A real-time vector velocity monitoring system based on fan blade guidance and FBG fiber optic sensing, its preparation method and usage method

Abstract

This invention provides a real-time vector velocity monitoring system, its fabrication method, and its application method based on fan-blade flow guidance and FBG fiber optic sensing. The system includes an integrated multi-channel vector sensing probe and a multi-channel fiber optic signal acquisition link. The sensing probe adopts a four-layer integrated vertically stacked structure comprising a flow guidance sensing layer, a mechanical transmission layer, a sensing decoupling layer, and a base layer. Flow field vector decomposition is achieved through a fan-blade flow guide, three-dimensional vector sensing is achieved through a four-point orthogonally symmetrical FBG array, and synchronous calculation of velocity magnitude and direction is achieved through a deep learning decoupling model. This invention solves the technical problems of insufficient multi-dimensional information acquisition, complex structure and low integration, and poor long-term stability of existing underwater velocity sensors, achieving high-precision, real-time synchronous monitoring of three-dimensional vector velocity.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, and more particularly to a real-time vector velocity monitoring system based on fan blade guidance and FBG fiber optic sensing, its preparation method, and its usage method. Background Technology

[0002] Underwater velocity measurement is a core technological requirement in fields such as marine environmental monitoring, safety assessment of hydraulic engineering projects, and underwater navigation. Accurate acquisition of three-dimensional vector velocity information (including velocity magnitude, horizontal direction angle, and vertical inclination angle) is crucial for analyzing complex flow fields. Traditional measurement methods mainly rely on single-point scalar or two-dimensional planar measurements, which are insufficient to meet the needs of analyzing velocity fields across the entire space. Furthermore, factors such as the corrosiveness of the underwater environment, biofouling, and pressure fluctuations pose severe challenges to the long-term stability and measurement accuracy of sensors, necessitating the development of novel sensing technologies to overcome existing limitations.

[0003] In existing technologies, mechanical current meters calculate flow velocity by rotor speed, but suffer from problems such as mechanical wear, insufficient sensitivity at low flow velocities, and inability to measure flow direction. Acoustic Doppler current profilers can achieve profile measurement, but they have near-boundary blind zones and are susceptible to interference from suspended matter. Electromagnetic current meters are significantly affected by changes in water conductivity. Regarding fiber optic sensing technology, sensors based on bending loss have low sensitivity and are difficult to quantify. Fabry-Perot interferometer schemes are mostly limited to single-axis measurements, while traditional FBG sensors typically employ cantilever beams or diaphragm structures, capable of sensing strain in only a single direction. These methods generally suffer from insufficient three-dimensional information decoupling capability, low system integration, and poor dynamic stability, making it difficult to achieve synchronous three-dimensional vector measurement in complex flow fields. Summary of the Invention

[0004] To address the technical problems of insufficient multi-dimensional information acquisition, complex structure and low integration, and poor long-term stability and reliability in existing technologies, this invention provides a real-time vector velocity monitoring system, its fabrication method, and its application method based on fan-blade flow guides and FBG fiber optic sensing. This invention primarily utilizes a fan-blade flow guide to achieve preliminary decomposition of the flow field vector and eddy current suppression, employs a four-point orthogonally symmetrical FBG array to achieve three-dimensional vector sensing, and utilizes a deep learning decoupling model to simultaneously calculate the magnitude and direction of the flow velocity. This results in improved measurement accuracy, enhanced system stability, and the achievement of synchronous three-dimensional vector monitoring.

