiments, the shock stabilizers 7 are offset from the side edge 18 of the bay 100. For example, the shock stabilizers 7 may be positioned such that the gap between the point of the shock stabilizer closest to the cavity 2 and the cavity edge 18 is 0.01 to 0.75 times the width of the cavity 2. The gap between the point of the shock stabilizer closest to the cavity 2 and the cavity edge 18 is preferably less than 0.5 times the width of the cavity 2.

[0046] Since the impact stabilizer 7 will interact with high energy flows when installed on the fighter aircraft 200, suitable materials of construction include titanium, steel, or composites such as carbon fiber composites. The impact stabilizer 7 may be made of the same material as the skin of the vehicle in which the bay 100 is installed (or in which the cavity opening is cut). If the bay 100 is installed in an environment with reduced flow velocities and energies, such as a low performance vehicle, a material whose strength or life characteristics are not as well known may be used, such as plastic.

[0047] The design of the further shock stabilizer 7 will be explained later with reference to Figures 3a-3d. In Figure 1, the shock stabilizer 7 takes the form of a pyramid with a triangular base, i.e. a right-angled pyramid. One side (i.e. an edge) of the triangular base is arranged parallel to the edge 18 of the cavity 2. A triangular panel, approximately perpendicular (with respect to the surface to which the shock stabilizer 7 is fixed or otherwise attached), is arranged with its outer surface facing the cavity 2 (i.e. facing the edge 18 of the cavity 2) and is connected to one side of the triangular base. In other words, the triangular panel is shown as being flush with the inner surface of the side wall 12 of the cavity 2. Two further triangular panels (i.e. panels in the form of right-angled triangles) are connected to the two remaining sides of the triangular base. These two further triangular panels are inclined towards the cavity 2 to connect to the first triangular panel on the side facing the cavity 2 and to each other. The shock stabilizer 7 may be open at the bottom, such that the "base" referred to above is the periphery of the opening.

[0048] The two triangular panels generally facing the impinging cross-flow 13 (i.e. away from the cavity 2) are preferably positioned at an angle of between 15 and 70 degrees to the cross-flow 13. In other words, the triangular base preferably has a side parallel to the edge 18 of the cavity and two further edges positioned at between 20 and 75 degrees to that side.

[0049] The height of the shock stabilizer 7 is preferably between 4 cm and 20 cm in height, preferably between 6 cm and 12 cm in height. The width and depth of the shock stabilizer 7 are preferably in the range of 2 cm to 20 cm. The shock stabilizer 7 may have a contour thickness which may be constant, tapered, or irregular.

[0050] The pinnacles (i.e., pointed tips) on the top of the shock stabilizer 7 tend to increase the flow in the cavity 2 through means of inducing vortex flows. The latter tend to help suppress shear layer acoustic effects. Flow mixing is the introduction of new flow components with different direction, circulation, and / or energy to existing flow structures.

[0051] The shock stabilizer 7 utilizes the energetic cross-flow 13 to impart energy to the shear layer, generating an impact at the foot (i.e., base) of the shock stabilizer 7. It is therefore advantageous to increase the surface area of ​​the shock stabilizer 7 facing the impinging cross-flow 13 relative to the surface facing the cavity 2.

[0052] The shock stabilizer 7 in the described embodiment is essentially a vortex generator. Vortex generators are traditionally used to maintain areas of attached flow to support vehicle control surfaces (i.e., whereby the boundary layer has a positive velocity profile from the surface to the free stream). They have not been considered to support mixing in the cavity 2 flow system. The shock stabilizer 7 induces a fixed shock that tends to relocate the shear layer to a higher position above the cavity 2, stabilizing the area of ​​unsteady flow (i.e., the shear layer is moved away from its intrusion into the cavity 2). Unsteady flow is highly nonlinear and turbulent. The fixed shock tends to make the effect of the unsteady flow system over the shear layer more uniform and consistent. In turn, this allows for better prediction of the flow's impact on the payload 5 in the cavity 2 or structures adjacent to the cavity 2.

[0053] Additionally, these shock stabilizer 7 systems tend to reduce the effect of transient shocks on the payload 5 immediately after release from the cavity 2, by either eliminating the transient shocks or limiting their movement. The shock stabilizers 7 introduce shocks at a constant position relative to the plane of the opening of the cavity 2, which has the desired effect of eliminating transient shocks or ensuring that they exert undue force on the payload 5 as it is dropped.

