Structure with rigid projections adapted to traverse a fluid environment

Abstract

A structure adapted to traverse a fluid environment includes an elongate body having a root, a wingtip, a leading edge and a trailing edge; and a plurality of rigid projections each extending from a respective position along the leading edge and/or the trailing edge generally along the same plane as a front surface of the body.

Claims

1. A structure adapted to traverse a fluid environment, the structure comprising: an elongate body having a root, a wingtip, a leading edge and a trailing edge; and a plurality of rigid projections each extending from a respective position along the trailing edge generally along the same plane as a front surface of the body wherein the projections include a first and a second set of projections extending from the trailing edge, each projection of the plurality of projections having a length, and wherein the projections of the first set and the second set of projections are discrete projections that alternate with one another extending along the trailing edge; wherein the lengths of adjacent projections extending from the trailing edge differ from one another; and wherein the lengths of adjacent projections of the first set and the second set differ from one another at half a wavelength distance of a target sound frequency.

2. The structure of claim 1, where in the rigid projections extend towards the wingtip.

3. The structure of claim 2, wherein the rigid projections and the elongate body are connected to each other.

4. The structure of claim 1, wherein the projections extend from a portion of the leading edge that is less than the entire span of the leading edge.

5. The structure of claim 4, wherein the rigid projections extend from the leading edge from between about 40% and 96% of the elongate body, where the root of the rotor blade represents 0% and the wingtip represents 100%.

6. The structure of claim 1, wherein the projections of the first set and the projections of the second set interacting with incident air flow on the trailing edge to cause destructive interference of sound waves generated from the leading edge interacting with the incident air flow.

7. The structure of claim 1, wherein the structure is a rotor blade.

8. A turbine comprising at least one rotor blade as recited in claim 7.

9. The rotor blade of claim 1, wherein a different configuration of projections on the trailing edge is applied as opposed to the leading edge.

10. The rotor blade of claim 9, wherein the leading edge has projections of larger surface area as compared to the trailing edge.

11. A rotor blade, wherein the rotor blade defines an aerodynamic body having a pressure side, suction side, leading edge, trailing edge and blade tip, the blade body further comprising: a plurality of projections extending from the aerodynamic body in the vicinity of the trailing edge applied in the range of 40-96% of the rotor blade, where the root of the rotor blade represents 0% and the blade tip represents 100% the projections having an alternating length and width and being non-uniform in dispersement; a generally decreasing length and width respective to these projections moving towards the blade tip; a flexible or rigid and/or curvilinear or linear architecture; a composition of biologically or non-biologically based materials; wherein the length of each of the plurality of projections is approximately parallel to a local flow streamline defined for that projection; wherein the rigid projections that may be curvilinear are in the line of the arc of local flow streamline defined for that projection; and where it may be made of a material with a coefficient of linear thermal expansion (CLTE) between 1.010.sup.4 m/m C. and 7.010.sup.4 m/m C.; wherein the projections of the first set and the second set of projections are discrete projections that alternate with one another extending along the trailing edge and the corresponding length of each projection of the projections is inversely correlated with a distance from the root; wherein the lengths of adjacent projections extending from the trailing edge differ from one another; and wherein the lengths of adjacent projections of the first set and the second set differ from one another at half a wavelength distance of a target sound frequency, the projections of the first set and the projections of the second set interacting with incident air flow on the trailing edge to cause destructive interference of sound waves generated from the leading edge interacting with the incident air flow.

12. The rotor blade of claim 11, wherein the projections are applied in the region of the trailing edge only.

13. The rotor blade of claim 11, wherein the projections are applied in the region of the leading edge only.

14. The rotor blade of claim 11, wherein the projection has a configuration selected from the group consisting of: a serration, brush, comb, riblet, fluting, fimbriae.

15. A wind turbine comprising a rotor blade as recited in claim 11.

16. A method for increasing the efficiency and/or decreasing the noise emissions of an operating wind turbine comprising a hub and rotor blade(s), wherein at least one rotor blade is connected to the hub and is defined by an aerodynamic body having a pressure side, suction side, leading edge, trailing edge and blade tip, the method comprising: mounting a plurality of projections on the aerodynamic body that extend in the vicinity of the trailing edge, the applied projections in the range of 40-96% of the rotor blade, where the root of the rotor blade represents 0% and the blade tip represents 100%; alternating the length and width respective to these projections; wherein the length of the longer projection is longer than an adjacent projection by the wavelength of the sound wave at a given temperature; wherein the projections, as the projections travel through a fluid, create a sound wave of a certain wavelength that corresponds with a neighboring sound wave emitted by a component of the rotor blade that elicits destructive interference of the neighboring sound waves.

