Method for applying hydrodynamically functional films to complex wings
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- LUFTHANSA TECHNIK AG
- Filing Date
- 2024-03-14
- Publication Date
- 2026-08-06
Smart Images
Figure 2026526201000001_ABST
Abstract
Description
Technical Field
[0004] , ,
[0001] The present invention relates to a method for providing a hydrodynamically effective film having a microstructured surface to an object through which the surrounding flow passes in a complex form, particularly to a civil aircraft. Furthermore, the present invention relates to an object through which the surrounding flow passes in a complex form, to which a hydrodynamically effective film is applied, and to a film designed to be applied to an object through which the surrounding flow passes in a complex form.
Background Art
[0002] Hydrodynamically, particularly aerodynamically functional films, are known from the prior art in various forms and fields of application and generally serve to reduce the wall shear stress on the surface of an object through which the surrounding flow passes. For this purpose, a hydrodynamically functional film usually has a microstructured surface having one or more preferred directions. Here, the preferred direction is the preferred direction through which the flow passes (i.e., the local flow direction on the surface), in which the reduction of the wall shear stress is particularly large or even maximum.
[0003] A common microstructure is the so-called riblet structure, which has very small ribs extending substantially in the preferred direction. The ribs or riblets may be arranged parallel to each other, extend parallel over a long distance, and have the same geometric shape with respect to distance, height, and angle. However, the ribs may have a periodically changing pattern (so-called 3D riblets). For example, the riblet structure can be seen on the outer surface of an aircraft, but can also be seen on the rotor blades of a wind turbine, the hull of a ship, or the outer surface of a high-speed train.
[0004] In order to be able to maximally reduce the wall shear stress by the riblet structure, the film must be aligned as accurately as possible in its preferred direction or aligned with a slight deviation with respect to the local flow direction (i.e., the direction in which the flow on the surface of that region of the film is expected to mainly pass).
[0005] On surfaces through which a flow passes, where the flow profile is not very complex, is usually nearly uniform, and the direction of the flow, and therefore the preferred direction, is substantially predictable, riblet structures can be created very easily. Examples of such surfaces are the skin of a high-speed train, where the flow direction is proportional to the direction of travel, or the upper surface of an aircraft wing or wind turbine blade, where the flow direction is essentially in the direction of the profile.
[0006] However, even on the surface of an object with a more complex flow profile, it is generally desirable to provide an aerodynamically functional film that reduces wall shear stress in order to reduce the flow resistance of the object as much as possible as the flow passing around it. In the case of civil aircraft of known configurations, such areas are located, for example, in at least a portion of the outer skin of the aircraft's fuselage.
[0007] The complex flow profile in the corresponding region can be easily determined, for example, using appropriate simulations. Then, based on this, in principle, the preferred arrangement of the riblet film in this region can also be determined. Generally, however, a number of smaller regions are identified, and in each of these, a riblet film with a predetermined alignment with respect to its preferred direction is arranged. This results in a pattern of different riblet films or riblet film regions, each with a different alignment in the preferred direction.
[0008] Even if theoretically possible and generally advantageous in reducing wall shear stress, the application of hydrodynamically functional films, which have a preferred direction and must be aligned accordingly, has been shown to be extremely complex and time-consuming in regions where the surrounding flow is more complex. The hydrodynamically functional film must be individually cut for each region at its specific predetermined alignment and precisely applied in the preferred direction according to that predetermined alignment.
[0009] Due to the considerable effort required to apply hydrodynamic functional films to areas with complex surrounding flows, significant downtime occurs in applications such as aircraft. Furthermore, the application requires substantial human effort, particularly to determine and maintain the precise alignment and positioning of the film. [Overview of the project] [Problems that the invention aims to solve]
[0010] The object of the present invention is to provide a method, an object, and a film that do not suffer from or only suffer from the drawbacks of the prior art, an object through which a flow passes in a complex manner. [Means for solving the problem]
[0011] This objective is achieved by the subject matter of the independent claim. Favorable developments are the subject matter of the dependent claim.
