Aerodynamic structures exhibiting reduced drag at supersonic speeds

Abstract

A nose cone 100 for reducing drag at supersonic speeds, comprises a frontal right conical body 112 and a rear cylindrical body 114. The nose cone has a pointed front end 116 and a blunt rear end 118. The conical body 112 includes a plurality of air intake apertures 122; and a network of air inlet passages 134 leading into the air inlet passages, terminating in convergent nozzle sections. The cylindrical body 114 defines frontal and rear aerodynamic surfaces 120, 120.1, respectively, over which airflows. The cone 100 includes a plurality of air venting apertures 124; and a network of air outlet passages 126 in flow communication with the air venting apertures 124 and the air inlet passages 134. The air outlet passages 126 define divergent nozzle sections adjacent the air inlet passages. A throat 128 is defined between each air inlet passage 134 and an associated air outlet passage 126, at which airflow is momentarily choked. The air inlet and outlet passages and the throat together comprise a convergent-divergent nozzle.

Description

[0001] AERODYNAMIC STRUCTURES EXHIBITING REDUCED DRAG AT SUPERSONIC SPEEDS

[0002] TECHNICAL FIELD

[0003] This invention relates to an aerodynamic structure which is exposed to airflow at supersonic speeds. It relates particularly to an aerodynamic structure which exhibits reduced drag when exposed to airflow at supersonic speeds.

[0004] Any reference in this specification to “supersonic speed” shall be interpreted to mean a speed greater than Mach 1 .

[0005] Any reference in this specification to “hypersonic speed” shall be interpreted to mean a supersonic speed between Mach 5 and 10.

[0006] Any reference in this specification to a body of revolution (BOR) shall mean a solid body obtained by rotating a plane figure about an axis within the plane of the plane figure.

[0007] Any reference in this specification to a “nose cone” shall be interpreted to mean a conically-shaped forwardmost part of a vehicle, rocket, guided missile or the like, designed to modulate oncoming airflow behaviours and minimize aerodynamic drag. BACKGROUND TO INVENTION

[0008] The reduction of drag in aerodynamic vehicles has for many years focussed mainly on aerodynamic shape optimisation. With each new generation / version of a vehicle, particular performance criteria of different parts (e.g., wing, nose, fuselage etc.) are improved using shape optimisation algorithms and / or software. The existing geometry is run through a computer program, which identities certain weaknesses in the design. The software is used to resolve problems and rectify weaknesses in the design, outputting an improved, better solution with a marginal performance improvement.

[0009] Aerodynamic shape optimisation is typically performed using software code / analytic software such as computational fluid dynamics (CFD) and Finite Element Analysis (FEA) algorithms. CFD requires a method to parameterise the surface, a method to deform the surface and a volume mesh related to the chosen shape control parameters (such as geometric constraints for payload size etc.), a method to obtain the sensitivity of an objective function to each parameter, and a method to use these sensitivities to improve the design.

[0010] It is also known to use a combination of several types of optimization theory combined with computational modelling and programming (CFD / FEA) in an iterative style to meet certain criteria. This method lacks meaningful performance improvements due to many years of repeated use and optimisation.

[0011] There are a number of problems with the abovementioned approaches to drag reduction. The methods are computationally expensive and time consuming. Only the outer surface geometry can be changed resulting in limited improvement due to limited space. There is only so much that can be done with an outer surface and so much that can be improved, and this has essentially already been achieved. The same outer surface shapes are repeatedly used and / or refined. The methods have also already been optimized and perfected. From the 1960s, the same software codes and processes have been refined and repeated over many years. Computation speed, sophistication, and optimisation methods have improved, however, since the inputs of each cycle are usually the previous-generation optimised part, a performance improvement ceiling has been reached. A previously-optimised shape is run through a perfected optimisation software, over many iterations. The result is an ‘improved’ product with little performance improvements. The most efficient solid shapes have already been created using this solution, proved by few visible geometric changes or data improvement for a long time. This has been the common method for aerodynamic optimisation since modern supercomputing became viable.

[0012] Alternative prior art methods of reducing drag by flow redistribution methods, including adding components, for example, adding an aerospike to the nose, or removing material, for example, introducing a porous system.