17. The method of claim 16, wherein the projections are made from a fibrous material that is embedded within a matrix.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures wherein:

(2) FIG. 1 is a side elevation view of a horizontal axis wind turbine, according to the prior art;

(3) FIG. 2 is a front perspective view of one of the rotor blades of the wind turbine of FIG. 1, in isolation;

(4) FIG. 3 is a front perspective view of a structure in accordance with an embodiment of the invention, in isolation;

(5) FIG. 4 is a perspective cross-sectional view of the trailing edge of a structure having various trailing edge projections;

(6) FIG. 5A is a perspective cross-sectional view of the trailing edge of a structure having various trailing edge projections;

(7) FIG. 5B is a perspective cross-sectional view of the trailing edge of a structure having various trailing edge projections;

(8) FIG. 6 is a perspective cross-sectional view of the trailing edge of a structure having various leading edge projections;

(9) FIG. 7 illustrates a top plan view of the trailing edge of a structure showing various projections and their respective lengths;

(10) FIG. 8 illustrates a side elevation view of a sound wave emitted from a trailing edge projection of a structure, including destructive interference of the sound wave; and

(11) FIG. 9 illustrates two side elevation views of respective sound waves of varying frequency within the range of those emitted from a trailing edge of a structure such as a wind turbine rotor blade.

DETAILED DESCRIPTION

(12) Reference will now be made in detail to the various embodiments of the invention, one or more examples of which are illustrated in the figures. Each example is provided by way of explanation of the invention, and is not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the present invention includes such modifications and variations.

(13) The present patent application includes description of opportunities for improving on the traditional aspects of a blade configuration for a wind turbine. The present patent application yields to a blade configuration with unique biologically-inspired projections that can conveniently be retrofitted onto the blade portion as desired, and which create destructive interference so that the emitted sound waves are decreased, thus increasing the overall efficiency of the wind turbine.

(14) FIG. 1 is a side elevation view of a horizontal axis wind turbine 10, according to the prior art. Wind turbine 10 includes a tower 100 supported by and extending from a surface S, such as a ground surface. Supported by tower 100, in turn, is a nacelle 200 extending horizontally. A hub with a spinner 300 is rotatably mounted at a front end of nacelle 200 and is rotatable with respect to nacelle 200 about a rotation axis R. Spinner 300 receives and supports multiple rotor blades 400 that each extend outwardly from spinner 300. Rotor blades 400 catch incident wind W, flowing towards the wind turbine 10 and are caused to rotate. Due to their being supported by spinner 300, rotor blades 400 when rotating cause spinner 300 to rotate about rotation axis R thereby to cause rotational motion that can be converted in a well-known manner into usable electrical or mechanical power. In this sense, rotor blades 400 are each structures adapted to traverse a fluid environment, where the fluid in this embodiment is ambient air. Nacelle 200 may be rotatably mounted to tower 100 such that nacelle 200 can rotate about a substantially vertical axis (not shown) with respect to tower 100, thereby to enable rotor blades 400 to adaptively face the direction from which incident wind W, is approaching wind turbine 10. A nose cone 500 of generally a uniform paraboloidal shape is shown mounted to a front end of spinner 300 to deflect incident wind W, away from spinner 300.

(15) FIG. 2 is a front perspective view of one of rotor blades 400 in isolation. Rotor blade 400 includes an elongate body that extends from a root 410 through a main section 412 to terminate at a wingtip 414. Root 410 extends from nacelle 200 when attached thereto or integrated therewith, whereas wingtip 414 is the portion of the elongate body that is distal to nacelle 200. The elongate body has a leading edge 420 and a trailing edge 430, where leading edge 420 leads trailing edge 430 when rotor blade 400 is in motion rotating with nacelle 200 about rotation axis R in the direction D. A suction side 440 of the elongate body is shown in FIG. 2, and a pressure side 450, shown in dotted lines, is opposite the elongate body from suction side 440.

(16) FIG. 3 is a front perspective view of a structure 400A in accordance with an embodiment of the invention, in isolation. A detailed perspective view of the structure 400A defines an aerodynamic body having a pressure side 440, a suction side 450, a leading edge 420, a trailing edge 430 and wingtip 414, the blade body further comprising an application in the range of 40-96% 139 of the rotor blade, where the root of the rotor blade represents 0% 140 and the blade tip represents 100% 141. Two regions outlined at the leading edge 145 and trailing edge 150 show the possible areas of attachment for the projections.

