A bionic shark scale drag reduction structure and a preparation method thereof

Abstract

The application discloses a bionic shark shield scale drag reduction structure and a preparation method thereof, and the method comprises the following steps: building a femtosecond laser processing light path, shaping a femtosecond laser beam by using a spatial light modulator, realizing large-area processing of a tilted and curved microstructure on a metal material surface, and obtaining a microstructure with a certain curvature and depth. The bionic shield scale drag reduction structure not only realizes the groove drag reduction between shield scale structures, but also simulates the attack angle drag reduction of the shield scale structure, and can further improve the surface drag reduction performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of bionic drag reduction technology, and relates to a bionic shark scale drag reduction structure and a preparation method. BACKGROUND

[0002] Reducing the frictional resistance of the surface of an aircraft, a ship and the like is an important breakthrough for energy saving, consumption reduction, flight time and voyage distance increase, and has been listed by the United States NASA as one of the difficulties in breaking through the bottleneck of aviation and navigation technology in the future. It has been found that a shark's body surface is covered with a unique scale structure, which can optimize the fluid structure of the fluid boundary layer on the surface of the shark's body, inhibit and delay the occurrence of turbulence, thereby effectively reducing the water resistance and obtaining an extremely high swimming speed. The discovery of the shark skin scale drag reduction microstructure provides inspiration for the bionic preparation of microstructure to reduce the frictional resistance of the surface of a material. Most of the current researches simplify the shark scale structure into a groove structure, and prepare drag reduction grooves with triangular, rectangular, semicircular, trapezoidal and other shapes on the surface of a material to reduce the drag of the material surface. Patent CN105644770B proposes a bionic shark skin drag reduction wing, which processes a groove type rib structure on the surface of the wing skin to reduce the drag of the aircraft. However, the simple groove structure cannot completely reflect the real drag reduction principle of the shark skin scale structure. Therefore, obtaining a bionic shark skin with a more realistic bionic scale structure is an effective means to further improve the surface drag reduction performance. At present, various methods for directly copying the simulation scale structure, such as micro-hot embossing and micro-plastic casting, all use polymer materials, and the copying of the scale bionic surface structure from non-metallic materials to metallic materials has not been achieved. Therefore, how to realistically bionically prepare a shark scale structure on the surface of a metallic material and achieve the preparation of a scale drag reduction structure on the surface of a metallic material has become a difficult problem to be solved. SUMMARY

[0003] The present application aims to overcome the shortcomings of the prior art, and provides a bionic shark scale drag reduction structure and a preparation method, so as to solve the problems of the bionic scale structure in the prior art, such as difficulty in realistically imitating the shark skin and the scale structure not being a metallic material.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0005] A bionic shark scale drag reduction structure, comprising a drag reduction material base body, wherein the drag reduction material base body is arrayed with drag reduction microstructures along the length direction and the width direction;

[0006] The front side of the drag reduction microstructure is a back flow surface, and the back side is a flow surface, the flow surface is opposite to the fluid flow direction, and the back flow surface and the flow surface are both arc surfaces; the upper ends of the back flow surface and the flow surface are integrally connected, the bottom of the back flow surface is integrally connected with the drag reduction material base body, and the bottom of the flow surface is integrally connected with the drag reduction material base body;

[0007] The arc line of the fluid flow direction section of the incident flow surface is an incident flow line, and the arc line of the fluid flow direction section of the back flow surface is a back flow line; on the same fluid flow direction section, the curvature of the incident flow line is greater than the curvature of the back flow line.

[0008] The drag reduction material base and the drag reduction microstructure are both metal materials.

[0009] Further improvements of the present application are as follows:

[0010] Preferably, the fluid grooves between adjacent drag reduction microstructures are parallel to the fluid flow direction.

[0011] Preferably, the width of the fluid groove is 100-150 μm, and the height of the fluid groove is 400-500 μm.

[0012] Preferably, the tangent plane of the incident flow surface at the contact with the drag reduction material base is perpendicular to the surface of the drag reduction material base.

[0013] Preferably, the tangent plane of the back flow surface at the contact with the drag reduction material base is perpendicular to the surface of the drag reduction material base.

[0014] Preferably, the height of the drag reduction microstructure is 400-500 μm, the thickness is 150-200 μm, and the width is 200-250 μm.

[0015] Preferably, the distance between adjacent drag reduction microstructures in the fluid flow direction is 100-150 μm.

[0016] A preparation method of the above-mentioned bionic shark scale drag reduction structure, which comprises the following steps: fixing a metal sample on a moving stage; and processing the metal sample by a femtosecond laser to obtain a drag reduction material base and drag reduction microstructures arranged on the drag reduction material base.

[0017] Preferably, the preparation process comprises the following steps:

[0018] Step 1: setting up a femtosecond laser light path, and fixing a metal sample on a moving stage; the femtosecond laser light path comprises a femtosecond laser, and the laser emitted by the femtosecond laser is sent to a scanning galvanometer through a spatial light modulator;

[0019] Step 2: moving the laser spot to process the metal sample by controlling the scanning galvanometer with a computer, so as to obtain a drag reduction material base and drag reduction microstructures arranged on the drag reduction material base.