[0012] Therefore, the present invention provides a method for providing a hydrodynamically effective film having a microstructured surface to an object, particularly a civil aircraft, which has at least one identifiable alignment line and through which a flow passes in a complex manner, The steps include determining an optimized surface structure for a continuous surface region of an object through which a flow passes in a complex shape, which is directly adjacent to at least one alignment line and through which the flow passes in a complex shape, The steps of manufacturing a hydrodynamically effective film having at least one edge having a microstructured surface corresponding to a determined surface structure, which is provided to align with at least one alignment line when correctly positioned, The steps include: applying the manufactured film to an object through which a flow passes in a complex pattern, aligning the edges provided for this purpose with alignment lines provided for this purpose, and applying the film in such a way that it covers a continuous surface area; Regarding methods including
[0013] Furthermore, the present invention relates to an object having at least one identifiable alignment line, around which a flow passes in a complex manner, wherein a hydrodynamically functional film is provided on at least one surface region adjacent to the alignment line by the method according to the present invention.
[0014] Furthermore, the present invention relates to a hydrodynamically functional film manufactured according to steps (a) and (b) of the method according to the present invention.
[0015] First, some terms used in relation to the present invention will be explained.
[0016] An "object through which a flow passes in a complex form" is an object whose shape, at least in a portion of its surface, creates a complex flow profile along its surface, even when the object is located in a parallel flow.
[0017] A "complex flow profile" is a flow profile that follows a surface area where a parallel flow profile cannot be reasonably approximated.
[0018] A "surface region through which a flow passes in a complex form" is a clearly defined, arbitrarily designed portion of the surface of an object through which a flow passes in a complex form, and which is a portion where a complex flow profile exists regardless, even in the case of parallel flows.
[0019] An "identifiable alignment line" may be a structural feature on the surface of an object, such as an edge or gap on the object's surface. However, an alignment line can be identifiable if just two distinct points are clearly identifiable on the alignment line, in which case it can be marked on the object, for example, using a line made of thread or an elongated adhesive piece. The corresponding points on the alignment line may be formed by structural features on the surface of the object, such as holes, screws, rivets, frames, or frame members, or they may be generated by measurements starting from such structural features.
[0020] According to the present invention, unlike the prior art, instead of identifying partial surfaces on a given surface region covered by a complex flow where film portions are each positioned at a predetermined alignment, the present invention identifies at least one alignment line adjacent to the surface region in question, manufactures a film aligned to this at least one alignment line, and the surface of such a film is microstructured in such a way that, when correctly positioned along the at least one alignment line, the film directly conforms to the complex flow profile within the region.
[0021] Since the film is configured to align with at least one alignment line according to the present invention, the final application of the film is significantly simplified and can be performed quickly: the film is simply applied to at least one alignment line in a manner aligned with the surface of an object through which a flow passes, and the surface structure configured to align with the complex flow on the surface region covered by the film is directly provided by the microstructured surface of the film. The complex alignment of individual subfilms, as known from the prior art, is no longer required.
[0022] In order to enable the manufacture and application of the corresponding film, the determination of an optimized surface structure for a generally predetermined surface area should be determined in the first step of the method according to the present invention. The surface area is a portion surface of an object around which a flow passes in a complex form, and the surface area is distinguished by being directly adjacent to at least one alignment line, or selected in correspondence to be directly adjacent to at least one alignment line.
[0023] For the practical determination of an optimized surface structure in a surface region, it is usually, but at least preferable, that the complex flow on the surface region is first determined, and then the appropriate surface structure can be determined based on that. The complex flow around an object in the surface region can be determined, for example, by CFD simulation. Determining the optimized surface structure based on this corresponds in principle to methods known from the prior art. Artificial intelligence can also be used to determine the optimized surface structure without relying on the intermediate step of determining the flow on the surface region.
[0024] The optimized surface structure may include, for example, two or more regions, each having riblets, but the riblets are oriented differently in at least two of the regions. Alternatively, or in addition, the geometric shapes of the riblets may differ in at least two of the regions. The geometric shapes of the riblets include, for example, the height of individual riblets and the distance between two adjacent riblets. Also, at least one of the regions may have a periodically changing pattern of riblets, i.e., 3D riblets. If two regions have 3D riblets, their periodically changing patterns may differ.