[0005] The technical means employed in this invention are as follows:

[0006] A real-time vector velocity monitoring system based on fan blade guidance and FBG fiber optic sensing includes an integrated multi-channel vector sensing probe and a multi-channel fiber optic signal acquisition link, wherein: The integrated vector multi-channel sensing probe adopts a four-layer integrated vertical stacked structure. The layers are bonded together to form a continuous internal stress transmission path. From top to bottom, the layers are a flow-guiding sensing layer, a mechanical transmission layer, a sensing decoupling layer, and a base layer. The flow-guiding sensing layer is located at the top of the sensor and is a fan-shaped flow guide cover that directly withstands the impact of water flow, thereby achieving preliminary decomposition of the flow field vector and suppression of eddies. The mechanical transmission layer includes a central force-bearing column and a support rod, which serve as a rigid connecting rod between the flow-guiding sensing layer and the sensing decoupling layer, transmitting the resultant force of the water flow received by the flow-guiding sensing layer to the sensing decoupling layer. The sensing decoupling layer is the core sensing unit, comprising a highly elastic silicone substrate and four fiber Bragg gratings. The four fiber Bragg gratings are embedded in the silicone substrate in a four-point orthogonal symmetrical manner. The four fiber Bragg gratings are 90° apart on the horizontal projection plane, located at 0°, 90°, 180°, and 270° respectively. The centers of the grating regions of the four fiber Bragg gratings are located on the same horizontal plane in the longitudinal section and are equidistant from the radial distance of the central axis of the highly elastic silicone substrate. The center wavelengths of the four fiber Bragg gratings are uniformly distributed in the 1530nm to 1565nm band to ensure separation of the reflection spectrum without crosstalk. The base layer is used to fix and mount the entire sensor; The multi-channel fiber optic signal acquisition link includes a sensing probe, a 4×1 fiber coupler, and a fiber Bragg grating demodulator; the four fiber Bragg gratings of the sensing probe are connected to the fiber Bragg grating demodulator through the 4×1 fiber coupler.

[0007] Furthermore, the fan-shaped fairing is connected to the upper end of the central force-bearing column by adhesive bonding, and is composed of 10 identical blades evenly distributed around the circumference; each blade is a streamlined airfoil with a blade chord length of 15mm, a maximum blade thickness of 3mm, and a vertical blade length of 4mm; the 10 blades together form a fairing with an outer diameter of 25mm.

[0008] Furthermore, the central force-bearing column is a solid cylinder with a diameter of 8mm and a height of 10mm, and its lower end is provided with an adhesive surface; the central force-bearing column gathers the water flow impact force received by the fan-shaped guide shield into a resultant force and transmits it downward to the support rod.

[0009] Furthermore, the support rod is a cylindrical rod with a diameter of 3mm and a length of 15mm; the upper end of the support rod is fixed to the lower end of the central load-bearing column by high-strength epoxy structural adhesive; the lower end of the support rod is fixed to the center position of the upper surface of the high-elasticity silicone substrate by high-strength epoxy structural adhesive, the connection is to expand the contact area and use a flexible transition adhesive layer; the support rod transmits the force of water flow on the upper structure to the high-elasticity silicone substrate in the form of torque.

[0010] Furthermore, the silicone substrate is cylindrical with a diameter of 4 mm and a height of 25 mm. Inside the silicone substrate, along the circumferential direction, four rectangular microgrooves with a depth of 2 mm and a width of 1 mm are pre-fabricated on a circle 10 mm from the central axis. These four rectangular microgrooves are at 90° to each other on the horizontal projection plane, corresponding to 0°, 90°, 180°, and 270° orientations, respectively, for positioning four fiber Bragg gratings. All four fiber Bragg gratings are polyimide-coated fiber Bragg gratings with initial center wavelengths of 1540.0 nm, 1542.0 nm, 1544.0 nm, and 1546.0 nm, respectively.

[0011] Furthermore, silicone rubber is coated around the connection between the support rod and the high-elasticity silicone substrate; the sensor probe is provided with a streamlined shell, and polyurethane elastomer is injected inside the shell to form a uniform waterproof protective skin with a thickness of 2mm to 3mm, and the fan-shaped flow guide is partially exposed to the water flow; four optical fibers leading out from the side of the silicone substrate are integrated into an optical cable with a diameter of 3mm, and the optical cable is sealed with a through-type watertight joint between it and the sensor shell, and the joint is filled with waterproof gel.