(17) FIG. 4 illustrates a perspective cut-away view of the trailing edge 150 of a wind turbine rotor blade showing various flexible or rigid projections of linear 151 or curvilinear 152 architecture as example. The curvilinear projections 152 are in the line of the arc of local flow streamline defined for that projection and the length of each of the plurality of projections is approximately parallel to a local flow streamline defined for that projection. The local flow streamline 153 is shown respective to the linear projection 151. The projections may be referred to as a comb, brush, serration, riblet, fluting or fimbriae and may be applied through a variety of methods. The projections have a generally decreasing length and width moving towards the blade tip 154.

(18) FIG. 5A illustrates other perspective cut-away view of the trailing edge 150 of a wind turbine rotor blade showing various projections 152b that are of a larger surface area than those of FIG. 4. The projections 152b may be integrally formed with the body of the blade at the trailing edge 137 during manufacture such that the projections 152b and the body of the trailing edge 137 are a unitary structure, or may alternatively be elements applied after formation of the blade body 137 to improve the operation of the wind turbine. In such an alternative construction, it is important that the flow of wind along the front surface of the blade be interrupted as little as possible due to the seams/discontinuities between the projections 152b and the body of the blade 137 at the point 150.

(19) FIG. 5B illustrates yet another perspective cut-away view of the trailing edge 150 of a wind turbine rotor blade showing various example projections, such as the brush 152c and serration 152d attached to the blade body 137. The brush 152c may preferentially resemble the plurality of projections extending from the trailing edge of the owl's wing. These projections are a tattered assembly of feathers of various lengths and sizes. The projections extending from the trailing edge of the blade may individually be of any length in relation to their diameter, and may be any thickness in relation to their length, such that the resulting action is beneficial to a decrease in noise emissions and/or an increase in efficiency for the wind turbine unit as a whole.

(20) FIG. 6 illustrates a perspective cut-away view of the leading edge 145 of a wind turbine rotor blade 130 showing various projections 155. These projections serve to break up the turbulence in the wind incident on the leading edge 145 into smaller groupings of micro-turbulences, thereby reducing the overall amount of noise emissions of the wind turbine, and increasing the efficiency of the wind turbine as a whole. The projections extending from the leading edge of the blade must be tapered, and must be spaced by at least their respective diameter and/or width 156, such that the resulting action is beneficial to a decrease in noise emissions and/or an increase in efficiency for the wind turbine unit as a whole. The projections 155 on the leading edge are different to the projections on the trailing edge, and may be larger as compared to those of FIG. 5, and may be applied to just the trailing edge only, or just the leading edge only. The projections 155 decrease in surface area towards the region of the wing tip 138, such that the projection 155a is larger than 155b. As can be seen in these projections, they may have a bulbous nature to them.

(21) The technical reasons for varying the lengths of neighbouring projections by various amounts are below explained with reference to FIGS. 7 through 9. These distances are based on the wavelengths of the sound waves produced at varying regions of the rotor blade, which is in turn based upon the velocity of the fluid at that point. FIG. 7 illustrates a top-down view of the trailing edge 150 of a wind turbine rotor blade showing various projections 151b and their respective lengths. These trailing edge projections alternate in length and width and are non-uniform in dispersement, as can be seen in the projections at 151b through to 151c. The difference in length 151d of neighbouring projections is based on the wavelength distance of the sound wave to be minimized.

(22) FIG. 8 illustrates the further reasoning of this distance, which is the wavelength of the sound wave to be minimized Here, you can see a side-on view of a sound wave 160 emitted from a trailing edge projection 151b of a wind turbine rotor blade of this invention, showing a method of destructive interference of the sound wave. According to an embodiment of this invention, the non-uniform lengths 151b, 151d are based upon the sound waves 160, 161 emanating from the various projections during the operation of the wind turbine.

