A fiber optic sensor for monitoring the flow direction of water around bridge piers

Abstract

The present invention provides a fiber optic sensor for monitoring the flow direction of water around bridge piers, belonging to the field of measurement technology. The fiber optic sensor for monitoring the flow direction of water around bridge piers includes an optical fiber, a stepped mirror, a flow direction tail rudder, a metal base, an optical fiber protective armor, an optical fiber fixing clamp, an inner cylinder, a flow direction axis, a flow direction mark, an outer hollow cylinder and a bearing. The device realizes real-time monitoring of the flow direction of water around bridge piers by observing the changes in the spectrum in the spectrometer and applying the Fabry-Perot fiber interference principle and geometric relationship, effectively analyzing the impact of water flow on the pier structure, and rationally formulating maintenance measures, thereby extending the service life of the bridge structure. The present invention has strong anti-interference ability, high precision, and strong adaptability, and has broad application prospects and promotion markets.

Description

Technical Field

[0001] The invention relates to an optical fiber sensor for monitoring the flow direction of water around a bridge pier, and belongs to the field of measurement technology. Background Art

[0002] In recent years, my country's highway bridge construction has achieved remarkable achievements. The construction of bridges has developed in the process of constantly resisting external damage. Under the influence of the natural environment, water flow is one of the main causes of bridge structure damage. When the actual water flow exceeds the design standard value of bridge construction, the water flow will wash the bridge deck, which may damage the internal structure of the bridge deck and affect the durability and stability of the structure. Therefore, real-time monitoring of the flow direction of the water flow and timely maintenance and repair of the structure are conducive to improving the service life of the structure.

[0003] At present, the sensors used to monitor fluid flow direction include mechanical, hot wire, electromagnetic, Doppler optical, and ray radiation. The principle of the commonly used heat transfer microfluidic sensor is to use external physical quantities to change the temperature distribution in the flow field, and convert the temperature change into an electrical signal output. It has problems such as high power consumption and long response time. The mechanical flow direction sensor uses the rotation of a mechanical rotor to measure the flow direction of the fluid, and has low sensitivity. The electromagnetic flow direction sensor is a sensor that uses the law of electromagnetic induction to measure the flow rate, and has high requirements for the magnetic field distribution. The ray radiation sensor is a sensor that uses radioactive isotopes for measurement and is usually not suitable for fixed-point monitoring.

[0004] Due to the complexity of the water flow environment where the water structure is located, it is difficult to measure the flow direction. In recent years, optical fiber has been widely used in the field of measurement technology due to its advantages such as small size, high sensitivity, high accuracy, anti-electromagnetic interference, and small size and lightness. Therefore, it is very necessary to design a water flow direction optical fiber sensor with high accuracy, good stability, and real-time monitoring, which can provide technical support for the construction and safe service of water structures. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a fiber optic sensor for monitoring the flow direction of water around bridge piers, the purpose of which is to monitor the flow direction of water around long-span bridges in real time, thereby avoiding safety accidents and increasing the service life of water structures.

[0006] The technical solution of the present invention:

[0007] A fiber optic sensor for monitoring the flow direction of water comprises an optical fiber 1, a stepped mirror 2, a flow direction tail rudder 3, a metal base 4, an optical fiber protection armor 5, an optical fiber fixing clamp 6, an inner cylinder 7, a flow direction axis 8, a flow direction mark 9, an outer hollow cylinder 10, and a bearing 11.

[0008] Design 1:

[0009] The optical fiber 1 is fixed to the top of the outer hollow cylinder 10 by the optical fiber fixing clamp 6. The angle between the optical fiber fixing clamp 6 and the axis of the outer hollow cylinder 10 and the inclination angle of the stepped mirror 2 are consistent, so that the end of the optical fiber 1 is always perpendicular to the stepped mirror 2 during the rotation of the outer hollow cylinder 10. The initial position of the optical fiber 1 is located outside the circumference of the stepped mirror 2 on the upper surface of the inner cylinder 7, and maintains a certain distance from the inner cylinder 7.