[0013] In recent years, meaningful research has been done on the removal of material. (Poplavskaya, T. V., Kirilovskiy, S. V., Mironov, S. G., & Tsyryulnikov, I. S. (2019). Numerical simulation of highly porous materials in application to supersonic aerodynamics . AIP Conference Proceedings). The research team investigated a high- porosity cellular material (HPCM) model in supersonic flow. Solid cylindrical models of various diameters, having frontal inserts made of cellular-porous nickel with the mean pore diameters d = 1 , 2, 3, and 4 mm and a porosity of k=0.95 (95% porous) were tested with cylinders having frontal high porosity inserts and cylinder made entirely of HPCM. The aerodynamic drag was found to be significantly reduced using the porous inserts. They found that cellular materials (porous and aerofoam-like materials) could effectively be used in supersonic aerodynamics.

[0014] The problem with such high porous material is that in real-life, a nose cone or other aerodynamic structure, has a required function of holding a payload, among other things, and cannot be so highly porous. It also cannot be a cylindrical shape. HPCM (and similar porous materials such as aerofoam) cannot be moulded or manufactured into ogives and other complex shapes, meaning this type of porous design is simply not feasible, even though the drag reduction was found to be good. It is an object of the present invention to use modern scientific principles and manufacturing techniques to provide an aerodynamic structure which addresses the shortcomings of the abovementioned prior art methods for reducing drag in aerodynamic structures.

[0015] SUMMARY OF INVENTION

[0016] According to the invention there is provided an aerodynamic structure which is exposed to airflow at supersonic speeds, the aerodynamic structure including:

[0017] A) an aerodynamic outer surface over which air flows;

[0018] B) an air intake arrangement comprising: b1) a plurality of air intake apertures defined in the aerodynamic outer surface at a forward section thereof; b2) a network of air inlet passages wherein each air inlet passage extends inwardly from a particular one of the intake apertures and terminates in a convergent nozzle section;

[0019] C) an air venting arrangement comprising: c1) a plurality of air venting apertures defined in the aerodynamic surface at a rearward section thereof; and c2) a network of air outlet passages wherein each air outlet passage is in flow communication with the air inlet passages and has a divergent nozzle section adjacent the air inlet passage and terminates at a particular one of the air venting apertures for venting air therefrom; and

[0020] D) a throat formation defined between each air inlet passage and an associated air outlet passage, at which airflow between the air inlet and outlet passages is momentarily choked. In use, the aerodynamic structure is designed for reducing drag when exposed to an airflow at supersonic speeds.

[0021] The aerodynamic structure may be in the form of a two-dimensional or three- dimensional body of revolution (BOR). It will be appreciated that the BOR may comprise any structures which are exposed to supersonic airflows, whether airborne or grounded. Examples of such structures may comprise structures forming part of projectiles such as rockets, missiles, spacecraft, hypervelocity projectiles, supersonic aircraft, supersonic automobiles and parts thereof, ammunition such as bullets, aircraft engine intakes and the like.

[0022] A specific example of a three-dimensional BOR envisaged in accordance with the invention, is a nose cone of a vehicle exposed to supersonic airflows, such as an aircraft. It will, however, be appreciated that the aerodynamic structure may have a variety of different shapes and configurations depending on its application.

[0023] The shape of a nose cone of a rocket designed for re-entry into earth’s atmosphere, for example, will generally have a blunter profile such as a hemispherical or ellipsoidal profile. For vehicles operating within earth’s atmosphere where density effects are present, sharper nose profiles such as ogives and right cones are generally preferred.

[0024] The convergent nozzle section of each air intake passage, the divergent nozzle section of the air outlet passage associated therewith and the throat formation defined between the convergent and divergent nozzle sections, together comprise a convergent- divergent nozzle formation. The configuration of the convergent-divergent nozzle formation is such that subsonic airflow enters the air inlet passage where the converging geometry of the convergent nozzle section accelerates the airflow to choke at the throat formation where the mass flow reaches its maximum level. The airflow is accelerated by the diverging geometry of the divergent nozzle section to supersonic speeds where the airflow reaches its maximum speed at an outlet end of the divergent nozzle section. It will be appreciated that the fluid momentum transfer and thus drag reduction, is achieved in the convergent-divergent nozzle formations using changes in ratios of cross-sectional areas of the convergent and divergent nozzle sections and of the throat formations, pressure and velocity gradient changes and mass flow conservation within the convergent-divergent nozzle formations.