[0012] The present invention also provides a method for preparing the above-mentioned real-time vector flow velocity monitoring system, comprising: S1. Processing and manufacturing silicone substrate molds, flow guide molds, and packaging shell molds; S2. Position and pre-tension four fiber Bragg gratings in the silicone matrix mold, pour and cure the silicone, and demold to obtain a highly elastic silicone matrix with built-in fiber Bragg gratings. S3. The fan blades, central force-bearing column and support rod are manufactured using 3D printing technology. The fan blades, central force-bearing column and support rod are then glued together to form a rigid whole, forming a flow guiding and mechanical transmission structure composed of fan blade-type flow guide, central force-bearing column and support rod. S4. Align the lower end of the support rod with the center of the upper surface of the silicone substrate and fix it in place. Align the lower end of the support rod with the center of the upper surface of the high elastic silicone substrate and fix it with high-strength epoxy structural adhesive. Expand the contact area at the connection and set a flexible transition adhesive layer to avoid stress concentration and damage to the silicone substrate. Fix the flow guiding and mechanical transmission structure composed of fan-shaped flow guide, central force column and support rod to the high elastic silicone substrate to form an integrated vector multi-channel sensing probe. S5. Place the integrated vector multi-channel sensing probe into the packaging shell mold, pour polyurethane to form a protective layer, install the armored optical cable and watertight connector, and complete the overall packaging and waterproofing treatment. S6. Connect the fiber optic grating demodulator to the computer, power on and test the spectral signal quality, and perform static calibration and water flow testing.

[0013] Furthermore, the specific operations of pre-tensioning in step S2 include: Apply pretension to each fiber Bragg grating and use UV-curing adhesive to temporarily fix both ends of the fiber Bragg grating to the positioning fixture to ensure that the grating section is straight; Four tensioned fiber Bragg gratings are placed into the corresponding rectangular microgrooves of the silicone substrate mold, ensuring that the center of the grating area is located in the central plane of the silicone substrate in the height direction. The silicone rubber, which is mixed and degassed in proportion, is poured into a mold to completely cover the fiber Bragg grating and rectangular microgroove. It is then cured in a 60°C oven for 2 hours to form an integrated structure of silicone matrix and fiber Bragg grating. After curing, the external fixing adhesive dots are cut off to release the pretension, so that the fiber Bragg grating remains taut under the constraint of the silicone.

[0014] The present invention also provides a method of using the above-mentioned real-time vector flow velocity monitoring system, comprising: Step 1: Mechanical transformation. The water flow impacts the fan-shaped guide shield. The impact force of the water flow is decomposed according to the direction of the water flow and transmitted to the central force column and support rod. The support rod transmits the force of the water flow to the silicone matrix in the form of torque, causing the silicone matrix to produce asymmetric deformation. Step 2, Optical Sensing: The deformation of the highly elastic silicone substrate causes the four fiber Bragg gratings embedded in the rectangular microgroove to generate center wavelength drifts corresponding to the strain states at their respective positions. The four fiber Bragg gratings generate first, second, third, and fourth center wavelength drifts, respectively. Since the four fiber Bragg gratings are orthogonally symmetrically arranged at 90° to each other on the horizontal projection plane, water flow in different directions generates four-channel wavelength drift combinations with different characteristics. Step 3: Signal Acquisition and Calculation. The reflected light from the four fiber Bragg gratings is combined through a 4×1 fiber coupler. The fiber grating demodulator collects the data of the first, second, third, and fourth center wavelength drifts in real time. After the data is transmitted to the computing unit, the trained deep learning decoupling model processes the combination of the four-channel wavelength drifts and outputs a three-dimensional flow velocity vector.

[0015] Furthermore, the deep learning decoupling model employs a neural network algorithm to calculate the flow velocity, horizontal direction angle, and vertical tilt angle through decoupling using four-channel wavelength drift data.

[0016] Compared with the prior art, the present invention has the following advantages: 1. The real-time vector velocity monitoring system based on fan-blade flow guide and FBG fiber optic sensing provided by the present invention achieves preliminary decomposition of flow field vector and eddy suppression through fan-blade flow guide, realizes three-dimensional vector sensing through four-point orthogonal symmetrical FBG array, and realizes synchronous calculation of flow velocity magnitude and direction through deep learning decoupling model, thus achieving high-precision, real-time synchronous monitoring of three-dimensional vector velocity.