[0025] In the next step, a film is manufactured based on the optimized surface structure, and the surface of the film is microstructured in such a way that if the film is correctly aligned with one or more alignment lines by one or more edges and applied to the entire surface of an object through which the flow passes in a complex form in the surroundings, the microstructured surface of the film realizes the microstructuring within the surface area corresponding to the previously determined surface structure.
[0026] The film or its microstructuring may in principle be manufactured additively or subtractively. Thus, only the film as a whole or the microstructuring (for example, based on the film material) can be created by 3D printing, the application of a lacquer, in particular a UV-curing lacquer, which is appropriately embossed before curing or at least before complete curing, or by spraying. The subtractive process includes any machining method such as milling or grinding, in particular the laser ablation method. Of course, any combination of different additive and / or subtractive processes is also possible. In contrast, for example, the extrusion manufacturing method of a riblet film known from the prior art is generally not suitable because it can only manufacture a film with uniformly oriented riblets.
[0027] The film manufactured in this way is designed to fit a specific surface area of an object through which the flow passes in a complex form in the surroundings and can be applied to the corresponding surface area in the final step, particularly simply and quickly compared to the methods of the prior art.
[0028] For this purpose, the film must be aligned and fixed to the alignment line by at least one edge provided therefor. It is particularly preferable if the film has two non-parallel edges that are aligned with two corresponding non-parallel alignment lines. When the film is aligned with two non-parallel alignment lines simultaneously, its position is clearly determined, and as a result, it is guaranteed that the surface structure achieved by the film on an object through which the flow passes in a complex form in the surroundings corresponds to the previously determined optimized surface structure.
[0029] If a surface area to be covered by the film has components or elements that are intended to be accessible or not covered by the film after the film has been applied, or must be so, then appropriate notches or perforations for partial cutting and removal of the film portion at a later date may already be provided in the film during its manufacture. For example, if a window or flap is provided in the surface area in question, the film may already have notches for this purpose during manufacture, so that these notches are positioned directly over the surface area when the film is precisely placed on it. In particular, if the structural integrity of the film is reduced in a manner that makes application of the film difficult due to the notches or the like, perforations may be provided instead to allow for easy removal of a portion of the film after application. For example, perforations may be provided around the area of a window or flap so that the window or flap is covered by the film immediately after application, but is exposed again after the film has been removed along the perforations. In this case, it is preferable that the film be firmly attached only in areas where the film is intended to remain permanently on the surface of an object around which flow passes in a complex manner once applied. A notch may also be provided to prepare a two-dimensionally manufactured film for application to a three-dimensionally curved surface area or a surface area with an angle. For example, a horizontal triangular notch may be provided in the film, and the legs of the triangle will close and, in principle, touch each other when actually applied to a complexly curved film.
[0030] When the surface area to be covered with the film is large, it may be difficult to apply the entire film as a single unit. In this case, the film can be divided into tiles, with at least one tile having an edge that aligns to at least one alignment line. If two non-parallel alignment lines are provided, preferably one of the tiles is designed to align to both alignment lines and has corresponding edges. Once at least one tile is aligned to at least one alignment line and correctly applied, the remaining tiles can be aligned to the already placed tiles. The tiles may be shaped so that two adjacent tiles interlock at least partially. This greatly simplifies the correct placement of the remaining tiles.
[0031] For larger films or tiles, they may be rolled after manufacturing in such a way that edges provided for alignment lines or alignment with another tile are exposed. The film can then be aligned in a substantially rolled state, and once aligned, it can be applied by spreading it out over the entire surface to be covered by the film. The application of film, including spreading out a rolled film, is essentially known from the prior art.
[0032] The film is preferably self-adhesive. The manufacture of suitable adhesives and adhesive layers on films is known from the prior art. If the film includes areas separated by perforations and intended to be removed again after application to an object around which a flow passes in a complex manner, it is preferable that the film does not provide self-adhesion in these areas.