[0025] For an aerodynamic structure in the form of a solid body including a conical structure having front end at a narrow end of the conical structure and rear end at a wider end of the conical structure, the air inlet passages may be arranged in different configurations for different applications.

[0026] In one embodiment, the aerodynamic structure may include air inlet passage sections having a toroidal configuration. The air inlet passage sections may be arranged in a series of spaced toroidal passage sections wherein centres of the passage sections coincide with a longitudinal cone axis extending through a centre of the conical structure. More specifically, the toroidal passage sections may conform to the geometry of the conical structure, with a forwardmost toroidal passage section having the smallest overall cross-sectional diameter and a rearmost toroidal passage section having the largest overall cross-sectional diameter. The cross-sectional diameters of the toroidal passage sections may increase incrementally from the front end towards the rear end of the conical structure. The toroidal passage sections may be arranged in an equi-spaced arrangement within the conical structure.

[0027] In a specific arrangement, the forwardmost toroidal passage section may be located at a location about 25% from a tip of the conical structure, calculated along a length of the cone axis. The rearmost toroidal passage section may be located at a location about 90% from the tip of the conical structure, calculated along the length of the cone axis. The spacing between the toroidal passage sections may be approximately 1mm.

[0028] The aerodynamic structure may additionally include air inlet passage sections having a longitudinal configuration. The longitudinal passage sections may intersect and be in flow communication with the toroidal passage sections in an arrangement wherein the longitudinal passage sections extend from the forwardmost toroid passage section to the rearmost toroid passage section. More specifically, each longitudinal passage section passes through each toroidal passage section thereby linking the toroidal passage section to the longitudinal passage section. The longitudinal passage sections may be arranged in a spaced arrangement around the cone axis. The longitudinal passage sections have rectilinear configurations. More particularly, the longitudinal passage sections may be inclined at an angle relative to the cone axis wherein the longitudinal passage sections are tapered towards the tip of the conical structure. The angle of inclination of the longitudinal passage sections may be approximately 8 degrees.

[0029] The aerodynamic structure may yet additionally include air inlet passage sections having a radial configuration. The radial passage sections may intersect and be in flow communication with the toroidal passage sections in an arrangement wherein the radial passage sections extend inwardly from the air intake apertures to the toroidal passage sections. More specifically, each radial passage section extends inwardly from a particular one of the air intake apertures to a closest one of the toroidal passage sections, thereby linking the toroidal passage sections with the air intake apertures, thereby providing for re-distribution and dispersion of airflow entering the conical structure through the air intake apertures.

[0030] The air intake apertures may be arranged on the aerodynamic outer surface of the conical structure with a spacing between outer edges of the air intake apertures, of between 1 - 1.5mm. The air intake apertures may comprise approximately 30% of the total outer surface of the conical structure.

[0031] The air inlet passages may have circular cylindrical profiles. The Applicant envisages, however, that in other embodiments of the invention, the air inlet passages may have non-circular profiles. In use, the radial passage sections provide for an inflow of air into the conical structure. The toroidal passage sections allow for air to circulate within the conical structure while at the same time allowing for airflow within the longitudinal and toroidal passage sections to mix. The longitudinal passage sections provide the main source of flow towards the air outlet passages.

[0032] The air venting apertures may be located at a rear section of the solid body, with the air outlet passages extending rearwardly between the toroidal passage sections and the air venting apertures. More specifically, each air outlet passage may extend between a particular one of the air venting apertures and the rearmost toroidal passage section. The air outlet passages may be arranged in an equi-spaced arrangement around the cone axis. The solid body may include a rear body structure at a rear end of the conical structure in which the air venting apertures are defined. More specifically, the rear body structure may have a cylindrical configuration. The air venting apertures may be defined in the rear body structure with the air outlet passages being arranged in a circumferential equi-spaced arrangement at an orientation of 45 degrees with respect to the cone axis.

[0033] The throat formations may be defined at the junctures between the toroidal passage sections, the longitudinal passage sections and the radial passage sections and the air outlet passages associated therewith.