[0020] Preferably, a mirror is arranged between the femtosecond laser and the spatial light modulator; and a mirror is arranged between the spatial light modulator and the scanning galvanometer.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] The application provides a bionic shark denticulate drag reduction structure which is more close to the denticulate structure of a shark in shape and size, realizes preparation of a bionic denticulate drag reduction structure on a metal material surface, and realizes not only the groove drag reduction between the denticulate structures but also the angle of attack drag reduction of the denticulate structures, so that the surface drag reduction performance can be further improved.

[0023] The application provides a preparation method of a bionic shark denticulate drag reduction structure. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 FIG. 1 is a schematic diagram of a bionic shark denticulate drag reduction structure.

[0025] Figure 2 FIG. 2 is a schematic diagram of a side surface of the bionic shark denticulate drag reduction structure.

[0026] Figure 3 FIG. 3 is a schematic diagram of femtosecond laser processing.

[0027] In the figure, 1 is a drag reduction microstructure, 2 is a drag reduction material matrix, 3 is a fluid groove, 4 is an incident flow surface, 5 is a backflow surface, 6 is a femtosecond laser, 7 is a mirror, 8 is a spatial light modulator, 9 is a scanning galvanometer, 10 is a metal sample, 11 is a sample stage, 12 is an incident flow line, and 13 is a backflow line. DETAILED DESCRIPTION

[0028] The application will be further described in detail below with reference to the accompanying drawings:

[0029] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] One embodiment of the present invention discloses a drag-reducing microstructure 1 based on a biomimetic shark dermal scutes structure, such as... Figure 1 As shown, drag-reducing microstructures 1 are disposed on the surface of drag-reducing material substrate 2, forming a large-area array on the upper surface of drag-reducing material substrate 2. Adjacent drag-reducing microstructures 1 in the direction perpendicular to the fluid flow direction form fluid channels 3, the length of which is parallel to the fluid flow direction. Let the direction of fluid flow be defined as forward, the opposite direction as backward, the left side of the fluid flow direction as left, and the other side as right. Subsequent content will be based on this direction and will not be elaborated further.

[0031] See Figure 1 and Figure 2 The drag-reducing microstructure 1 has a thumb-like shape and a biomimetic shield-scale structure at the top of the structure. Based on the flow direction of the fluid on the surface of the drag-reducing microstructure 1, it is divided into a frontal surface 4 and a backal surface 5. Both the frontal surface 4 and the backal surface are arc surfaces with the same curvature direction. The upper ends of the frontal surface 4 and the backal surface 5 are integrally connected, and the bottom ends of both the frontal surface 4 and the backal surface 5 are connected to the surface of the drag-reducing material matrix 2. The frontal surface 4 and the fluid flow direction are opposite to each other. The arc of the frontal surface 4 in the fluid flow direction section is designated as the frontal line 12, and the arc of the backal surface 5 in the fluid flow direction section is designated as the backal line 13. The curvature of the frontal line 12 is greater than that of the backal line 13. The curvature directions of the frontal line 12 and the backal line 13 are the same, and the length of the frontal line 12 is greater than that of the backal line 13, so that the cross-section formed by the frontal surface 4 and the backal surface 5 of the drag-reducing microstructure resembles a sail.

[0032] Preferably, the height of the drag reduction microstructure 1 is between 400-500 microns, the front and back thickness is between 150-200 microns, the front and back distance of the drag reduction microstructure is between 100-150 microns, and the left and right distance of the drag reduction microstructure is between 200-250 microns.

[0033] Preferably, at the contact between the flow surface 4 and the drag reduction material base 2, the tangent plane of the flow surface 4 is perpendicular to the surface of the drag reduction material base 2; at the contact between the backflow surface 5 and the drag reduction material base 2, the tangent plane of the backflow surface 5 is perpendicular to the surface of the drag reduction material base 2.

[0034] The fluid channel 3 is in the same direction as the fluid flow, and a part of the fluid can also flow forward along the fluid channel 3. The width of the fluid channel 3 is between 100-150 microns, and the depth is consistent with the height of the drag reduction microstructure 1 formed, which is between 400-500 microns.

[0035] One of the embodiments of the present application discloses a device for preparing a bionic shark shield scale structure, as shown in Figure 3 The device comprises a femtosecond laser 6, two mirrors 7 are arranged on the light path emitted by the femtosecond laser 6, the light path is input into a spatial light modulator 8 through the first mirror 7, the light path output from the spatial light modulator 8 is input into a scanning galvanometer 9 through the second mirror 7, the scanning galvanometer 9 is arranged on a substrate through a supporting column, and a stage 11 is also arranged on the substrate, the stage 11 is used for placing a metal sample 10, and the metal sample 10 is below the lens of the scanning galvanometer 9.