(23) FIG. 8 further illustrates destructive interference, and the resulting sound wave 162 when this phenomenon occurs. FIG. 9 also illustrates a side-on view of two sound waves 160a, 160b of varying frequencies within the range of those emitted from the trailing edge of an operational wind turbine rotor blade. The wavelengths of the sound waves emitted decreases at you approach the blade tip, and thus varying lengths of projections are required. Here, this is illustrated in that wavelength 160a is longer than 160b, and would thus be emitted closer to the tip. These projections may be composed of biological or non-biologically based materials, where they are made of a materials with a coefficient of linear thermal expansion (CLTE) between 1.010.sup.4 m/m C. and 7.010.sup.4 m/m C., and more preferably 5.8710.sup.4 m/m C. This material may be made from a fibrous material that is embedded within a matrix. Where the fibrous material is biologically-based, it may include collagen, elastin, fibronectin, laminin, -chitin, -chitin, -keratin, -keratin, keratosulfate, cellulose, perlecan, agrin, mesoglea, keratin fibre soybean (KFS), chicken feather fibre (CFF) and/or polysaccharides, and exist in a matrix that may include acrylate epoxidized soybean oil (AESO) resin, polysaccharide-gels, water, glycosaminoglycans (GAGs) and/or proteoglycans. Where the fibrous material is not biologically-based, and may include glass-fibres, plastic-fibres, and/or carbon-fibres, and exists in a matrix that may include silicone, epoxy resin, and/or polyester resin. Further, where the fibres are biologically based, there may be a higher percentage of elastin-type fibres than collagen-type fibres and/or a higher percentage of matrix than fibres. Where the fibres are non-biologically based, there may be a higher percentage of matrix than fibres.

(24) Theoretical Considerations:

(25) The wavelength (w) of a given sound wave changes to a greater degree with temperature and to a lesser degree with elevation. Sound waves emitted and received below 5000 feet can be considered to be standard, and since most commercial wind farms are below this elevation, the present considerations will consider elevation to be of trivial importance with respect to the wavelength of sound. Temperature, however, has a greater effect on the wavelength of sound, and is represented in the graph below. The wavelength (w) of a given sound wave is determined by the product of the velocity (v) of the wave (which is dependent upon the temperature of the air) divided by the frequency (f), as in Equation 1 below:
w=v/f(1)

(26) Thus, with the speed of sound being about 340.276 meters per second (m/s) at 15 C. and below an altitude of 5000 feet, the wavelength of a sound wave of 1000 Hertz (Hz) is about 34 centimetres (cm), as shown in Equation 2 below:
w=340.276 m/s/1000 hz=34.028 cm(2)

(27) Sound emitted from wind turbine rotor blades varies with respect to the position of the airfoil that the flow streamline is passing over, respective to the axis of rotation, with areas further from this axis experiencing higher frequencies with higher local flow speeds. This scaling relationship increases by the fifth power (U.sup.5) of fluid velocity to noise intensity. Frequencies in and around 1 Khz have been described by listeners as sounding like a swooshing noise, with 2 Khz sounding like a humming noise and 20 Khz (the limit of human hearing) sounding like an ear-piercing ringing noise. Frequencies emitted by wind turbine rotor blades that generally fall into the frequency range of 1-20 Khz are the primary focus of this invention. As shown in Table 1 below, we can also see that the change wavelength increases on the order of forty (40) micrometers (m). The average change in wavelength with respect to temperature was determined to be 0.0587 cm. Therefore, an ideal material for this application would have a coefficient of linear thermal expansion (CLTE) of =5.8710.sup.4 m/m C.