[0017] 2. The present invention adopts a four-layer integrated vertical stacked structure. The layers are bonded together to form a continuous internal stress transmission path. The structure is compact and highly integrated, avoiding the complex wiring and signal interference problems of traditional multi-sensor arrays.

[0018] 3. This invention adopts all-fiber passive sensing technology, which is resistant to electromagnetic interference and corrosion. Optimized packaging ensures long-term underwater stability, with a dynamic response time of less than 50ms and a center wavelength drift of less than 0.01nm within 30 days.

[0019] 4. This invention adopts a streamlined airfoil blade structure, which effectively suppresses vortex-induced vibration, reduces the standard deviation of signal fluctuation to within ±0.4pm, achieves a flow velocity measurement linearity R²≥0.98, and has an average direction recognition error of less than 3° (horizontal) and less than 5° (vertical).

[0020] In summary, the technical solution of this invention solves the technical problems of insufficient multi-dimensional information acquisition, complex structure and low integration, and poor long-term stability and reliability of existing underwater current velocity sensors. Therefore, the technical solution of this invention overcomes the above-mentioned defects in the prior art. This invention can be widely applied in fields such as marine scientific research, environmental monitoring, hydraulic engineering, and underwater vehicle navigation. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the four-point wavelength division multiplexing (FBG) sensing system of the present invention.

[0023] Figure 2 This is a schematic diagram of the FBG vector sensor structure based on flexible silicone according to the present invention.

[0024] Figure 3 This is a schematic diagram of the sensor manufacturing process of the present invention. Detailed Implementation

[0025] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0029] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms 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, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0030] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0031] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0032] like Figure 1 , 2 As shown, this invention provides a real-time vector flow velocity monitoring system based on fan blade guidance and FBG fiber optic sensing, including an integrated vector multi-channel sensing probe and a multi-channel fiber optic signal acquisition link, wherein: The integrated vector multi-channel sensing probe adopts a four-layer integrated vertical stacked structure. The layers are bonded together to form a continuous internal stress transmission path. From top to bottom, the layers are a flow-guiding sensing layer, a mechanical transmission layer, a sensing decoupling layer, and a base layer. The flow-guiding sensing layer is located at the top of the sensor and is a fan-shaped flow guide cover that directly withstands the impact of water flow, thereby achieving preliminary decomposition of the flow field vector and suppression of eddies. The mechanical transmission layer includes a central force-bearing column and a support rod, which serve as a rigid connecting rod between the flow-guiding sensing layer and the sensing decoupling layer, transmitting the resultant force of the water flow received by the flow-guiding sensing layer to the sensing decoupling layer. The sensing decoupling layer is the core sensing unit, comprising a highly elastic silicone substrate and four fiber Bragg gratings (FBGs). The four FBGs are embedded in the silicone substrate in a four-point orthogonal symmetrical manner. The four FBGs are 90° apart on the horizontal projection plane, located at 0°, 90°, 180°, and 270° respectively. The centers of the grating regions of the four FBGs are located on the same horizontal plane in the longitudinal section and are equidistant from the radial distance of the central axis of the highly elastic silicone substrate. The center wavelengths of the four FBGs are uniformly distributed in the 1530nm to 1565nm band to ensure separation of the reflection spectrum without crosstalk. The base layer is used to fix and mount the entire sensor; The multi-channel fiber optic signal acquisition link includes a sensing probe, a 4×1 fiber coupler, and a fiber Bragg grating demodulator; the four fiber Bragg gratings of the sensing probe are connected to the fiber Bragg grating demodulator through the 4×1 fiber coupler.