[0034] BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Further features of the invention are described hereinafter by way of non-limiting examples of the invention, with reference to and as illustrated in the accompanying diagrammatic drawings. In the drawings:

[0036] Figure 1 shows a three-dimensional view of an aerodynamic structure in accordance with the invention, in the form of a right nose cone for a vehicle designed for travel at supersonic speeds; Figure 2 shows a front end view of the right nose cone of Figure 1 showing internal details of passages within the right cone in broken lines;

[0037] Figure 3 shows a side view of the right nose cone of Figure 1 showing internal details of passages within the right cone in broken lines;

[0038] Figure 4 shows a sectional side view of the right nose cone of Figure 1 , sectioned along section line IV - IV of Figure 2;

[0039] Figures 5A and 5B show sectional side and external side diagrammatic representations, respectively, of toroidal internal air inlet passages of the right nose cone of Figure 1 ;

[0040] Figures 6A - C show sectional side, external side and sectional three-dimensional diagrammatic representations, respectively, of longitudinal internal air inlet passages of the right nose cone of Figure 1 ;

[0041] Figures 7A - 7C show sectional side, external side and sectional three-dimensional diagrammatic representations, respectively, of radial air inlet passages of the right nose cone of Figure 1;

[0042] Figure 8 shows a graphical representation illustrating the principle of a convergingdiverging nozzle formed by the combination of the convergent nozzle section of each air intake passage, the divergent nozzle section of the air outlet passage associated therewith and the throat passage section defined between the convergent and divergent nozzle sections;

[0043] Figure 9 shows a schematic fragmentary longitudinal section through the right nose cone of Figure 1 ;

[0044] Figure 10 shows a first schematic fragmentary cut-away three-dimensional view of the right nose cone of Figure 1 , sectioned along section line X - X of Figure 4, illustrating the inter-connection of the radial air intake passages, the innermost toroidal air inlet passages and the air outlet passages;

[0045] Figure 11 shows an end view of the sectional view shown in Figure 10;

[0046] Figure 12 shows a schematic fragmentary sectional three-dimensional view of the section shown in Figure 9;

[0047] Figure 13 shows a three-dimensional view of another embodiment of a right nose cone for a vehicle designed for travel at supersonic speeds, in accordance with the invention;

[0048] Figure 14 shows a front end view of the right nose cone of Figure 13;

[0049] Figure 15 shows a sectional view of the right nose cone of Figure 13, sectioned along section line XV -XV of Figure 14;

[0050] Figure 16 shows a sectional view of the right nose cone of Figure 13, sectioned along section lines XVI -XVI of Figure 14;

[0051] Figure 17 shows a side view of the sectional view shown in Figure 16;

[0052] Figure 18 shows another planar section through a three-dimensional view of the right nose cone of Figure 13;

[0053] Figure 19 shows a sectional side view of the sectioned three-dimensional view of Figure 18;

[0054] Figure 20 shows a side view of the right nose cone of Figure 13, showing internal details of passages within the nose cone in broken lines; Figures 21 A - 21 D show three-dimensional, sectioned three-dimensional, sectioned side and front end views, respectively, of an aerodynamic structure in accordance with the invention, in the form of a hemispherical nose cone;

[0055] Figures 22A - 22D show three-dimensional, sectioned three-dimensional, sectioned side and front end views, respectively, of an aerodynamic structure in accordance with the invention, in the form of a secant ogive nose cone; and

[0056] Figures 23A - 23D show three-dimensional, sectioned three-dimensional, sectioned side and front end views, respectively, of an aerodynamic structure in accordance with the invention, in the form of an ellipsoid nose cone.

[0057] DETAILED DESCRIPTION OF THE DRAWINGS

[0058] With reference initially to Figures 1 - 12 of the drawings, an aerodynamic structure for reducing drag when exposed to airflow at supersonic speeds in accordance with the invention, in the form of a right nose cone, is designated by the reference numeral 10.

[0059] The nose cone 10 has a unitary structure comprising a frontal right conical body 12 and an integrally-formed rear cylindrical body 14 disposed rearwardly of the conical body 12. The nose cone has a pointed front end 16 defined by the conical body and a blunt rear end 18 defined by the cylindrical body 14.