[0033] With regard to an object according to the present invention, which is preferably an aircraft or civilian aircraft, and a hydrodynamic film according to the present invention, a flow passes around it in a complex manner, the above embodiments are referenced.
[0034] Herein, the present invention will be described by example, based on advantageous embodiments with reference to the accompanying drawings. [Brief explanation of the drawing]
[0035] [Figure 1] This shows a schematic external view of a portion of an object through which a flow passes in a complex pattern. [Figure 2] Figure 1 shows a schematic diagram of a film manufactured according to the present invention for an object through which a flow passes in a complex shape. [Figure 3] Figure 2 shows a film in an object from Figure 1, where a flow passes through the surrounding area in a complex pattern. [Figure 4] Figure 2 shows a schematic diagram of a variant embodiment that serves as an alternative to the film. [Modes for carrying out the invention]
[0036] Figure 1 schematically shows a portion of object 1, specifically a portion of the rear of a civilian aircraft, through which a complex flow pattern passes.
[0037] On an object 1 through which a flow passes in a complex pattern, there are easily visible longitudinal grooves 2 that can be used as alignment lines 11. Furthermore, there is a region of rivets 3, from which further alignment lines 11 can be derived, i.e., lines passing through two predetermined rivets in the region of rivets 3. The further alignment lines 11, shown as dashed lines in Figure 1, can be made clearly visible temporarily, if necessary, for example, by a thread or appropriate laser projection. The two alignment lines 11 are perpendicular to each other, as seen in Figure 1.
[0038] A surface region 10, intended to provide a hydrodynamically effective film 20 (see Figure 2), is defined adjacent to two alignment lines 11. The surface region 10 extends to a tapered region 5 of object 1, which has a window opening 4 and around which the flow passes in a complex shape.
[0039] Starting from the situation shown in this figure, the optimized surface structure for the entire surface region 10 is first determined. For example, known tools such as CFD simulations of the flow through object 1, or at least the flow in the surface region 10, can be used for this purpose, along with the subsequent optimization of the surface structure for the surface region 10.
[0040] Next, based on the determined optimized surface structure, a film 20 as shown in Figure 2 is manufactured.
[0041] The film 20 is designed to cover the entire surface area 10 when applied to an object 1 through which a flow passes in a complex shape (see Figure 3). For easy and accurate application, the film 20 has two edges 21 provided to align with alignment lines 11: when the film 20 is applied in a manner aligned by the two edges 21 to the alignment lines 11 provided for this purpose, it is ensured that not only is the entire surface area 10 covered by the film, but a surface structure according to the determined optimized surface structure is also obtained.
[0042] In other words, the film 20 has a microstructured surface that is already adapted to a surface structure optimized for the surface region 10 during the manufacturing of the film 20. In the illustrated exemplary embodiment, the film 20 is manufactured by 3D printing onto a film material. However, any other additional and / or subtractive manufacturing processes are possible.
[0043] In the illustrated example, the microstructuring of the surface of the film 20 is designed as a riblet structure 2, and as can be clearly seen in Figure 2, multiple regions 22 with different alignments of riblets 23 are provided within the film 20, so that in the applied state (see Figure 3), a predetermined optimized surface structure can actually be generated within the surface region 10.
[0044] The perforations 24 are provided around the area corresponding to the window opening 4 (see Figure 1) in the applied state, so that the inner portion 24' can be easily removed at a later time, i.e., after application, to open the window opening 4. Unlike the rest of the area, the film 20 is not self-adhesive inside the perforations 24.
[0045] The film 20 has notches 25 in the portion that coincides with the tapered region 5 of object 1, around which the flow passes in a complex shape when applied. These notches allow, or at least simplify, application to the entire surface of the film 20. The notches 25 are triangular, and when applied, the two legs 26 of the triangular notches 25 are brought close to each other and directly overlap each other (see Figure 3).
