COMPONENT FOR MANIPULATING AN INPUT SHOCKWAVE

Abstract

A component for manipulating an input shockwave. The component includes a body comprising a first material. The body defines a cavity for manipulating the input shockwave so to produce a manipulated shockwave. The cavity comprises an input for receiving the input shockwave incident upon the component and an output for outputting the manipulated shockwave from the cavity. The cavity contains a second material having a shock-impedance that is lower than a shock-impedance of the first material.

Claims

1. A component for manipulating an input shockwave, wherein the component comprises: a body comprising a first material; wherein the body defines a cavity for manipulating the input shockwave so to produce a manipulated shockwave; wherein the cavity comprises: an input for receiving the input shockwave incident upon the component; and an output for outputting the manipulated shockwave from the cavity; and wherein the cavity contains a second material having a shock-impedance that is lower than a shock-impedance of the first material.

2. The component as claimed in claim 1, wherein the body is shaped such that a cross-sectional area of the input is greater than a cross-sectional area of the output.

3. The component as claimed in claim 1, wherein the cavity comprises a frustum.

4. The component as claimed in claim 1, wherein the cavity comprises a conic frustum

5. The component as claimed in claim 1, wherein the cavity comprises two or more sections that are at different respective angles to the axis of the cavity.

6. The component as claimed in claim 1, comprising one or more impedance matching layers.

7. The component as claimed in claim 6, wherein the one or more impedance matching layers comprises an input impedance matching layer adjacent to the input of the cavity, wherein the input impedance matching layer comprises a planar layer of a material having a shock-impedance that is greater than the shock-impedance of the second material.

8. The component as claimed in claim 6, wherein the one or more impedance matching layers comprises an output impedance matching layer adjacent to the output of the cavity, comprising a planar layer of a material having a shock-impedance that is less than the shock-impedance of the second material.

9. The component as claimed in claim 1, wherein the cavity is partially filled with the second material.

10. The component as claimed in claim 1, wherein the cavity contains a plurality of layers, wherein one or more of the plurality of layers comprises the second material.

11. The component as claimed in claim 10, wherein the plurality of layers comprises at least one first layer and at least one second layer, wherein the at least one first layer comprises a third material, and the at least one second layer comprises the second material.

12. The component as claimed in claim 11, wherein the third material has a higher shock-impedance than the shock-impedance of the second material.

13. The component as claimed in claim 11, wherein the plurality of layers alternate between least one first layer and the least one second layer.

14. The component as claimed in claim 1, wherein the cavity comprises a first sub-cavity and a second sub-cavity arranged between the input of the cavity and the output of the cavity, wherein the first sub-cavity comprises an input and an output, and the second sub-cavity comprises an input and an output, wherein the output of the first sub-cavity is coupled to the input of the second sub-cavity.

15. The component as claimed in claim 14, wherein the body is shaped such that a cross-sectional area of the output of the first sub-cavity is less than a cross-sectional area of the input of the second sub-cavity.

16. The component as claimed in claim 15, wherein the cavity comprises a plurality of sub-cavities, wherein each sub-cavity comprises an input and an output, wherein the output of each sub-cavity is coupled to the input of the subsequent sub-cavity, wherein the body is shaped such that a cross-sectional area of the output of each sub-cavity is less than a cross-sectional area of the input of the subsequent sub-cavity.

17. The component as claimed in claim 14, wherein the cavity comprises a layer between the first and second sub-cavities.

18. A component as claimed in claim 1, wherein the cavity comprises a spacing between the input of the cavity and an input surface of the second material.

19. A component for manipulating an input shockwave, wherein the component comprises: a body comprising a first material; wherein the body defines a cavity for manipulating the input shockwave so to produce a manipulated shockwave; wherein the cavity comprises: an input for receiving the input shockwave incident upon the component; an output for outputting the manipulated shockwave from the cavity; and a plurality of layers between the input and the output; wherein the plurality of layers comprises one or more layers comprising a second material having a shock-impedance that is lower than a shock-impedance of the first material.