[0033] In a preferred embodiment of the invention, the fan-shaped flow guide is connected to the upper end of the central support column by adhesive bonding and consists of 10 identical blades evenly distributed around its circumference. Each blade is a streamlined airfoil with a chord length (along the water flow direction) of 15 mm, a maximum blade thickness of 3 mm, and a vertical length of 4 mm. The 10 blades together form an outer diameter of... A 25mm flow deflector. In this embodiment, the single blade is a streamlined airfoil, which effectively guides the water flow and reduces periodic vibrations (vortex-induced vibration, VIV) caused by vortex shedding (Karman vortex street), thereby significantly reducing the noise level of the sensor output signal.

[0034] In a specific implementation, as a preferred embodiment of the present invention, the central force-bearing column is a solid cylinder with a diameter of 8mm and a height of 10mm, and its lower end is provided with an adhesive surface; the central force-bearing column gathers the water flow impact force received by the fan-shaped guide shield into a resultant force and transmits it downward to the support rod.

[0035] In a preferred embodiment of this invention, the support rod is a cylindrical rod with a diameter of 3mm and a length of 15mm. The upper end of the support rod is fixed to the lower end of the central load-bearing column via high-strength epoxy structural adhesive. The lower end of the support rod is fixed to the center of the upper surface of the high-elasticity silicone substrate via high-strength epoxy structural adhesive, with the connection point having an enlarged contact area and a flexible transition adhesive layer. The support rod transmits the force of the water flow acting on the upper structure to the high-elasticity silicone substrate in the form of torque. In this embodiment, the support rod acts as a "lever," transmitting the force of the water flow acting on the upper structure to the flexible silicone substrate in the form of torque. Its length... The length is a key balancing parameter between sensitivity and stability: too long a length increases torque (improves sensitivity) but lowers the structure's natural frequency (making it more prone to vibration); too short a length has the opposite effect. The optimized length of 15 mm achieved the best overall performance in the experiment.

[0036] In a preferred embodiment of the invention, the silicone substrate is cylindrical with a diameter of 4 mm and a height of 25 mm. Four rectangular microgrooves, each 2 mm deep and 1 mm wide, are pre-fabricated along the circumferential direction inside the silicone substrate, 10 mm from the central axis. These four microgrooves are at 90° angles to each other on the horizontal projection plane, corresponding to 0°, 90°, 180°, and 270° orientations, respectively, for positioning four fiber Bragg gratings. All four fiber Bragg gratings are polyimide-coated fiber Bragg gratings, with initial center wavelengths of... 1540.0nm 1542.0nm 1544.0nm 1546.0nm.

[0037] In a preferred embodiment of the invention, silicone rubber is coated around the connection between the support rod and the high-elasticity silicone substrate; the sensor probe is provided with a streamlined shell, and polyurethane elastomer is injected inside the shell to form a uniform waterproof protective skin with a thickness of 2mm to 3mm, with the fan-shaped flow guide partially exposed to the water flow; four optical fibers leading out from the side of the silicone substrate are integrated into an optical cable with a diameter of 3mm, and the optical cable is sealed with a through-type watertight joint between itself and the sensor shell, with the joint filled with waterproof gel.

[0038] like Figure 3 As shown, the present invention also provides a method for preparing the above-mentioned real-time vector flow velocity monitoring system, comprising: S1. Processing and manufacturing silicone substrate molds, flow guide molds, and packaging shell molds; S2. Position and pre-tension four fiber Bragg gratings in the silicone matrix mold, pour and cure the silicone, and demold to obtain a highly elastic silicone matrix with built-in fiber Bragg gratings. S3. The fan blades, central force-bearing column and support rod are manufactured using 3D printing technology. The fan blades, central force-bearing column and support rod are then glued together to form a rigid whole, forming a flow guiding and mechanical transmission structure composed of fan blade-type flow guide, central force-bearing column and support rod. S4. Align the lower end of the support rod with the center of the upper surface of the silicone substrate and fix it in place. Align the lower end of the support rod with the center of the upper surface of the high elastic silicone substrate and fix it with high-strength epoxy structural adhesive. Expand the contact area at the connection and set a flexible transition adhesive layer to avoid stress concentration and damage to the silicone substrate. Fix the flow guiding and mechanical transmission structure composed of fan-shaped flow guide, central force column and support rod to the high elastic silicone substrate to form an integrated vector multi-channel sensing probe. S5. Place the integrated vector multi-channel sensing probe into the packaging shell mold, pour polyurethane to form a protective layer, install the armored optical cable and watertight connector, and complete the overall packaging and waterproofing treatment. S6. Connect the fiber optic grating demodulator to the computer, power on and test the spectral signal quality, and perform static calibration and water flow testing.