[0054] The shock generated by the shock stabilizer 7 has a fixed position in the volume above the cavity 2. Thus, the released payload 5 interacts with the shock generated by the shock stabilizer 7 at a known position in the flow volume. In the absence of the shock stabilizer 7, expansion (a form of shock where the flow accelerates as opposed to compression where the flow is decelerated) may result from undulations in the shear layer and may transition in the horizontal plane (i.e., across the opening of the cavity 2). Thus, these perturbations / oscillations, or even transient shock positions, make it difficult to predict where the payload 5 will interact with the shock in the ambient flow outside the cavity 2.

[0055] Thus, application of the described shock stabilizer 7 tends to favor the ejection of the payload 5 and reduces detrimental acoustic effects in the cavity flow by inducing mixing.

[0056] A conventional spoiler may be present in the region of the leading edge 14 of the cavity 2 to deflect the fluid flow and thus raise the shear layer. For example, a spoiler may be located forward of the leading edge 14. Conventional spoilers are typically positioned across the cavity 2, i.e. along a transverse axis to the impinging main flow 3. An example of an advantageous spoiler design can be found in GB Patent No. 2514453.

[0057] The four shock stabilizers 7 are shown spaced equidistantly along the length of the cavity 2. However, in other embodiments, the shock stabilizers 7 may be spaced irregularly. At a minimum, the shock stabilizers 7 are spaced apart a distance equal to the maximum height of the shock stabilizers 7.

[0058] Although four shock stabilizers 7 are shown on each side of the cavity 2, in other embodiments, there may be one or more shock stabilizers 7 on each side of the cavity 2. Preferably, there are more than three and no more than six shock stabilizers 7 on each side of the cavity 2. However, in some embodiments, there may be more shock stabilizers 7 on each side of the cavity 2, for example, up to 20 on each side. The shock stabilizers 7 on one side 12 of the cavity 2 are shown as being positioned directly opposite the shock stabilizers 7 on the other side 12 of the cavity 2, i.e., the same distance from the front edge 14 of the cavity. In other embodiments, the shock stabilizers 7 on each side 18 of the cavity 12 are not positioned opposite one another. That is, the shock stabilizers 7 of each pair may be offset from one another along the longitudinal axis of the bay 100.

[0059] The operation of the bay 100 will now be described with reference to Figures 2a and 2b. Here, a fighter aircraft 200 is shown having the bay 100, although it will be understood that the bay 100 may be installed in other forms of vehicles. The bay 100 is shown in cross section, with the remainder of the aircraft 200 shown in schematic form.

[0060] 2a shows the bay 100 in a closed configuration, where the side of the bay 100 having the opening, i.e. the aperture defined by the edges 14, 16, 18 of the cavity 2, faces the inside of the aircraft 200. The exterior surface of the base 1 of the bay 100 faces the ambient atmosphere outside the aircraft 200.

[0061] The bay 100 is shown installed on the ventral side of the fuselage of the aircraft 200. The bay 100 may alternatively be installed on the shoulder of the fuselage or on a wing of the aircraft 200.

[0062] The shaft 11 couples the bay 100 to a motor 9 at the pivot point 6. The motor 9 is, for example, an electric motor. When actuated, the motor 9 drives the shaft 11 to rotate, thereby opening and closing the bay 100. In other embodiments, the motor 9 may be coupled directly to the pivot point 6. In other embodiments, the bay 100 may comprise a motor 9 mechanically coupled to a fixed point on the body of the aircraft 200. In use, the bay 100 may be positioned to extend into the surrounding flow or retract into the interior of the aircraft 200 before rotating to the open configuration. The bay 100 may translate and rotate simultaneously. Alternatively, the bay 100 may be configured to rotate about only one axis 4.

[0063] The outer edge of the base 1, when in the closed configuration, may form a relatively tight seal with the skin of the aircraft 200 surrounding the bay 100. The base 1 may extend beyond the shape defined by the outer surfaces of the walls 8, 10, 12 of the bay 100. In other words, the outer surface of the base 1 is conformal with the skin of the aircraft 200.

[0064] 2b shows the bay 100 in an open configuration, where the motor 9 drives and rotates the bay 100 such that the opening of the cavity 2 faces the ambient atmosphere exposing the payload 5. Thus, the shock stabilizer 7 coupled to the side wall 18 of the bay 100 is shown protruding into the ambient airflow.