20. A component for manipulating an input shockwave, wherein the component comprises: a body comprising a first material; wherein the body defines a cavity for manipulating the input shockwave so to produce a manipulated shockwave; wherein the cavity comprises: an input for receiving the input shockwave incident upon the component; an output for outputting the manipulated shockwave from the cavity; a first sub-cavity and a second sub-cavity arranged between the input of the cavity and the output of the cavity; wherein the first sub-cavity comprises an input and an output, and the second sub-cavity comprises an input and an output; wherein the output of the first sub-cavity is coupled to the input of the second sub-cavity.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0116] Certain embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0117] FIG. 1 shows a component in accordance with one embodiment of the invention;

[0118] FIG. 2 shows a system incorporating the component of FIG. 1;

[0119] FIGS. 3a and 3b show variants of the embodiment of FIG. 1 comprising impedance matching layers;

[0120] FIGS. 4a-f show six successive stages of an interaction of a shockwave with the component shown in FIG. 3a;

[0121] FIG. 5 shows a variant of the embodiment of FIG. 1;

[0122] FIG. 6 shows a component in accordance with another embodiment of the invention;

[0123] FIG. 7 shows an embodiment of a component comprising the features of the embodiment of FIG. 1 and the embodiment of FIG. 6;

[0124] FIG. 8 shows a perspective cutaway view of a variant of the embodiment of FIG. 7

[0125] FIG. 9 shows a variant of the embodiment of FIG. 7 comprising a vacuum layer;

[0126] FIG. 10 shows a variant of the embodiment of FIG. 7;

[0127] FIG. 11 shows a variant of the embodiment of FIG. 1;

[0128] FIG. 12 shows a variant of the embodiment of FIG. 7;

[0129] FIG. 13 shows a variant of the embodiment of FIG. 1.

DETAILED DESCRIPTION

[0130] Components for producing localized energy concentrations from an input shockwave will now be described.

[0131] FIG. 1 shows a cross section through a component 1 in accordance with one embodiment of the invention. The component 1 comprises a body 3 that defines a hollow frustum shaped cavity 5. The body 3 is formed of a material having a high shock-impedance. In an exemplary embodiment, the body 3 is formed of tantalum.

[0132] The body may be formed of other materials, for example other heavy metals, e.g., tungsten, steel, copper or platinum.

[0133] The cavity 5 contains a material 7 having a low shock-impedance. The cavity fill material 7 has a lower shock-impedance than that of the body 3. In an exemplary embodiment, the cavity fill material 7 is polymethyl methacrylate (PMMA).

[0134] The cavity 5 has an input aperture 9 that is configured to receive a shockwave, and an output aperture 11 that is configured to output the shockwave after the shockwave has propagated through the component 1. The cross-sectional area of the input aperture 9 is greater than that of the output aperture 11.

[0135] FIG. 1 shows a cross section through the component, in a plane containing a longitudinal axis of the component, the longitudinal axis extending perpendicularly between the plane of the input aperture 9 and the plane of the output aperture 11.

[0136] In the illustrated embodiment, the component 1 is rotationally symmetrical about the longitudinal axis. It will therefore be understood that the cavity 5 of the component 1 is shaped as a conic frustum with an input radius greater than the output radius. The component 1 has an input face 10 which is proximal to the input 9 of the cavity 5, and an output face 12 which is proximal to the output 11 of the cavity 5.

[0137] Operation of the component 1 will now be explained with reference to FIG. 2. The input 9 is configured to receive a shockwave. In the embodiment shown in FIG. 2, this shockwave is generated by striking the input face 10 of the component 1 with a diskshaped projectile 13. This strike generates a planar shockwave in the component 1 which is focused by the component 1 onto a target 15, creating a localized concentration of energy at the location of the target 15.

[0138] FIG. 3a shows an embodiment of the component 1 having an impedance matching layer 17 provided on the input face 10 of the component 1. The impedance matching layer 17 is a planar layer of material having a shock-impedance which is between that of the projectile 13, and that of the cavity fill material 7. The impedance matching layer 17 improves the coupling efficiency into the component 1 such that a higher proportion of the energy input into the component 1 by the projectile 13 is transmitted into the cavity fill material 7.