[0036] One of the embodiments of the present application discloses a preparation method of a bionic shark shield scale drag reduction microstructure, which is a method for preparing a bionic shark shield scale structure based on spatial light modulation of femtosecond laser, and the specific steps are as follows:

[0037] 1) The surface of the metal sample 10 is ultrasonically cleaned with acetone and anhydrous alcohol respectively, and the clean sample surface is obtained by blowing cold air;

[0038] 2) Build a femtosecond laser processing light path, which comprises a femtosecond laser 6, the output light of the femtosecond laser 6 enters a spatial light modulator 8 after passing through a mirror 7, and the light after spatial shaping enters a scanning galvanometer 9 and irradiates on a stage 11, the femtosecond laser 6, the spatial light modulator 8 and the scanning galvanometer 9 are connected with a computer;

[0039] 3) Fix the metal sample 10 on the moving stage 11 processing station;

[0040] 4)Using computer control scanning galvanometer 9 to realize laser spot moving processing bionic shark scale drag reduction microstructure. Different laser power, lens size, laser parameters are adjusted in real time according to the target shape to be processed during laser processing.

[0041] The existing micro-nano structure processed by femtosecond laser can process different shapes of micro-nano structure by changing the processing parameters, such as power size, laser spot size, etc. However, this curved structure cannot be processed by normal femtosecond processing. The spatial light modulator 8 is added in the femtosecond laser light path, the distribution of light intensity is changed, and the processing of curved structure is realized by adjusting the spatial light modulator.

[0042] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A drag-reducing structure inspired by shark dermal denticles, characterized in that, It includes a drag-reducing material matrix (2), wherein drag-reducing microstructures (1) are arrayed along both the length and width directions of the drag-reducing material matrix (2); The front side of the drag-reducing microstructure (1) is a backflow surface (5), and the rear side is a frontflow surface (4). The frontflow surface (4) is opposite to the direction of fluid flow. Both the backflow surface (5) and the frontflow surface (4) are arc surfaces with the same bending direction. The upper ends of the backflow surface (5) and the frontflow surface (4) are integrally connected. The bottom of the backflow surface (5) is integrally connected to the drag-reducing material matrix (2), and the bottom of the frontflow surface (4) is integrally connected to the drag-reducing material matrix (2). The arc of the frontal surface (4) in the direction of fluid flow is the frontal line, and the arc of the backal surface (5) in the direction of fluid flow is the backal line; on the same cross section in the direction of fluid flow, the arc of the frontal line is greater than the arc of the backal line. The drag-reducing material matrix (2) and the drag-reducing microstructure (1) are both made of metal. At the contact point between the frontal surface (4) and the drag-reducing material matrix (2), the cross-section of the frontal surface (4) is perpendicular to the surface of the drag-reducing material matrix (2); The adjacent drag-reducing microstructures (1) are connected by a fluid channel (3), and the length direction of the fluid channel (3) is parallel to the fluid flow direction. The drag-reducing structure inspired by shark fins can be applied to aircraft or ships. The method for preparing the drag-reducing structure is as follows: Step 1: Construct a femtosecond laser optical path and fix the metal sample (10) on the moving stage (11); the femtosecond laser optical path includes a femtosecond laser (6), and the laser emitted by the femtosecond laser (6) is sent to the scanning galvanometer (9) through the spatial light modulator (8); Step 2: Using computer-controlled scanning galvanometer (9), the laser spot is moved to process the metal sample (10) to obtain the drag-reducing material matrix (2) and the drag-reducing microstructure set on the drag-reducing material matrix (2); The spatial light modulator (8) changes the distribution of light intensity to realize the processing of curved structures; The height of the drag-reducing microstructure (1) is between 400 and 500 micrometers, the front and rear thickness is between 150 and 200 micrometers, and the width is between 200 and 250 μm; The width of the fluid tank (3) is 100-150μm, and the height of the fluid tank (3) is 400-500μm; Along the direction of fluid flow, the distance between adjacent drag-reducing microstructures (1) is 100-150 μm.

2. The drag-reducing structure of a biomimetic shark dermal fin as described in claim 1, characterized in that, At the contact point between the backflow surface (5) and the drag-reducing material matrix (2), the cross-section of the backflow surface (5) is perpendicular to the surface of the drag-reducing material matrix (2).

3. A method for preparing a drag-reducing structure for biomimetic shark dermal scutes as described in claim 1, characterized in that, A drag-reducing material matrix (2) and drag-reducing microstructures on the drag-reducing material matrix (2) were prepared by processing a metal sample (10) with a femtosecond laser.

4. The method for preparing a drag-reducing structure for biomimetic shark dermal scutes according to claim 3, characterized in that, The preparation process includes the following steps: Step 1: Construct a femtosecond laser optical path and fix the metal sample (10) on the moving stage (11); the femtosecond laser optical path includes a femtosecond laser (6), and the laser emitted by the femtosecond laser (6) is sent to the scanning galvanometer (9) through the spatial light modulator (8); Step 2: Using computer-controlled scanning galvanometer (9), the laser spot is moved to process the metal sample (10) to obtain the drag-reducing material matrix (2) and the drag-reducing microstructure set on the drag-reducing material matrix (2).

5. The method for preparing a drag-reducing structure for biomimetic shark dermal scutes according to claim 4, characterized in that, A mirror (7) is provided between the femtosecond laser (6) and the spatial light modulator (8); a mirror (7) is provided between the spatial light modulator (8) and the scanning galvanometer (9).

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