(28) TABLE-US-00001 TABLE 1 Wavelength Change in (w) Temperature Speed of (cm) @ between it and the ( C.) Sound (m/s) 1 Khz following (w) 40 C. 354.730 m/s 35.473 cm 0.057 cm 39 C. 354.163 m/s 35.416 cm 0.056 cm 38 C. 353.596 m/s 35.360 cm 0.059 cm 37 C. 353.027 m/s 35.301 cm 0.055 cm 36 C. 352.457 m/s 35.246 cm 0.057 cm 35 C. 351.887 m/s 35.189 cm 0.058 cm 34 C. 351.316 m/s 35.131 cm 0.057 cm 33 C. 350.743 m/s 35.074 cm 0.057 cm 32 C. 350.17 m/s 35.017 cm 0.057 cm 31 C. 349.596 m/s 34.960 cm 0.058 cm 30 C. 349.02 m/s 34.902 cm 0.058 cm 29 C. 348.444 m/s 34.844 cm 0.057 cm 28 C. 347.867 m/s 34.787 cm 0.058 cm 27 C. 347.289 m/s 34.729 cm 0.058 cm 26 C. 346.710 m/s 34.671 cm 0.058 cm 25 C. 346.13 m/s 34.613 cm 0.058 cm 24 C. 345.549 m/s 34.555 cm 0.058 cm 23 C. 344.967 m/s 34.497 cm 0.059 cm 22 C. 344.384 m/s 34.438 cm 0.058 cm 21 C. 343.801 m/s 34.380 cm 0.058 cm 20 C. 343.216 m/s 34.322 cm 0.059 cm 19 C. 342.63 m/s 34.263 cm 0.059 cm 18 C. 342.043 m/s 34.204 cm 0.058 cm 17 C. 341.455 m/s 34.146 cm 0.059 cm 16 C. 340.866 m/s 34.087 cm 0.059 cm 15 C. 340.276 m/s 34.028 cm 0.061 cm 14 C. 339.685 m/s 33.967 cm 0.058 cm 13 C. 339.093 m/s 33.909 cm 0.059 cm 12 C. 338.50 m/s 33.850 cm 0.059 cm 11 C. 337.906 m/s 33.791 cm 0.060 cm 10 C. 337.311 m/s 33.731 cm 0.059 cm 9 C. 336.715 m/s 33.672 cm 0.060 cm 8 C. 336.118 m/s 33.612 cm 0.060 cm 7 C. 335.519 m/s 33.552 cm 0.060 cm 6 C. 334.920 m/s 33.492 cm 0.060 cm 5 C. 334.319 m/s 33.432 cm 0.060 cm 4 C. 333.718 m/s 33.372 cm 0.060 cm 3 C. 333.115 m/s 33.312 cm 0.061 cm 2 C. 332.512 m/s 33.251 cm 0.060 cm 1 C. 331.907 m/s 33.191 cm 0.061 cm 0 C. 331.301 m/s 33.130 cm 0.061 cm 1 C. 330.694 m/s 33.069 cm 0.060 cm 2 C. 330.086 m/s 33.009 cm 0.061 cm 3 C. 329.477 m/s 32.948 cm Average: 0.0587 cm

(29) As stated above, the preferred CLTE is =5.8710.sup.4 m/m C. This can be further derived from the equation of linear expansion of materials, as shown in Equation 3 below:
L=.Math.L.sub.o.Math.(TT.sub.o)(3) where: L is the increase in length; is the coefficient of linear expansion; L.sub.o is the original length; T.sub.o is the original temperature; and T is the temperature to which it is heated.

(30) Theoretical scaling laws for trailing edge noise have been established for some time. For example, the intensity of noise to low-speed air flow (>Mach 0.3) has the experimentally verified relation, as shown in Equation 4 below:

(31) $\begin{array}{cc}.Math.p^2.Math.\frac{{}_0^2}{c_0}\frac{U^{5}L}{r^2}D& \left(4\right)\end{array}$ where: p.sup.2 is the sound pressure intensity observed at a distance r from the trailing edge; .sub.o is the fluid density; c.sub.0 is the speed of sound; U is the fluid velocity in the vicinity of the edge; L is the span-wise extent of the flow (length of the blade section, for example); is a measure of the boundary layer thickness at the edge; and D is a directivity function that is a function of the angle of the observer to the edge.

(32) As can be seen, scaling of noise intensity to the fifth power (U.sup.5) highlights the role of aerodynamic noise as a design constraint for wind turbines. The local velocity over a blade section at radius R is UR, where rotational speed of the rotor. This speed can be up to 320 km/h at the tip. Given the U.sup.5 scaling relationship, a 15% increase in rotational speed would therefore increase noise by about 3 dB. Conversely, a 3 dB reduction in aerodynamic noise through design changes would allow for a 15% increase in turbine rotational speed. When coupled with blade structural design improvements, this increase in rotational speed can reduce system loads and enable lighter, cheaper rotor blades and drive trains.

(33) The above-described configurations of structures for traversing a fluid environment may be applicable in combination with one or more of the configurations disclosed in co-pending PCT Patent Application No. PCT/CA2015/050740 to Ryan Church, filed on even date, entitled STRUCTURE WITH RIGID WINGLET ADAPTED TO TRAVERSE A FLUID ENVIRONMENT, the contents of which are incorporated herein by reference, or in co-pending PCT Patent Application No. PCT/CA2015/050739 to Ryan Church, filed on even date, entitled FLUID-REDIRECTING STRUCTURE, the contents of which are incorporated herein by reference.