[0060] The conical body 12 defines a frontal aerodynamic outer surface 20 over which air flows. The conical body 12 includes an air intake arrangement comprising a plurality of air intake apertures 22 in the frontal aerodynamic outer surface 20; and a network of air inlet passages wherein each air inlet passage extends inwardly from a particular one of the intake apertures and terminates in a convergent nozzle section.

[0061] The cylindrical body 14 defines a rear aerodynamic surface 20.1 over which air flows. The cylindrical body 14 includes an air venting arrangement comprising a plurality of air venting apertures 24 defined in the aerodynamic surface 20.1 ; and a network of air outlet passages 26 wherein each air outlet passage is in flow communication with the air inlet passages and has a divergent nozzle section adjacent the air inlet passages and terminates at a particular one of the air venting apertures 24 for venting air therefrom.

[0062] A throat formation 28 is defined between each air inlet passage and an associated air outlet passage 26, at which airflow between the air inlet and outlet passages is momentarily choked.

[0063] The convergent nozzle section of each air inlet passage, the divergent nozzle section of the air outlet passage 26 associated therewith and the throat formation 28 defined between the convergent and divergent nozzle sections, together comprise a convergent-divergent nozzle formation. The configuration of the convergent-divergent nozzle formation is such that subsonic airflow enters the air inlet passage where the converging geometry of the convergent nozzle section accelerates the airflow to choke at the throat formation 28 where the mass flow reaches its maximum level. The airflow is accelerated by the diverging geometry of the divergent nozzle section to supersonic speeds where the airflow reaches its maximum speed at an outlet end of the divergent nozzle section.

[0064] Figure 8 provides a graphical representation illustrating the principle of the convergingdiverging nozzle formed by the combination of the convergent nozzle section of each air inlet passage, the divergent nozzle section of the air outlet passage 26 associated therewith and the throat formation 28 defined between the convergent and divergent nozzle sections. Basic flow principles of a convergent - divergent nozzle are used to draw in airflow from the atmosphere through the air intake apertures 22, choke the airflow inside the air inlet passages and at the throat formations 28 and then accelerate the airflow to supersonic exit speeds through the air outlet passages 26. In Figure 8:

[0065] A1 = the sum of all the face areas of the air intake apertures 22 in the aerodynamic surface 20 of the conical body 12. A* = the sum of all the face areas at the throat formations 28.

[0066] A2 = the sum of all the face areas of the air venting apertures 24 in the aerodynamic surface 20.1 of the cylindrical body 14, parallel to the airflow direction.

[0067] It will be appreciated that the fluid momentum transfer and thus drag reduction, is achieved in the convergent-divergent nozzle formations using changes in ratios of cross-sectional areas of the convergent and divergent nozzle sections and of the throat formation, pressure and velocity gradient changes and mass flow conservation within the convergent-divergent nozzle formations.

[0068] The air inlet passages comprise a network of inter-connected toroidal air inlet passages 30, longitudinal air inlet passage 32 and radial air inlet passages 34 having toroidal, longitudinal and radial configurations, respectively.

[0069] Figures 5A and 5B show sectional side and external side diagrammatic representations, respectively, of the toroidal passages 30. The toroidal passages 30 are arranged in an- equi-spaced configuration wherein centres of the toroidal passages coincide with a longitudinal cone axis C extending through a centre of the conical body 12. The toroidal passages 30 conform to the geometry of the conical body, with a forwardmost toroidal passage 30.1 having the smallest overall cross-sectional diameter and a rearmost toroidal passage 30.2 having the largest overall cross-sectional diameter. The cross- sectional diameters of the toroidal passages increase incrementally from the front end towards the rear end of the conical body.

[0070] The forwardmost toroidal passage 30.1 is located at a location about 25% from a tip of the conical body 12, calculated along a length of the cone axis C. The rearmost toroidal passage 30.2 is located at a location about 90% from the tip of the conical body, calculated along the length of the cone axis. The spacing between the toroidal passages 30 is approximately 1mm. It will be appreciated that the specific dimensions and configuration of the toroidal passages may vary greatly, depending on the geometry and dimensions of the cone body and the drag reduction to be achieved.