[0139] In embodiments, the impedance matching layer 17 may be formed of a material having a variable shock-impedance, such as a high impedance foam. The first shock will encounter a relatively low impedance material, but will compress the foam such that aftershocks then encounter a compressed, and hence high-impedance material. Such an impedance matching layer 17 may allow a low-impedance projectile 13 to be used since the low-impedance projectile may effectively couple to the foam.

[0140] FIG. 3b shows an embodiment of the component 1 having both a first impedance matching layer 17 provided on the input face 10 of the component 1, and a second impedance matching layer 19 provided on the output face 12 of the component 1. The second impedance matching layer 19 is a planar layer of material having a shock-impedance which is between that of the cavity fill material 7, and that of the target 15. In embodiments, the second impedance matching layer 19 is formed of polymethylpentene, e.g., TPX.

[0141] Operation of the component 1 will now be further explained with reference to FIGS. 4a-e. FIGS. 4a-e show a projectile 13 striking the component 1 shown in FIG. 4a. FIG. 4a shows the projectile 13 striking the impedance matching layer 17. At FIGS. 4b, and 4c, a resulting shockwave 20 passes through the impedance matching layer 17, and enters the cavity fill material 7. Pressures are increased in the component 1 through shockwave reflection and superposition within the cavity 5.

[0142] On input into the cavity 5, the input shock reflects from the cavity walls 6, as seen in FIG. 4d, as an irregular shock reflection (Mach reflection), that propagates in from the cavity walls 6, eventually overlapping on the central axis of the cavity 5 as shown in FIG. 4e and FIG. 4f. The overlap of this radially-symmetric wave on the central axis creates a high pressure point within the cavity fill material 7, which expands and interacts with the impinging Mach reflection, leading to the generation of an axial, quasi-planar Mach stem that propagates towards the output 11 of the cavity 5. This wave eventually reaches the output 11 of the cavity 5 and emerges from the component 1 with a higher pressure than that of the original input shockwave 20.

[0143] In simulations, a component in line with the embodiment of FIG. 1 achieved a pressure multiplication factor of 8.5, with an input shockwave having a pressure of 74 GPa, and an output shockwave having a pressure of 630 GPa.

[0144] FIG. 5 shows a variant of the embodiment shown in FIG. 1 in which the cavity 5 has the shape of a flared conic frustum, with a cavity wall 6 which is elliptically curved. Other than the cavity shape, the structure of the component 1 is as described above in relation to FIG. 1. This different shape may alter the output shock profile and shock state, but the basic function of the cavity 5 is as described above in relation to FIGS. 4a-e.

[0145] FIG. 6 shows a component 101 according to another embodiment of the invention. The component 101 comprises a body 103 formed of a series of parallel layers. The layers comprise low shock-impedance layers 130 formed of a low shock-impedance material such as PMMA or epoxy resin, and high shock-impedance layers 132 formed of a high shock-impedance material such as tantalum, platinum, tungsten, steel, copper, or other (e.g., heavy) metals. As a minimum requirement, the high shock-impedance layers 132 is formed of a material having a higher shock-impedance than the material forming the low shock-impedance layers. In preferred embodiments, the ratio of the shock-impedance of the high shock-impedance layers to the shock-impedance of the low shock-impedance layers is high such that there is a large shock-impedance difference at the boundary between layers.

[0146] The parallel layers alternate from low shock-impedance layers 130 to high shock-impedance layers 132 from one layer to the next. In the illustrated embodiment, an input layer 134 which forms the input face 110 of the component 101 is a low shock-impedance layer 130. This is because an input face 110 formed from a high shock-impedance layer 132 would result in a larger portion of the shockwave being reflected by the input face 110, and hence not transmitted into the component 101. The alternative is however envisaged, and an input face 110 formed from a high shock-impedance layer 132 may help to better couple the shock into the component 101 since a high shock-impedance layer may have a more similar shock-impedance to that of a projectile 13 striking the component.

[0147] In the illustrated embodiment, the high shock-impedance layers 132 are each of equal thickness, whilst the low shock-impedance layers have thicknesses that decrease progressively from the input face 110 to the output face 112. In embodiments however, the thicknesses of the high shock-impedance layers 132 may also decrease progressively from the input face 110 to the output face. It will be understood that although the thickness may vary between layers, each individual layer has a uniform thickness across its width.