(34) Furthermore, the above-described configurations to the rotor blade of a horizontal-axis wind turbine can also be applied to vertical-axis wind turbines, and both of any scale. Such improvements may apply equally well to any arbitrary airfoil, not depending on the aerodynamic design thereof, mutatis mutandis, with such mutations as being relevant, including but not limited to, high altitude wind power (HAWP) devices, kite wind turbines, energy kites, urban wind turbines, airplane wings, gliders, drones and other things. The invention or inventions described herein may be applied to wind turbines having fewer or more blades than described by way of example in order to increase the operational efficiency and noise reduction capabilities of a wind turbine, to decrease vibration, loads, maintenance costs and mechanical wear, and to increase the scalability and marketability of such wind turbines.

(35) As for urban wind turbines, such devices could all benefit from having both leading and trailing edge projections on their airfoils. For screw type devices, (http://inhabitat.com/eddy-gt-wind-turbine-is-sleek-silent-and-designed-for-the-city/) they would be placed on both leading and trailing edges.

(36) Some embodiments may have been described with reference to method type claims whereas other embodiments may have been described with reference to apparatus type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters, in particular between features of the method type claims and features of the apparatus type claims is considered as to be disclosed with this document.

(37) The aspects defined above and further aspects are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment.

(38) Other aspects may become apparent to the skilled reader upon review of the following.

(39) Although embodiments have been described with reference to the drawings, those of skill in the art will appreciate that variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims.

(40) The above-described rotor blade configurations for a horizontal-axis wind turbine can also be applied to one or more rotor blades usable for vertical-axis wind turbines, and both of any scale, or to one or more rotor blades usable in hydroelectric dam turbines, gas turbines, tidal turbines or airborne wind energy turbines or in other kinds of turbines dealing with fluid flow whether of gas or of liquid.

(41) The above-described rotor blade configurations may alternatively be employed in aircraft such as commercial airliners, military jet aircraft, helicopter blades, helicopter wings, civilian airplanes, drones, and other similar aircraft. The invention or inventions described herein may be applied to wind turbines having fewer or more blades than described by way of example in order to increase the operational efficiency of a wind turbine, to decrease maintenance costs, and to increase the scalability and marketability of such wind turbines.

(42) It is observed that commercial airliners, civilian airplanes, drones, helicopter wings would have a winglet of similar size ratio to those of modern commercial airliners, with an architecture that bends back beyond the line of the trailing edge.

(43) A structure as described herein may contain miniature projections that reduce impact forces of rain and snow, thus limiting erosion and blade failure.

(44) Furthermore, a structure such as that described herein may be provided with a surface treatment such as a series of dimples and/or a series of hexagonal patterns and/or a series of troughs or grooves, all of which may either be sunk into the surface or raised above the surface of the winglet, such as is described in the above-mentioned co-pending PCT Application to Ryan Church entitled STRUCTURE WITH RIGID WINGLET ADAPTED TO TRAVERSE A FLUID ENVIRONMENT.

(45) Structures such as those described herein may apply equally well, mutatis mutandis, with such mutations as being relevant, including but not limited to, commercial airliners, military jet aircraft, helicopter blades, helicopter wings, civilian airplanes, spacecraft, drones, and other things.

(46) Furthermore, the structures disclosed herein are usable in other fluid environments besides ambient air, such as water environments, oil environments and so forth.

(47) The structure adapted to traverse a fluid environment may be applied to a vertical-axis wind turbine.

(48) The structure adapted to traverse a fluid environment may be applied to a hydroelectric dam turbine.

(49) The structure adapted to traverse a fluid environment may be applied to a gas turbines.

(50) The structure adapted to traverse a fluid environment may be applied to a tidal turbines.

(51) The structure adapted to traverse a fluid environment may be applied to an airborne airborne wind energy turbine.

(52) The structure adapted to traverse a fluid environment may be applied to a commercial airliner.

(53) The structure adapted to traverse a fluid environment may be applied to a military jet aircraft and to a spacecraft.

(54) The structure adapted to traverse a fluid environment may be applied to a helicopter blade.

(55) The structure adapted to traverse a fluid environment may be applied to helicopter wings.

(56) The structure adapted to traverse a fluid environment may be applied to wings of civilian airplanes.

(57) The structure adapted to traverse a fluid environment may be applied to wings of a drone.

(58) Structure described herein may be formed by various methods, including using 3D printing for the projections, or manufacturing the projections is with pre-impregnated technology, pultrusion, automated fibre placement (AFP), and/or injection moulding.

(59) It should be noted that the term comprising does not exclude other elements or steps and the use of articles a or an does not exclude a plurality. Also, elements described in association with different embodiments may be combined. It should be noted that reference signs in the claims should not be construed as limiting the scope of the claims.