[0046] Next, the manufactured film 20, as shown in Figure 2, is applied to an object through which a flow passes in a complex shape. In this case, the film 20 is aligned by its edge 21 to the corresponding alignment line 10 on the object 1 through which the flow passes in a complex shape, and the triangular cutout 25 is closed upon application, as shown and illustrated in Figure 3. As already mentioned, since the film 20 is self-adhesive, it can be applied to the object 1 through which a flow passes in a complex shape using known methods.
[0047] To facilitate application, the film 20 may be rolled up. Starting from Figure 2, the film 20 is rolled from bottom to top, so that when the film 20 is unrolled to at least a certain extent, the edge 21 is exposed and can be used for alignment with the alignment line 11. Appropriate methods for applying rolled self-adhesive films are known from the prior art and are usable.
[0048] Instead of rolling up the film, the film can be divided into individual tiles 27, as shown in Figure 4, with the aim of having easily manageable tile sizes rather than having the riblet alignment be performed roughly along different regions. It is essential that each tile 27' further has two edges 21 provided for alignment. The tiles 27' can then be applied to an object 21 in which the flow is in a complex shape, aligned to the corresponding positioning lines 11. Once the first tile 27' is correctly positioned, the remaining tiles 27 can be applied in an orientation toward this tile or the already applied tile 27.
Claims
1. A method for providing a hydrodynamically effective film (20) having a microstructured surface to an object (1), particularly a civil aircraft, which has at least one identifiable alignment line (11) and through which a flow passes in a complex manner, - A step of determining an optimized surface structure for a continuous surface region (10) of an object (1) through which a flow passes in a complex manner, which is directly adjacent to at least one alignment line (11) and through which a flow passes in a complex manner. - A step of manufacturing a hydrodynamically effective film (20) having at least one edge (21) that is provided to align with at least one alignment line (11) when correctly positioned and has a microstructured surface corresponding to the determined surface structure, - The steps of applying the manufactured film (20) to an object (1) through which a flow passes in a complex manner, such that the edges (21) provided for alignment are aligned to the alignment lines (11) provided for this purpose, and the film covers the continuous surface area (10). A method that includes this.
2. The complex flow around the object (1) in the surface region (10) is preferably determined by CFD simulation, and the optimized surface structure for this surface region (10) is determined based on the flow around the object. The method according to claim 1, characterized in that
3. The optimized surface structure has at least two regions (22) having a riblet structure, and at least the alignment and / or geometric factors of the riblets (23) in at least two of the regions (22) are different from each other. The method according to claim 1 or 2, characterized in that
4. The hydrodynamically effective film (20) is manufactured by one or more additional processes and / or one or more subtractive processes. The method according to any one of claims 1 to 3, characterized in that
5. The hydrodynamically effective film (20) has two non-parallel edges (21) that are aligned to two corresponding non-parallel alignment lines (11). The method according to any one of claims 1 to 4, characterized in that
6. During the manufacturing of the film (20), notches (25) and / or perforations (24) are provided for partial cutting and removal of portions of the film. The method according to any one of claims 1 to 5, characterized in that
7. The film (20) is divided into tiles, and at least one tile has an edge that is aligned with the at least one alignment line. The method according to any one of claims 1 to 6, characterized in that
8. The film (2) is rolled up after manufacturing in such a manner that it exposes the edge (21) which is provided to be aligned to an alignment line (11) or another tile (27). The method according to any one of claims 1 to 7, characterized in that
9. The aforementioned film (20) is self-adhesive. The method according to any one of claims 1 to 8, characterized in that
10. An object (1) having at least one identifiable alignment line (11) around which a flow passes in a complex shape, An object (1) characterized in that a hydrodynamically functional film (20) is provided on at least one surface region (10) adjacent to the alignment line (11) by the method described in any one of claims 1 to 9.
11. The object (1) through which the flow passes in a complex manner is an aircraft, preferably a civilian aircraft. An object as described in claim 11, characterized in that a flow passes around it in a complex manner.
12. A product manufactured according to steps (a) and (b) of the method described in claim 1, A hydrodynamically functional film (20) characterized by the above.
13. Manufactured in accordance with any one of claims 2 to 9, A hydrodynamically functional film (20) according to claim 12, characterized in that...