[0071] Figures 6A - C show sectional side, external side and sectional three-dimensional diagrammatic representations, respectively, of the longitudinal passages 32. The longitudinal passages 32 are in flow communication with the toroidal passages 30 and intersect the toroidal passages in an arrangement wherein the longitudinal passages extend from the forwardmost toroid passage 30.1 to the rearmost toroidal passage 30.2. More specifically, each longitudinal passage 32 passes through each toroidal passage 30 thereby linking the toroidal passages to the longitudinal passages. The longitudinal passages are arranged in a spaced arrangement around the cone axis C and have rectilinear configurations. The longitudinal passages inclined at an angle relative to the cone axis C wherein the longitudinal passages taper towards the front end 16 of the conical body 12. The angle of inclination of the longitudinal passage sections is approximately 8 degrees. It will be appreciated that the specific dimensions and configuration of the longitudinal passages may vary greatly, depending on the geometry and dimensions of the cone body and the drag reduction to be achieved.

[0072] Figures 7A - 7C show sectional side, external side and sectional three-dimensional diagrammatic representations, respectively, of the radial internal passages 34. The radial passage sections may intersect and be in flow communication with the toroidal passage sections in an arrangement wherein the radial passage sections extend inwardly from the air intake apertures to the toroidal passage sections. Each radial passage 34 extends inwardly from a particular one of the air intake apertures 22 to a closest one of the toroidal passages 30, thereby linking the toroidal passages 30 with the air intake apertures 22, thereby providing for re-distribution and dispersion of airflow entering the conical body 12 through the air intake apertures. The toroidal passages 30 allow for air to circulate within the conical structure while at the same time allowing for airflow within the longitudinal and toroidal passages to mix. The longitudinal passages 32 provide the main source of flow towards the air outlet passages 26.

[0073] The air outlet passages 26 extend rearwardly between the toroidal passages 30 and the air venting apertures 24. Each air outlet passage extends between a particular one of the air venting apertures 24 and the rearmost toroidal passage 30.2. The air outlet passages 26 are arranged in an equi-spaced arrangement within the cylindrical body 14 around the cone axis C in a circumferential equi-spaced arrangement at an orientation of 45 degrees with respect to the cone axis.

[0074] The throat formations 28 are defined at junctures between the toroidal passages 30, the longitudinal passages 32 and the radial passages 34 and the air outlet passages 26 associated therewith.

[0075] Figures 9 - 12 show various sectional views of the nose cone 10 further illustrating the air inlet passages and the air outlet passages.

[0076] Figures 13 - 20 show various views of another embodiment of an aerodynamic structure in accordance with the invention in the form of a right cone designated by the reference numeral 100. The right cone 100 is similar to the right cone 10 with the only difference being that the right cone has a different geometry and configuration to that of the right cone 10. The right cone 100 includes all of the broad features of the right cone 10 providing the right nose cone 100 with drag resistance properties under supersonic flow conditions. As such, features of the right cone 100 that are similar to those of the right cone 10 are designated by similar reference numerals in the drawings.

[0077] Figures 21 A - 21 D show three-dimensional, sectioned three-dimensional, sectioned side and front end views, respectively, of an aerodynamic structure in accordance with the invention, in the form of a hemispherical nose cone designated generally by the reference numeral 200. The hemispherical nose cone 200 is similar to the right cone 10 with the only difference being that the hemispherical nose cone has a different geometry and configuration to that of the right cone 10. The hemispherical nose cone 200 includes all of the broad features of the right cone 10 providing the hemispherical nose cone 200 with drag resistance properties under supersonic flow conditions. As such, features of the hemispherical nose cone 200 that are similar to those of the right cone 10 are designated by similar reference numerals in the drawings. Figures 22A - 22D show three-dimensional, sectioned three-dimensional, sectioned side and front end views, respectively, of an aerodynamic structure in accordance with the invention, in the form of a secant ogive nose cone designated generally by the reference numeral 300. The secant ogive nose cone 300 is similar to the right cone 10 with the only difference being that the secant ogive nose cone has a different geometry and configuration to that of the right cone 10. The secant ogive nose cone 200 includes all of the broad features of the right cone 10 providing the secant ogive nose cone 200 with drag resistance properties under supersonic flow conditions. As such, features of the secant ogive nose cone 200 that are similar to those of the right cone 10 are designated by similar reference numerals in the drawings.