[0065] It will be understood that the particular design features will depend on the cavity system and its operating environment, i.e., atmospheric, land or sea. The orientation, height, pinnacle geometry and cross-sectional shape of the shock stabilizer 7 are optimized to support its objectives. Several shock stabilizer 7 designs are described with reference to Figures 3a through 3d. While each of these designs tends to have unique advantages, the concept is not necessarily limited to these designs and other shock stabilizer 7 designs are anticipated to be within the concept of the present invention.

[0066] In these figures, the shock stabilizer 7 is shown having an inner panel 71 facing the cavity 2, an outer panel 72 facing the impinging cross flow 13, a front panel 73 facing generally towards the intended direction of movement of the bay 100 (towards the main flow 3), and a rear panel 74 facing generally away from the intended direction of movement of the bay 100. Rather than the sharp edges of the shock stabilizer 7 shown in Figure 1, the shock stabilizer 7 of Figures 3a-3d is multi-sided. Although the shock stabilizer 7 is shown and described as comprising separate joined panels, these may instead be integrally formed.

[0067] 3a shows an impact stabilizer 7 in the form of a "ski slope". The stabilizer 7 comprises an inner panel 71 having a plane that is orthogonal to the surface to which the impact stabilizer 7 is attached. In other words, in the embodiment shown, the inner panel 71 includes a vertical plane that is parallel to the plane of the cavity sidewall 12. Here, the outer panel 72 is parallel to the inner panel 71 and is laterally offset from the inner panel 71. The inner panel 71 and the outer panel 72 are planar.

[0068] The front panel 73 is connected to the leading edges of the inner panel 71 and the outer panel 72, respectively, and the rear panel 74 is connected to the trailing edges of the inner panel 71 and the outer panel 72. The front panel 73 has a curved surface directed towards the main flow 3. The front panel 73 is concave, so that the panel curves inwards towards the rear of the impact stabilizer 7. In the illustrated embodiment, the front panel 73 is shown orthogonal to the direction of travel of the cavity, i.e. facing towards the impinging main flow 3, but in other embodiments the front panel 73 is oriented towards the main flow 3. In a preferred embodiment, the front panel 73 is positioned such that its surface is oriented between 5 and 20 degrees with respect to the direction of the main flow 3. More preferably, the front panel 73 is positioned such that its surface is oriented between 5 and 10 degrees with respect to the direction of the main flow 3. This increases the surface area of ​​the impact stabilizer 7 that interacts with the cross flow 13.

[0069] The rear panel 74 is flat and disposed perpendicular to the surface to which the shock stabilizer 7 is attached. However, in other embodiments, the rear panel 74 may be curved, similar to the front panel 73, or may be flat and angled relative to the surface to which the shock stabilizer 7 is attached. The rear panel 74 has a rectangular shape.

[0070] FIG. 3b shows a shock stabilizer 7 similar to that shown in FIG. 1, but extending in the direction of the main flow 3. The front panel 73 and the rear panel 74 of the shock stabilizer 7 take the shape of an isosceles triangle. In another embodiment, the front panel 73 and the rear panel 74 of the shock stabilizer 7 take the form of an equilateral triangle. The front panel 73 and the rear panel 74 have the same height and width as each other. The base edges of the front panel 73 and the rear panel 74 are not parallel to each other, but tend to face each other. In another embodiment, the base edges of the front panel 73 and the rear panel 74 are parallel to each other. The front panel 73 and the rear panel 74 are approximately vertical, but are angled inwards to form an acute angle with the edge 18 of the cavity 2. The inside of the front panel 73 and the rear panel 74 are further apart than the outside.

[0071] The outer panel 72 is of rectangular or square profile and is joined to the outside of each of the front panel 73 and rear panel 74. The inner panel 71 has a generally rectangular profile and has a larger surface area than the outer panel 72. The inner panel 73 and outer panel 74 slope towards each other and meet at an apex. The apex is therefore an elongated peak. The base of the impact stabilizer 7 is trapezoidal in shape. In embodiments where the front panel 73 and rear panel 74 are parallel to each other, the base forms a parallelogram (such as a square or rectangle).

[0072] The upper edge of the impact stabilizer 7 (i.e., the side of the impact stabilizer 7 where the inner panel 71 and the outer panel 72 meet) is shown as being parallel to the top surface of the cavity side wall 18, however, because the front panel 73 and the rear panel 74 are the same height, the upper edge of the impact stabilizer 7 may be sloped to decrease in height along its length (i.e., with distance from the front edge 14 of the cavity 2).