[0039] In a specific implementation, as a preferred embodiment of the present invention, the pre-tensioning operation in step S2 includes: Apply pretension to each fiber Bragg grating and use UV-curing adhesive to temporarily fix both ends of the fiber Bragg grating to the positioning fixture to ensure that the grating section is straight; Four tensioned fiber Bragg gratings are placed into the corresponding rectangular microgrooves of the silicone substrate mold, ensuring that the center of the grating area is located in the central plane of the silicone substrate in the height direction. The silicone rubber, which is mixed and degassed in proportion, is poured into a mold to completely cover the fiber Bragg grating and rectangular microgroove. It is then cured in a 60°C oven for 2 hours to form an integrated structure of silicone matrix and fiber Bragg grating. After curing, the external fixing adhesive dots are cut off to release the pretension, so that the fiber Bragg grating remains taut under the constraint of the silicone to improve the response sensitivity and linearity.

[0040] In this embodiment, the design ensures that the four FBGs are spatially symmetrically distributed. When the substrate deforms due to the force transmission structure above, the local strain at the location of each FBG is different, thereby causing independent drift of their respective center wavelengths.

[0041] The present invention also provides a method of using the above-mentioned real-time vector flow velocity monitoring system, comprising: Step 1: Mechanical transformation. The water flow impacts the fan-shaped guide shield. The impact force of the water flow is decomposed according to the direction of the water flow and transmitted to the central force column and support rod. The support rod transmits the force of the water flow to the silicone matrix in the form of torque, causing the silicone matrix to produce asymmetric deformation. Step 2: Optical sensing. The deformation of the highly elastic silicone substrate causes the four fiber Bragg gratings embedded in the rectangular microgroove to generate a center wavelength shift corresponding to the strain state at their respective positions. The four fiber Bragg gratings each generate a first center wavelength shift. Second center wavelength drift Third center wavelength drift and fourth center wavelength drift Because the four fiber Bragg gratings are orthogonally symmetrically arranged at 90° to each other on the horizontal projection plane, water flow in different directions produces four-channel wavelength drift combinations with different characteristics. Step 3: Signal Acquisition and Calculation. The reflected light from the four fiber Bragg gratings is combined through a 4×1 fiber coupler. The fiber grating demodulator collects the data of the first, second, third, and fourth center wavelength drifts in real time. After the data is transmitted to the computing unit, the trained deep learning decoupling model processes the combination of the four-channel wavelength drifts and outputs a three-dimensional flow velocity vector.