[0078] Figures 23A - 23D show three-dimensional, sectioned three-dimensional, sectioned side and front end views, respectively, of an aerodynamic structure in accordance with the invention, in the form of an ellipsoid nose cone designated generally by the reference numeral 400. The ellipsoid nose cone 400 is similar to the right cone 10 with the only difference being that the ellipsoid nose cone has a different geometry and configuration to that of the right cone 10. The ellipsoid nose cone 400 includes all of the broad features of the right cone 10 providing the ellipsoid nose cone 400 with drag resistance properties under supersonic flow conditions. As such, features of the ellipsoid nose cone 400 that are similar to those of the right cone 10 are designated by similar reference numerals in the drawings.

[0079] It will be appreciated that the number, dimensions, configuration and arrangement of the air intake apertures, of the air inlet passages and of the air outlet passages may vary considerably while still embodying and incorporating the general principles of the aerodynamic structures defined and described above. As such, the air inlet and the air outlet passages may have variable internal dimensions and shapes and may include linear, non-linear, helical oval, spiral and uneven configurations and non-constant internal profiles. The air inlet passages and the air outlet passages may also have smooth or rough internal surfaces. It is also contemplated that the air inlet passage may comprise one type of passage, for example, longitudinal passages only. The specific non-limiting examples provided herein should therefore not be construed as limiting the scope of the invention as defined herein.

Claims

CLAIMS:

1. An aerodynamic structure which is exposed to airflow at supersonic speeds, the aerodynamic structure including:A) an aerodynamic outer surface over which air flows;B) an air intake arrangement comprising: b1) a plurality of air intake apertures defined in the aerodynamic outer surface at a forward section thereof; b2) a network of air inlet passages wherein each air inlet passage extends inwardly from a particular one of the intake apertures and terminates in a convergent nozzle section;C) an air venting arrangement comprising: c1) a plurality of air venting apertures defined in the aerodynamic surface at a rearward section thereof; and c2) a network of air outlet passages wherein each air outlet passage is in flow communication with the air inlet passages and has a divergent nozzle section adjacent the air inlet passage and terminates at a particular one of the air venting apertures for venting air therefrom; andD) a throat formation defined between each air inlet passage and an associated air outlet passage, at which airflow between the air inlet and outlet passages is momentarily choked.

2. The aerodynamic structure according to claim 1 , wherein the aerodynamic structure is in the form of a two-dimensional or three-dimensional body of revolution (BOR).

3. The aerodynamic structure, according to claim 1 or claim 2, wherein the convergent nozzle section of each air inlet passage, the divergent nozzle section of the air outlet passage associated therewith, and the throat formation defined between the convergent and divergent nozzle sections, together comprise a convergent-divergent nozzle formation.

4. The aerodynamic structure according to claim 3, wherein the configuration of the convergent-divergent nozzle formation is such that subsonic airflow enters the air intake passage where the converging geometry of the convergent nozzle section accelerates the airflow to choke at the throat formation where the mass flow reaches its maximum level, whereafter the airflow is accelerated by the diverging geometry of the divergent nozzle section to supersonic speeds where the airflow reaches its maximum speed at an outlet end of the divergent nozzle section.

5. The aerodynamic structure according to any one of claims 1 to 4, wherein the aerodynamic structure is in the form of a solid body comprising a conical structure having a front end at a narrow end of the conical structure and a rear end at a wider end of the conical structure, the aerodynamic structure including air inlet passage sections having a toroidal configuration.

6. The aerodynamic structure according to claim 5, wherein the air inlet passage sections are arranged in a series of spaced toroidal passage sections wherein centres of the air inlet passage sections coincide with a longitudinal cone axis extending through a centre of the conical structure.

7. The aerodynamic structure according to claims 6, wherein the toroidal passage sections conform to the geometry of the conical structure, with a forwardmost toroidal passage section having the smallest overall cross-sectional diameter, and a rearmost toroidal passage section having the largest overall cross-sectional diameter.

8. The aerodynamic structure according to claim 6 or claim 7, wherein cross- sectional diameters of the toroidal passage sections increase incrementally from the front end towards the rear end of the conical structure.

9. The aerodynamic structure according to any one of claims 6 to 8, wherein the toroidal passage sections are arranged in an equi-spaced arrangement within the conical structure.