[0148] The layers are arranged such that shockwaves generated at the input face 110 of the component 101 of the layer stack reverberate within the stack of layers, as a result of reflections from the boundaries between low and high shock-impedance layers 130, 132, leading to regions of constructive and destructive interference as shock waves pass over one another. When a shock passes from a low shock-impedance layer 130 into a high shock-impedance layer 132, a portion of the shock is transmitted into the high shock-impedance layer 132 whilst a portion is reflected back into the low shock-impedance layer 130.

[0149] The portion in the low shock-impedance layer 130 speeds up since it is now travelling through pre-shocked material, the shock portion then reflects from the boundary at the input of the low shock-impedance layer, and since it has been sped up, the reflected portion eventually catches up with the portion of the shock that was initially transmitted into the high shock-impedance layer 132. Through the arrangement of the low and high shock-impedance layers 130, 132, the component 101 can be arranged such that a plurality of shock portions superimpose on the output face 112 of the component 101, leading to a short-lived high shock pressure state that can be passed into a target adjacent to the component output 112.

[0150] In the illustrated embodiment, all of the high shock-impedance layers 132 are formed from the same material, and all of the low shock-impedance layers 130 are formed from the same material. In embodiments, different low shock-impedance materials may be used for the different low shock-impedance layers 130, and different high shock-impedance materials may be used for the different high shock-impedance layers 132.

[0151] FIG. 7 shows a component 201 according to another embodiment of the invention, encompassing features from both the embodiment of FIG. 1, and the embodiment of FIG. 6. The component 201 comprises a body 203 which defines a hollow conic frustum shaped cavity 205. The body 203 is formed of a material having a high shock-impedance. The cavity 205 contains a material 207 having a low shock-impedance. The cavity fill material 207 has a lower shock-impedance than that of the body 203. Within the cavity 205, a plurality of parallel high shock-impedance layers 232 are provided.

[0152] In the illustrated embodiment, the high shock-impedance layers 232 are formed as plates which span the cross-sectional area of the component 201. The body 203 itself is therefore formed of layers, each layer defining a frustum shaped sub-cavity 250. In embodiments however, the high shock-impedance layers 232 may only span the cavity 205 such that the body 203 may be formed as a single piece. The cavity 205 has an input 209 which is configured to receive a shockwave, and an output 211 which is configured to output the shockwave after the shockwave has propagated through the component 201. The cross-sectional area of the input 209 is greater than that of the output 211.

[0153] FIG. 7 shows a vertical cross section, but in the illustrated embodiment, the component 201 is rotationally symmetrical. It will therefore be understood that the cavity 205 of the component 201 is shaped as a conic frustum with an input radius greater than the output radius, as can be more clearly seen from the perspective cut-through view of a variant of the embodiment shown in FIG. 8. The component 201 itself has an input face 210 which is proximal to the input 209 of the cavity 205, and an output face 212 which is proximal to the output 211 of the cavity 205.

[0154] The cavity 205 is filled with low shock-impedance layers 230 which are formed from the low shock-impedance cavity fill material 207 (PMMA in the illustrated embodiment), and high shock-impedance layers 232 formed from the high shock-impedance material (tantalum in the illustrated embodiment) plates. As a minimum requirement, the high shock-impedance layers 232 is formed of a material having a higher shock-impedance than the material forming the low shock-impedance layers 230.

[0155] The parallel layers alternate from low shock-impedance layers 230 to high shock-impedance layers 232 from one layer to the next. In the illustrated embodiment, an input layer 234 which forms the input face 210 of the component 201 is a low shock-impedance layer 230. This is because an input face 210 formed from a high shock-impedance layer 232 would result in a larger portion of the shockwave being reflected by the input face 210, and hence not transmitted into the component 201.

[0156] In the illustrated embodiment, the high shock-impedance layers 232 are each of equal thickness, whilst the low shock-impedance layers 230 have thicknesses that decrease progressively from the input face 210 to the output face 212. It will be understood that although the thickness may vary between layers, each individual layer has a uniform thickness across its width.