[0042] In a specific implementation, as a preferred embodiment of the present invention, the deep learning decoupling model adopts a neural network algorithm to calculate the flow velocity, horizontal direction angle and vertical tilt angle through four-channel wavelength drift data decoupling.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A real-time vector velocity monitoring system based on fan blade guidance and FBG fiber optic sensing, comprising an integrated multi-channel vector sensing probe and a multi-channel fiber optic signal acquisition link, characterized in that: The integrated vector multi-channel sensing probe adopts a four-layer integrated vertical stacked structure. The layers are bonded together to form a continuous internal stress transmission path. From top to bottom, the layers are a flow-guiding sensing layer, a mechanical transmission layer, a sensing decoupling layer, and a base layer. The flow-guiding sensing layer is located at the top of the sensor and is a fan-shaped flow guide cover that directly withstands the impact of water flow, thereby achieving preliminary decomposition of the flow field vector and suppression of eddies. The mechanical transmission layer includes a central force-bearing column and a support rod, which serve as a rigid connecting rod between the flow-guiding sensing layer and the sensing decoupling layer, transmitting the resultant force of the water flow received by the flow-guiding sensing layer to the sensing decoupling layer. The sensing decoupling layer is the core sensing unit, comprising a highly elastic silicone substrate and four fiber Bragg gratings. The four fiber Bragg gratings are embedded in the silicone substrate in a four-point orthogonal symmetrical manner. The four fiber Bragg gratings are 90° apart on the horizontal projection plane, located at 0°, 90°, 180°, and 270° respectively. The centers of the grating regions of the four fiber Bragg gratings are located on the same horizontal plane in the longitudinal section and are equidistant from the radial distance of the central axis of the highly elastic silicone substrate. The center wavelengths of the four fiber Bragg gratings are uniformly distributed in the 1530nm to 1565nm band to ensure separation of the reflection spectrum without crosstalk. The base layer is used to fix and mount the entire sensor; The multi-channel fiber optic signal acquisition link includes a sensing probe, a 4×1 fiber coupler, and a fiber Bragg grating demodulator; the four fiber Bragg gratings of the sensing probe are connected to the fiber Bragg grating demodulator through the 4×1 fiber coupler.

2. The vector flow velocity real-time monitoring system based on the fan flow guiding and FBG optical fiber sensing according to claim 1, characterized in that, The fan-shaped fairing is connected to the upper end of the central force-bearing column by adhesive bonding. It consists of 10 identical blades evenly distributed around the circumference. Each blade is a streamlined airfoil with a chord length of 15mm, a maximum blade thickness of 3mm, and a vertical length of 4mm. Ten blades together form a fairing with an outer diameter of 25mm.

3. The vector flow velocity real-time monitoring system based on fan flow guiding and FBG optical fiber sensing according to claim 1, characterized in that, The central force-bearing column is a solid cylinder with a diameter of 8mm and a height of 10mm, and its lower end is provided with an adhesive surface; the central force-bearing column gathers the water flow impact force received by the fan-shaped guide shield into a resultant force and transmits it downward to the support rod.

4. The vector flow velocity real-time monitoring system based on fan flow guiding and FBG optical fiber sensing according to claim 1, characterized in that, The support rod is a cylindrical rod with a diameter of 3mm and a length of 15mm; the upper end of the support rod is fixed to the lower end of the central load-bearing column by high-strength epoxy structural adhesive; the lower end of the support rod is fixed to the center position of the upper surface of the high-elasticity silicone substrate by high-strength epoxy structural adhesive, and the connection is expanded with a flexible transition adhesive layer; the support rod transmits the force of water flow on the upper structure to the high-elasticity silicone substrate in the form of torque.

5. The real-time vector velocity monitoring system based on fan blade guidance and FBG fiber optic sensing according to claim 1, characterized in that, The silicone substrate is cylindrical with a diameter of 4 mm and a height of 25 mm. Inside the silicone substrate, along the circumferential direction, four rectangular microgrooves, each 2 mm deep and 1 mm wide, are pre-fabricated on a circle 10 mm from the central axis. These four microgrooves are at 90° intervals on the horizontal projection plane, corresponding to 0°, 90°, 180°, and 270° orientations, respectively, and are used to position four fiber Bragg gratings. All four fiber Bragg gratings are polyimide-coated fiber Bragg gratings with initial center wavelengths of 1540.0 nm, 1542.0 nm, 1544.0 nm, and 1546.0 nm, respectively.

6. The real-time vector velocity monitoring system based on fan blade guidance and FBG fiber optic sensing according to claim 1, characterized in that, Silicone rubber is coated around the connection between the support rod and the high-elasticity silicone substrate; the sensor probe is equipped with a streamlined shell, and the shell is filled with polyurethane elastomer to form a uniform waterproof protective skin with a thickness of 2mm to 3mm. The fan-shaped flow guide is partially exposed to the water flow; four optical fibers leading out from the side of the silicone substrate are integrated into an optical cable with a diameter of 3mm. The optical cable and the sensor shell are sealed with a through-type watertight joint, and the joint is filled with waterproof gel.