[0010] The optical fiber protection armor 5 is used to protect the optical fiber 1;

[0011] The metal base 4, the inner cylinder 7, the outer hollow cylinder 10 and the bearing 11 are concentric and coaxial, and the stepped mirror surface 2 maintains a certain distance from the top of the outer hollow cylinder 10;

[0012] The flow fin 3, the flow axis 8, the flow mark 9 and the outer hollow cylinder 10 can be connected by welding, and the flow fin 3, the flow axis 8 and the flow mark 9 are located in the same horizontal direction;

[0013] The bottom radius of the metal base 4 is larger than the bottom radius of the outer hollow cylinder 10, the bottom surfaces of the outer hollow cylinder 10 and the inner cylinder 7 are flush, and the height of the outer hollow cylinder 10 is higher than the inner cylinder 7;

[0014] The step-type mirror surface 2 can be vacuum metal sputtered or polished, and the inclination angle of the step-type mirror surface 2 is adjustable;

[0015] The end face of the optical fiber 1 and the stepped mirror 2 form a Fabry-Perot cavity. When the flow vane 9 rotates along with the flow direction of the water, the outer hollow cylinder 10 is driven to rotate accordingly, further causing the distance between the end of the optical fiber 1 and the stepped mirror 2, i.e., the cavity length of the Fabry-Perot cavity, to change accordingly.

[0016] The metal base 4, the outer hollow cylinder 10, and the bearing 11 seal the entire monitoring device and protect the optical fiber Fabry-Perot interferometer;

[0017] The bearing 11 is located on the bottom surface of the outer hollow cylinder 10, and the bearing 11 is provided by drilling the metal base 4 to support and drive the outer hollow cylinder 10;

[0018] The flow direction rudder 3, flow direction shaft 8 and flow direction indicator 9 constitute a fluid direction indicator, and the rotation angle is 360°;

[0019] The cylinder radius of the inner cylinder 7, the inclination angle of the stepped mirror 2, the distance from the end face of the optical fiber 1 to the inner cylinder 7 and the length of the flow axis 8 can be adjusted according to the required sensitivity.

[0020] Design 2 has the following differences from Design 1:

[0021] The optical fiber 1 and the optical fiber protection armor 5 pass through the metal base 4 and the inner cylinder 7, and form a Fabry-Perot cavity with the stepped mirror 2, and the optical fiber 1 is located below the outer side of the circumference of the stepped mirror 2;

[0022] The optical fiber 1 and the stepped mirror 2 have the same inclination angle, so that the end of the optical fiber 1 always remains perpendicular to the stepped mirror 2 during the rotation of the outer hollow cylinder 10;

[0023] The end face of the optical fiber 1 and the stepped mirror 2 form a Fabry-Perot cavity. When the flow direction indicator 9 rotates along with the flow direction of the fluid, the stepped mirror 2 is driven to rotate accordingly, further causing the distance between the end of the optical fiber 1 and the stepped mirror 2, that is, the cavity length of the Fabry-Perot cavity to change accordingly.

[0024] Working principle of the present invention:

[0025] The present invention is placed in the water flow around the bridge pier to be measured. The flow of water causes the fluid pointer to rotate accordingly, causing the length of the Fabry-Perot cavity formed by the step mirror 2 and the optical fiber end face to change. The change in the cavity length is monitored by a spectrometer to determine the direction of the water flow. The core of the present invention is the working principle of the Fabry-Perot optical fiber sensor. The Fabry-Perot cavity is formed by the step mirror 2 and the optical fiber end face. The incident light propagates in the optical fiber 1. The reference light reflection occurs with the optical fiber end face for the first time, and the sensing reflection occurs with the step mirror 2 for the second time. The intensity expression of the interference signal I generated by the reflected light is:

[0026]

[0027] Where, I1 and I2 are the intensities of the reflected light input from the two reflection surfaces; n is the refractive index of the intermediate medium (air); δ is the length of the Fabry-Perot interferometer cavity; λ is the wavelength, is the phase difference between the two reflected lights.

[0028] The distance between the end of the optical fiber 1 and the axis of the inner cylinder 7 is R, the inclination angle of the step mirror 2 is β, and the initial position of the optical fiber 1 and the initial distance (initial cavity length) of the step mirror 2 is δ0. When the flow direction tester rotates at an angle θ, the relationship between the Fabry-Perot cavity length Δδ and the flow direction tester rotation angle θ can be expressed as:

[0029]

[0030] Based on the above principle, the rotation angle θ of the flow direction tester can be determined by the change of the Fabry-Perot chamber length Δδ.