[0073] FIG. 3c shows an impact stabilizer 7 similar in design to the impact stabilizer 7 of FIG. 3b, and the common description will not be repeated. Here, the front panel 73 and the rear panel 74 are inclined to the vertical axis and disposed at an acute angle to the edge 18 of the cavity 2. Preferably, the panels 74 are oriented at between about 30 degrees and 60 degrees to both axes, more preferably at about 45 degrees to both axes. Thus, the inner panel 71 and the outer panel 72 connecting the front panel 73 and the rear panel 74 are trapezoidal in shape.

[0074] By angling the front panel 73 and rear panel 74 with respect to the horizontal axis and with respect to the vertical axis, a linear slope is provided which tends to increase the volume of attached flow on the ridges (i.e., apexes), generating small vortices to increase mixing.

[0075] Figure 3d shows the shock stabilizer 7 twisted about its vertical axis (i.e. an axis perpendicular to the surface to which the shock stabilizer 7 is attached). The front panel 73 and rear panel 74 are generally triangular in shape, similar to the shock stabilizer 7 of Figure 3c. The inner panel 71 and outer panel 72 are trapezoidal in the preferred embodiment, but may also be rectangular or square in shape.

[0076] Here, the bottom edges of the front panel 73 and the rear panel 74 are parallel to each other in a horizontal plane (i.e., the plane of the surface to which the shock stabilizer 7 is attached). The front panel 73 and the rear panel 74 are joined to each other by the inner panel 71 and the outer panel 72. Thus, the base of the shock stabilizer 7 defined by the panels 71, 72, 73, 74 is generally rectangular. However, in other embodiments, the front panel 73 and the rear panel 74 can be inclined towards each other in the horizontal plane, making the base trapezoidal.

[0077] The inner panel 71 and the outer panel 72 are inclined inwardly relative to the vertical and meet at an apex (i.e., defining the upper edge of the shock stabilizer 7). The apex is at an angle to the edge 18 of the cavity 2 in the horizontal plane (i.e., has zero vertical inclination). In other words, the upper edge of the shock stabilizer 7 is not parallel to the cavity edge 18. The apex of the shock stabilizer 7 is at an angle of about 20 degrees to the edge 18 of the cavity 2 such that its leading edge is closer to the edge 18 than its trailing edge. This causes the inner panel 71 and the outer panel 72 to be torqued (i.e., to deform in a twisting manner). The axes passing through the apexes of the triangles forming the front panel 73 and the rear panel 74 and perpendicular to the planes of the respective panels 73, 74 are not coaxial. An axis passing through the ends of the lower edges of the front panel 73 and rear panel 74 and the second outer surface (ie, the axis is the bottom edge of the inner panel 71 and the outer panel 72) is disposed obliquely relative to the apex axis.

[0078] In a preferred embodiment, the axis of the apex of the shock stabilizer 7 is at an angle of approximately 20 degrees relative to the edge 18 of the cavity 2 (without tilting or descending), however, the axis of the apex (i.e., the upper edge of the shock stabilizer 7) may be at an angle of approximately 5 degrees to 45 degrees relative to the edge 18, and more preferably at an angle of approximately 10 degrees to 30 degrees relative to the edge 18.

[0079] This design tends to prove particularly advantageous in controlling the flow of fluid impinging on the bay 100. It has been found that the twisted inner panel 71 tends to draw generated vortices towards the outer edges 14, 16, 18 of the cavity 2. In other words, the shear layer tends to be lifted away from the cavity 2.

[0080] In other words, the shock stabilizer 7 has been found to control the flow over the outer edges 14, 16, 18 of the cavity 2 by inducing and retaining a vortex. This vortex acts as a virtual barrier, preventing the external flow from dropping into the cavity 2 and enveloping it in the vortex itself. The elimination of the cross flow, in turn, removes its disturbance to the shear layer, allowing it to grow in height more uniformly across the width of the cavity 2. Thus, the payload 5 and other components within the cavity 2 co-located with the sidewall 12 are better protected. The angle of the ridges (i.e., apexes) is designed to shed vortices that have a directional component away from the cavity 2. This is to prevent the vortex from dropping into the cavity 2.