7. A method for preparing a real-time vector flow velocity monitoring system based on any one of claims 1-6, characterized in that, include: S1. Processing and manufacturing silicone substrate molds, flow guide molds, and packaging shell molds; S2. Position and pre-tension four fiber Bragg gratings in the silicone matrix mold, pour and cure the silicone, and demold to obtain a highly elastic silicone matrix with built-in fiber Bragg gratings. S3. The fan blades, central force-bearing column and support rod are manufactured using 3D printing technology. The fan blades, central force-bearing column and support rod are then glued together to form a rigid whole, forming a flow guiding and mechanical transmission structure composed of fan blade-type flow guide, central force-bearing column and support rod. S4. Align the lower end of the support rod with the center of the upper surface of the silicone substrate and fix it in place. Align the lower end of the support rod with the center of the upper surface of the high elastic silicone substrate and fix it with high-strength epoxy structural adhesive. Expand the contact area at the connection and set a flexible transition adhesive layer to avoid stress concentration and damage to the silicone substrate. Fix the flow guiding and mechanical transmission structure composed of fan-shaped flow guide, central force column and support rod to the high elastic silicone substrate to form an integrated vector multi-channel sensing probe. S5. Place the integrated vector multi-channel sensing probe into the packaging shell mold, pour polyurethane to form a protective layer, install the armored optical cable and watertight connector, and complete the overall packaging and waterproofing treatment. S6. Connect the fiber optic grating demodulator to the computer, power on and test the spectral signal quality, and perform static calibration and water flow testing.

8. The preparation method according to claim 7, characterized in that, The specific operations of pre-tensioning in step S2 include: Apply pretension to each fiber Bragg grating and use UV-curing adhesive to temporarily fix both ends of the fiber Bragg grating to the positioning fixture to ensure that the grating section is straight; Four tensioned fiber Bragg gratings are placed into the corresponding rectangular microgrooves of the silicone substrate mold, ensuring that the center of the grating area is located in the central plane of the silicone substrate in the height direction. The silicone rubber, which is mixed and degassed in proportion, is poured into a mold to completely cover the fiber Bragg grating and rectangular microgroove. It is then cured in a 60°C oven for 2 hours to form an integrated structure of silicone matrix and fiber Bragg grating. After curing, the external fixing adhesive dots are cut off to release the pretension, so that the fiber Bragg grating remains taut under the constraint of the silicone.

9. A method of using the real-time vector flow velocity monitoring system according to any one of claims 1-6, characterized in that, include: Step 1: Mechanical transformation. The water flow impacts the fan-shaped guide shield. The impact force of the water flow is decomposed according to the direction of the water flow and transmitted to the central force column and support rod. The support rod transmits the force of the water flow to the silicone matrix in the form of torque, causing the silicone matrix to produce asymmetric deformation. Step 2, Optical Sensing: The deformation of the highly elastic silicone substrate causes the four fiber Bragg gratings embedded in the rectangular microgroove to generate center wavelength drifts corresponding to the strain states at their respective positions. The four fiber Bragg gratings generate first, second, third, and fourth center wavelength drifts, respectively. Since the four fiber Bragg gratings are orthogonally symmetrically arranged at 90° to each other on the horizontal projection plane, water flow in different directions generates four-channel wavelength drift combinations with different characteristics. Step 3: Signal Acquisition and Calculation. The reflected light from the four fiber Bragg gratings is combined through a 4×1 fiber coupler. The fiber grating demodulator collects the data of the first, second, third, and fourth center wavelength drifts in real time. After the data is transmitted to the computing unit, the trained deep learning decoupling model processes the combination of the four-channel wavelength drifts and outputs a three-dimensional flow velocity vector.

10. The method of use according to claim 9, characterized in that, In step S3, the deep learning decoupling model uses a neural network algorithm to calculate the flow velocity, horizontal direction angle, and vertical tilt angle through four-channel wavelength drift data decoupling.

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