[0031] Beneficial effects of the present invention:

[0032] (1) The present invention realizes real-time monitoring of the flow direction of water around the bridge pier by monitoring the change in the cavity length of the Fabry-Perot optical fiber sensor;

[0033] (2) The present invention can meet the sensitivity required by actual engineering by changing the cylindrical radius of the inner cylinder, the inclination angle of the stepped mirror, the distance from the optical fiber end face to the inner cylinder, and the length of the flow axis;

[0034] (3) The flow direction tester of the present invention has a rotation angle of 360°, which can realize the monitoring function of 360° non-directional water flow direction;

[0035] (4) The present invention has a simple structure, low price, strong applicability, and broad application prospects and promotion market. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Two structural schematic diagrams of optical fiber sensors used for monitoring the flow direction of water around bridge piers according to the present invention;

[0037] Figure 2 AA cross-section diagram of two optical fiber sensor structures used to monitor the flow direction of water around bridge piers;

[0038] Figure 3 BB cross-section diagram of two optical fiber sensor structures used to monitor the flow direction of water around bridge piers;

[0039] Figure 4 It is a schematic diagram of the placement of the present invention for monitoring the flow velocity of flowing water at bridge piers.

[0040] In the figure: 1 optical fiber; 2 stepped mirror; 3 flow direction rudder; 4 metal base; 5 optical fiber protection armor; 6 optical fiber fixing clamp; 7 inner cylinder; 8 flow direction axis; 9 flow direction mark; 10 outer hollow cylinder; 11 bearing. DETAILED DESCRIPTION

[0041] The specific implementation of the optical fiber sensor for monitoring the flow direction of water around bridge piers will be described below in conjunction with the accompanying drawings.

[0042] As shown in the figure, the present invention provides a fiber optic sensor for monitoring the flow direction of water around bridge piers, including an optical fiber 1, a stepped mirror 2, a flow direction tail rudder 3, a metal base 4, an optical fiber protection armor 5, an optical fiber fixing clamp 6, an inner cylinder 7, a flow direction axis 8, a flow direction mark 9, an outer hollow cylinder 10, and a bearing 11.

[0043] For design plan 1:

[0044] The optical fiber 1 is fixed to the top of the outer hollow cylinder 10 by the optical fiber fixing clamp 6. The angle between the optical fiber fixing clamp 6 and the axis of the outer hollow cylinder 10 and the inclination angle of the stepped mirror 2 are consistent, so that the end of the optical fiber 1 is always perpendicular to the stepped mirror 2 during the rotation of the outer hollow cylinder 10. The initial position of the optical fiber 1 is located outside the circumference of the stepped mirror 2 on the upper surface of the inner cylinder 7, and maintains a certain distance from the inner cylinder 7.

[0045] The optical fiber protection armor 5 is used to protect the optical fiber 1;

[0046] The metal base 4, the inner cylinder 7, the outer hollow cylinder 10 and the bearing 11 are concentric and coaxial, and the stepped mirror surface 2 maintains a certain distance from the top of the outer hollow cylinder 10;

[0047] The flow fin 3, the flow axis 8, the flow mark 9 and the outer hollow cylinder 10 can be connected by welding, and the flow fin 3, the flow axis 8 and the flow mark 9 are located in the same horizontal direction;

[0048] The bottom radius of the metal base 4 is larger than the bottom radius of the outer hollow cylinder 10, the bottom surfaces of the outer hollow cylinder 10 and the inner cylinder 7 are flush, and the height of the outer hollow cylinder 10 is higher than the inner cylinder 7;

[0049] The step-type mirror surface 2 can be vacuum metal sputtered or polished, and the inclination angle of the step-type mirror surface 2 is adjustable;

[0050] The end face of the optical fiber 1 and the stepped mirror 2 form a Fabry-Perot cavity. When the flow vane 9 rotates along with the flow direction of the water, the outer hollow cylinder 10 is driven to rotate accordingly, further causing the distance between the end of the optical fiber 1 and the stepped mirror 2, i.e., the cavity length of the Fabry-Perot cavity, to change accordingly.

[0051] The metal base 4, the outer hollow cylinder 10, and the bearing 11 seal the entire monitoring device and protect the optical fiber Fabry-Perot interferometer;

[0052] The bearing 11 is located on the bottom surface of the outer hollow cylinder 10, and the bearing 11 is provided by drilling the metal base 4 to support and drive the outer hollow cylinder 10;

[0053] The flow direction rudder 3, flow direction shaft 8 and flow direction indicator 9 constitute a fluid direction indicator, and the rotation angle is 360°;

[0054] The cylinder radius of the inner cylinder 7, the inclination angle of the stepped mirror 2, the distance from the end face of the optical fiber 1 to the inner cylinder 7 and the length of the flow axis 8 can be adjusted according to the required sensitivity.