10. The aerodynamic structure according to any one of claims 7 to 9, wherein the forwardmost toroidal passage section is located at a location about 25% from a tip of the conical structure, calculated along a length of the cone axis.

11. The aerodynamic structure according to any one of claims 7 to 10, wherein the rearmost toroidal passage section is located at a location about 90% from the tip of the conical structure, calculated along the length of the cone axis.

12. The aerodynamic structure according to any one of claims 6 to 11, wherein the spacing between the toroidal passage sections is approximately 1 mm.

13. The aerodynamic structure according to any one of claims 6 to 12, wherein the aerodynamic structure includes air inlet passage sections having a longitudinal configuration.

14. The aerodynamic structure according to claim 13, wherein the longitudinal passage sections intersect and are in flow communication with the toroidal passage sections in an arrangement wherein the longitudinal passage sections extend from the forwardmost toroid passage section to the rearmost toroid passage section.

15. The aerodynamic structure according to claim 14, wherein each longitudinal passage section passes through each toroidal passage section thereby linking the toroidal passage section to the longitudinal passage section.

16. The aerodynamic structure according to claim 14 or claim 15, wherein the longitudinal passage sections are arranged in a spaced arrangement around the cone axis.

17. The aerodynamic structure according to any one of claims 14 to 16, wherein the longitudinal passage sections have rectilinear configurations.

18. The aerodynamic structure according to any one of claims 14 to 17, wherein the longitudinal passage sections are inclined at an angle relative to the cone axis wherein the longitudinal passage sections are tapered towards the tip of the conical structure.

19. The aerodynamic structure according to claim 18, wherein the angle of inclination of the longitudinal passage sections is approximately 8 degrees.

20. The aerodynamic structure according to any one of claims 6 to 19, wherein the aerodynamic structure yet additionally includes air inlet passage sections having a radial configuration.

21. The aerodynamic structure according to claim 20, wherein the radial passage sections intersect and are in flow communication with the toroidal passage sections in an arrangement wherein the radial passage sections extend inwardly from the air intake apertures to the toroidal passage sections.

22. The aerodynamic structure according to claim 21, wherein each radial passage section extends inwardly from a particular one of the air intake apertures to a closest one of the toroidal passage sections, thereby linking the toroidal passage sections with the air intake apertures, thereby providing for re-distribution and dispersion of airflow entering the conical structure through the air intake apertures.

23. The aerodynamic structure according to claim 21 or claim 22, wherein the air intake apertures are arranged on the aerodynamic outer surface of the conical structure with a spacing between outer edges of the air intake apertures, of between 1 - 1 .5mm.

24. The aerodynamic structure as claimed in any one claims 21 to 23, wherein the air intake apertures comprise approximately 30% of the total outer surface of the conical structure.

25. The aerodynamic structure as claimed in any one of claims 20 to 24, wherein the air inlet passages have circular cylindrical profiles.

26. The aerodynamic structure according to any one of claims 5 to 25, wherein the air venting apertures are located at a rear section of the solid body, with the air outlet passages extending rearwardly between the toroidal passage sections and the air venting apertures.

27. The aerodynamic structure according to claim 26, wherein each air outlet passage extends between a particular one of the air venting apertures and the rearmost toroidal passage section.

28. The aerodynamic structure according to claim 27, wherein air outlet passages are arranged in an equi-spaced arrangement around the cone axis.

29. The aerodynamic structure as claimed in any one of claims 26 to 28, wherein the solid body includes a rear body structure at a rear end of the conical structure in which the air venting apertures are defined.

30. The aerodynamic structure as claimed in claim 29, wherein the rear body structure has a cylindrical configuration.

31. The aerodynamic structure as claimed in claim 29 or claim 30, wherein the air venting apertures are defined in the rear body structure, with the air outlet passages being arranged in a circumferential equi-spaced arrangement at an orientation of 45 degrees with respect to the cone axis.

32. The aerodynamic structure as claimed in any one of claims 6 to 22 when the claims depend at least from claims 6, 13 and 20, wherein the throat formations are defined at the junctures between the toroidal passage sections, the longitudinal passage sections and the radial passage sections and the air outlet passages associated therewith.

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