[0157] The integration of the focusing shape of the frustum shaped cavity 205 with the parallel layers 230, 232 leads to a component design which has been shown to be capable of greatly increasing shock pressures on output, relative to either of the features individually. Shock reflections from the walls of the cavity 205 interact with axial shock reflections from the high shock-impedance layers 232, creating regions of locally high thermodynamic pressure. These high-pressure regions expand and interact with further shock reflections downstream in the component 201, creating regions with yet-higher shock pressure, that eventually pass through to the output 211 of the cavity 205.

[0158] When a shock passes from a low shock-impedance layer 230 into a high shock-impedance layer 232, a portion of the shock is transmitted into the high shock-impedance layer 232 whilst a portion is reflected back into the low shock-impedance layer 230. The portion in the low shock-impedance layer 230 speeds up since it is now travelling through pre-shocked material, the shock portion then reflects from the boundary at the input of the low shock-impedance layer 230, and since it has been sped up, the reflected portion eventually catches up with the portion of the shock that was initially transmitted into the high shock-impedance layer 232. The shockwave is also tangentially focused by the cavity walls 6.

[0159] Through configuration of the parallel layer materials and thicknesses, as well as the shape of the cavity 205, it is possible to control the pressure of the shock at the output 211, as well as the uniformity of the shock state and shape. It will be understood that although the thickness may vary between layers, each individual layer has a uniform thickness across its width.

[0160] In addition to generating the conditions for local shock superposition and constructive interference, the parallel layers 230, 232 also act to effectively slow the shock transit time through the component 201. This allows energy from more of the projectile 13 to be harvested and combined into a single shock state upon emergence from the component 201.

[0161] FIG. 8 shows a cut-through perspective view of a variant of the embodiment of FIG. 7 in which the thickness of the high shock-impedance layers 232 also decreases from the input 209, to the output 211. FIG. 8 clearly illustrates the plate structure of the component 201.

[0162] Simulations and experiments have shown that a pressure multiplication factor of at least 15 is achievable for an input-radius/exit-radius ratio of 8.9 for a component design in line with the embodiment of FIG. 8. For example, in simulations, with an input shockwave having a pressure of 83 GPa, an output pressure of 1240 GPa was achieved.

[0163] FIG. 9 shows a variant of the embodiment of FIG. 7, wherein the layer 333 at the input 309 is vacuum. In embodiments, the layer 333 may not be vacuum, and may instead contain a gas. The first non-vacuum filled layer 335 in the cavity 305 is preferably a low shock-impedance layer 330 because a first non-vacuum filled layer 335 formed from a high shock-impedance layer 332 would result in a larger portion of the shockwave being reflected by the first non-vacuum filled layer 335, and hence not transmitted into the rest of the component 301. However, the alternative is also envisaged.

[0164] In the embodiment of FIG. 9, the impacting projectile 13 only strikes the body 303 of the component 301 directly. This leads to the generation of an axially converging shock reflection within the projectile 13, that passes into the cavity fill material 307 when the front face of the projectile 13 contacts the first non-vacuum filled layer 335. These transmitted-reflected shocks subsequently superimpose on the central axis within the cavity 305, leading to the generation of a high pressure state that expands as a Mach stem towards the output 311. It is preferable that the projectile 13 is smaller than the cavity input 309 such that the edges of the projectile first strike the cavity wall 6. The function of the cavity 305 and the subsequent parallel layers 330, 332, is as described above in relation to FIG. 7.

[0165] In simulations, a component in line with the embodiment of FIG. 9 has achieved a pressure multiplication factor of 5, with an input shockwave having a pressure of 140 GPa, and an output shockwave having a pressure of 700 GPa.

[0166] FIG. 10 shows a variant of the embodiment of FIG. 7 in which the cavity 405 has a different shape. As in the embodiment of FIG. 7, the body 403 is formed of a plurality of layers, each layer defining a frustum shaped sub-cavity 450 having an input 4509 and an output 4511. In the illustrated embodiment, each sub-cavity is a conical frustum, but other shapes are considered. In the embodiment of FIG. 10, the cross-sectional area of the input 4509 of each sub-cavity 450 is greater than the cross-sectional area of the output 4511 of the preceding sub-cavity. In conical frustum embodiments, this means that the radius of the input 4509 of each sub-cavity is greater than the radius of the output 4511 of the preceding sub-cavity.