[0081] Further designs not shown may include shock stabilizer 7 with multiple peaks to increase shear layer mixing. Shock stabilizer 7 may be cylindrical. Alternatively, the shock stabilizer may be a rectangular prism. It will be understood that combinations of these designs of shock stabilizer 7, and those shown in the figures, are within the scope of this disclosure. For example, the shock stabilizer 7 design of FIG. 3c may have a flat top rather than a sharp apex so as to be more cube-like. Additionally, a twist can be introduced along the vertical axis (i.e., the axis perpendicular to the surface to which the shock stabilizer is attached) of the pyramidal design shown in FIG. 1 to bevel the inner panel similar to that of FIG. 3d.

[0082] Although the cavity 2 is shown as having a rectangular base 1 and defined by vertical side walls 12, a vertical rear wall 10, and an inclined front wall 8, it will be understood that the impact stabilizer 7 is applicable to other cavity 2 shapes. For example, all walls 8, 10, 12 may be disposed perpendicular to the horizontal base 1, or some or all of the walls 8, 10, 12 may be disposed at an acute angle to the horizontal base 1. The cavity 2 may include a circular base 1, a triangular base 1, a square base 1, or an irregularly shaped base 1. In other words, for example, if the base 1 is triangular, one of the front wall 8 and the rear wall 10 may be absent, i.e., the longitudinal walls 12 may be inclined inwardly toward each other.

[0083] While the above described embodiment relates to a rotating payload bay 100 having a shock stabilizer 7 suitable for use in an aircraft 200 such as a commercial airliner, a military fighter jet, or a helicopter, in other embodiments the shock stabilizer 7 is suitable for use in other forms of bays 100 and other forms of vehicles. For example, the bay 100 may be a wheel well, the interior of an automobile (i.e. the opening in cavity 2 may be a window or sunroof), an open superstructure, or any other bay 100 through which a fluid moves or through which a fluid moves. The rotating payload bay 100 is applicable to land vehicles such as trains and high performance cars, as well as military vessels such as yachts and submarines.

[0084] The bay 100 may be fixed (i.e. static) rather than rotating and therefore permanently open, or may be provided with a hinged door. The shock stabilizer 7 may be attached to the free end of the hinged door.

[0085] Alternatively, the shock stabilizers 7 may be motorized and arranged to lower into their own cavity when the bay 100 is closed. In other words, the shock stabilizers 7 may lower into the walls 12 of the bay 100, or into the surface surrounding the cavity 2. The shock stabilizers 7 may be driven upwards to extend into the surrounding flow when the bay 100 is open.

[0086] The opening of the cavity 2 may be formed by the skin of the vehicle, i.e. the aircraft 200. In other words, the cavity 2 may not have walls 8, 10, 12, but may be integrally formed with the vehicle.

[0087] Alternatively, the shock stabilizer 7 may be hinged so as to fold into the cavity 2 when the bay 100 is closed (i.e. when its door is closed), or fold out from the cavity 2 into the crossflow 13 when the bay 100 is open.

[0088] The ambient fluid through which the bay 100 moves is described above as an airflow (ie, air stream), but may alternatively be water.

[0089] Although the bay 100 is shown as being rectangular in cross section along its longitudinal axis (i.e., where the base 1 and the two side walls 12 meet at a right angle), it will be understood that the present disclosure encompasses other bay designs, such as those having a semicircular cross section. Such designs effectively have one continuous side wall 12, but have two top surfaces to which the shock stabilizer 7 is attached.

[0090] Although the present invention has been described in relation to some embodiments, it is not intended to be limited to the specific form described herein. Rather, the scope of the present invention is limited only by the accompanying claims. Moreover, although a feature may appear to be described in relation to a particular embodiment, a person skilled in the art will recognize that various features of the described embodiments may be combined in accordance with the present invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

[0091] Adjacent shock stabilizers 7 can have different configurations.

[0092] A singular reference does not exclude a plurality, thus references to "a", "an", "first", "second", etc. do not exclude a plurality. In the claims, the term "comprises" or "includes" does not exclude the presence of other elements.

[0093] Wherever integers or elements having known, obvious, or foreseeable equivalents are referred to in the foregoing description, such equivalents are incorporated herein as if set forth individually. To determine the true scope of the present disclosure, reference should be made to the claims, which should be interpreted to encompass any such equivalents. The reader will also understand that any integers or features of the present disclosure described as optional do not limit the scope of the independent claims. Furthermore, it should be understood that such optional integers or features, while being a possible benefit in some embodiments of the present disclosure, may not be desirable in other embodiments and therefore may not be present.

Claims

1. 1. A cavity system for use on a vehicle, comprising: a cavity having a longitudinal edge and at least one of a leading edge and a trailing edge disposed perpendicular to an actual or intended direction of travel of the vehicle, the leading edge and / or the trailing edge and the longitudinal edge defining an opening; at least one impact stabilizer protruding from a surface adjacent each longitudinal edge of the cavity into an ambient flow outside the cavity.

2. The cavity system of claim 1 comprising a bay having a front wall, a rear wall, and at least one side wall, a top surface of said bay comprising said leading edge, said trailing edge, and said longitudinal edge, respectively.

3. The cavity system of claim 2 , wherein the bay is a rotating payload bay.

4. The cavity system of claim 2 or 3, wherein the at least one shock stabilizer protrudes from an upper surface of the at least one side wall.

5. 4. The cavity system of claim 1, further comprising first and second spoilers disposed along longitudinal sides of the cavity, with one or more of a plurality of impact stabilizers disposed on an upper surface of each spoiler.

6. 6. The cavity system of claim 1, wherein each shock stabilizer comprises a plurality of peaks.

7. the at least one shock stabilizer comprises an inner surface facing toward the cavity and first and second outer surfaces facing generally away from the cavity, the first and second outer surfaces being angled relative to one another about a horizontal axis of the shock stabilizer; 7. The cavity system of claim 1, wherein the first and second outer surfaces are bonded to respective edges of the inner surface.

8. The cavity system of claim 7 , wherein at least a portion of the inner surface abuts a vertical plane passing through a longitudinal edge of the cavity.

9. 9. The cavity system of claim 7 or claim 8, wherein the first and second outer surfaces are angled relative to one another about the horizontal and vertical axes of the shock stabilizer.

10. 10. The cavity system of claim 7, claim 8 or claim 9, wherein the inner surface is disposed parallel to the longitudinal edges of the cavity.

11. 11. The cavity system of claim 7, further comprising a third exterior surface disposed between the first exterior surface and the second exterior surface.

12. 12. The cavity system of claim 11, wherein the at least one shock stabilizer comprises a straight upper edge that is angled toward a base of the shock stabilizer such that a height profile of the shock stabilizer decreases along its length.

13. 13. The cavity system of claim 11 or claim 12, wherein the at least one impact stabilizer comprises a straight upper edge angled away from a vertical plane passing through the longitudinal edge of the cavity, the upper edge increasing in separation from the longitudinal edge of the cavity along its length.

14. The cavity system of claim 13 , wherein the top edge of the at least one impact stabilizer and the longitudinal edge of the cavity are positioned such that an angle between 5 degrees and 45 degrees is formed therebetween.

15. 15. The cavity system of claim 13 or 14, wherein the top edge of the shock stabilizer is disposed at an angle relative to the bottom edges of the inner surface and the third outer surface such that the third outer surface and the inner surface twist about a vertical axis.

16. 7. The cavity system of claim 1, wherein the at least one impact stabilizer has an inner surface facing the cavity, an outer surface facing generally away from the cavity, a front surface facing in the actual or intended direction of travel of the vehicle, and a rear surface facing away from the actual or intended direction of travel of the vehicle, wherein the front surface is concave in profile such that the impact stabilizer forms a slope with respect to an oncoming fluid flow toward the actual or intended direction of travel of the vehicle.

17. 17. A cavity system as claimed in any one of claims 1 to 16, comprising lateral spoilers positioned across or in front of the cavity relative to the actual or intended direction of travel of the vehicle.

18. 18. The cavity system of claim 1 , further comprising a motor for driving the at least one shock stabilizer to raise it out of or lower it into the surface adjacent a longitudinal edge of the cavity.

19. 18. A cavity system as described in any one of claims 1 to 17, comprising a motor, and wherein the at least one shock stabilizer may comprise a hinge coupled proximate to the longitudinal edge of the cavity, wherein the motor is arranged to drive the at least one shock stabilizer to rotate about the hinge so as to be positioned within the ambient flow in use.

20. 20. The cavity system according to any one of claims 1 to 19, wherein the at least one shock stabilizer is between 2 cm and 20 cm in height.

21. 21. The cavity system according to any one of claims 1 to 20, comprising 3 to 6 shock stabilizers arranged on either side of the cavity.

22. 22. The cavity system of claim 1, wherein the shock stabilizers are arranged in pairs, one shock stabilizer of each pair being positioned on an opposite side of the cavity relative to the other shock stabilizer.

23. 23. A cavity system according to any one of claims 1 to 22, comprising a releasable payload.

24. An aircraft comprising a cavity system according to any one of claims 1 to 23.

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