[0167] The component 401 shown in FIG. 10 functions in substantially the same way as described above in relation to FIG. 7, but the overlapping outputs 4511 and inputs 4509 enables shocks that are transmitted from the cavity fill material 407 of a sub-cavity 450 into the body 403 of the component 401 to be partially recaptured by the input 4509 of the subsequent sub-cavity 450, and focused back into the cavity fill material 407 contained in that sub-cavity. This may lead to a reduced amount of shock loss and hence a more efficient component 401. Further, since the sub-cavities 450 are discrete, the different sub-cavities 450 can have different properties such as input diameter, output diameter, thickness, material, and sub-cavity wall angle. It will be understood that although the thickness may vary between layers, each individual layer has a uniform thickness across its width.

[0168] FIG. 11 shows a variant of the embodiment of FIG. 1 in which the cavity wall 406 of the component 401 is coated with a barrier 421 which has a shock-impedance between that of the cavity fill material 407, and that of the body 403. In the illustrated embodiment, the barrier 421 is formed of aluminium, the cavity fill material 407 is a PMMA, and the body 403 is formed of tantalum, although other materials are considered. The thickness of the barrier 421 decreases from the cavity input 409, to the cavity output 411, however in other embodiments, the barrier 421 may have a uniform thickness. The barrier 421 may be formed as a frustoconical insert. The barrier 421 has a thickness which is an order of magnitude less than the diameter of the cavity 405. As such, the barrier 421 has a thickness between 0.1 mm and 1 mm. The barrier 421 acts as a waveguide to direct the shockwave towards the cavity output 411 rather than into the cavity wall 406.

[0169] FIG. 12 shows a variant of the embodiment of FIG. 7. The component 501 comprises a buffer 523 between the edges of the parallel layers 530, 532, and the cavity wall 506. The buffer 523 is formed of a low density material such as PMMA or epoxy resin, and may be formed of the same material as the low shock-impedance layers 532. The buffer 523 may help to reflect the shocks from the cavity wall 506.

[0170] FIG. 13 shows a variant of the embodiment of FIG. 1. The component 801 cavity 805 contains a frustoconical element 827, formed of a plastic material such as PMMA or epoxy resin, which is separated from the cavity wall 806 by a vacuum gap 828. As a projectile 13 strikes the body 803 and the frustoconical element 827, the vacuum gap 828 closes due to the deformation of the body 803 and the frustoconical element 827. The closure of the vacuum gap 828 drives a shock into the element 827. The shock may travel faster in the body 803 due to its higher density, and hence the body 803 may be pre-compressed by the shock. This pre-compression of the body increases its shock-impedance which helps to better focus the shock in the element 827 towards the cavity output 811 since the shock will be reflected from the cavity wall 806.

[0171] Although specific examples have been given, it will be appreciated that there are a large number of parameters that influence the actual results achieved.

[0172] In each of the embodiments described above, the diagrams shown are a vertical cross-section through a three-dimensional component and hence they depict embodiments that are rotationally symmetric. However, this is not essential to the invention.

[0173] It will be understood that the embodiments explicitly disclosed herein are intended to be exemplary, and the skilled person will understand that features of the embodiments disclosed herein may, except where mutually exclusive, be combined in combinations not explicitly mentioned in order to form new embodiments.

[0174] Embodiments of the invention may be suitable for amplifying shockwaves for the purpose of generating conditions suitable for nuclear fusion. However, the invention is not limited to this, and may be used for other applications, for example, the testing of safety equipment such as crash helmets. In one specific example, the invention could be used to provide an impact shockwave for testing the impact force dampening and defusing structure shown in U.S. Pat. No. 10,653,193 B2.

[0175] Further, although the specific embodiments disclosed herein are configured to achieve a flat pressure pulse output, some applications may require different pulse shapes, and components in accordance with the invention may be configured (via their geometry, and the arrangement of any layers present) to provide differently shaped output pressure pulses.