[0055] Design 2 has the following differences from Design 1:

[0056] The optical fiber 1 and the optical fiber protection armor 5 pass through the metal base 4 and the inner cylinder 7, and form a Fabry-Perot cavity with the stepped mirror 2, and the optical fiber 1 is located below the outer side of the circumference of the stepped mirror 2;

[0057] The optical fiber 1 and the stepped mirror 2 have the same inclination angle, so that the end of the optical fiber 1 always remains perpendicular to the stepped mirror 2 during the rotation of the outer hollow cylinder 10;

[0058] The end face of the optical fiber 1 and the stepped mirror 2 form a Fabry-Perot cavity. When the flow direction indicator 9 rotates along with the flow direction of the fluid, the stepped mirror 2 is driven to rotate accordingly, further causing the distance between the end of the optical fiber 1 and the stepped mirror 2, that is, the cavity length of the Fabry-Perot cavity to change accordingly.

[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optical fiber sensor for monitoring the flow direction of water around a bridge pier, characterized in that: The optical fiber sensor for monitoring the flow direction of flowing water comprises an optical fiber (1), a stepped mirror (2), a flow direction tail rudder (3), a metal base (4), an optical fiber protective armor (5), an optical fiber fixing clamp (6), an inner cylinder (7), a flow direction axis (8), a flow direction indicator (9), an outer hollow cylinder (10) and a bearing (11); The metal base (4), the outer hollow cylinder (10) and the bearing (11) seal the entire monitoring device and protect the optical fiber Fabry-Perot interferometer; The metal base (4), the inner cylinder (7), the outer hollow cylinder (10) and the bearing (11) are concentric and coaxial, and the stepped mirror surface (2) maintains a certain distance from the top of the outer hollow cylinder (10); The end of the optical fiber (1) always remains perpendicular to the stepped mirror surface (2) during the rotation of the outer hollow cylinder (10); The flow direction rudder (3), flow direction axis (8) and flow direction indicator (9) are located in the same horizontal direction; The bottom radius of the metal base (4) is greater than the bottom radius of the outer hollow cylinder (10), the bottom surfaces of the outer hollow cylinder (10) and the inner cylinder (7) are flush, and the height of the outer hollow cylinder (10) is higher than that of the inner cylinder (7); The metal base (4) is provided with a bearing (11) for driving the outer hollow cylinder (10); The end face of the optical fiber (1) and the stepped mirror (2) form a Fabry-Perot cavity. When the flow vane (9) rotates along with the flow direction of the fluid, the outer hollow cylinder (10) is driven to rotate accordingly, further causing the distance between the end of the optical fiber (1) and the stepped mirror (2), i.e., the cavity length of the Fabry-Perot cavity, to change accordingly. The optical fiber (1) and the optical fiber protection armor (5) pass through the hollow cylinder (10) to form a Fabry-Perot cavity with the stepped mirror (2), or the optical fiber (1) and the optical fiber protection armor (5) pass through the metal base (4) and the inner cylinder (7) to form a Fabry-Perot cavity with the stepped mirror (2).

2. The optical fiber sensor for monitoring the flow direction of water around a bridge pier according to claim 1, characterized in that: The optical fiber (1) is fixed to the top of the outer hollow cylinder (10) by means of an optical fiber fixing clamp (6). The axial angle of the optical fiber fixing clamp (6) and the outer hollow cylinder (10) is consistent with the inclination angle of the stepped mirror surface (2). In this way, the end of the optical fiber (1) always remains perpendicular to the stepped mirror surface (2) during the rotation of the outer hollow cylinder (10). The initial position of the optical fiber (1) is located outside the circumference of the stepped mirror surface (2) on the upper surface of the inner cylinder (7) and maintains a certain distance from the inner cylinder (7).

3. The optical fiber sensor for monitoring the flow direction of water around a bridge pier according to claim 1 or 2, characterized in that: The flow direction rudder (3), the flow direction shaft (8), the flow direction indicator (9) and the outer hollow cylinder (10) are connected by welding.

4. The optical fiber sensor for monitoring the flow direction of water around a bridge pier according to claim 1 or 2, characterized in that: The stepped mirror surface (2) is formed by vacuum metal sputtering or grinding and polishing.

5. The optical fiber sensor for monitoring the flow direction of water around a bridge pier according to claim 1 or 2, characterized in that: The optical fiber protection armor (5) is used to protect the optical fiber (1).

6. The optical fiber sensor for monitoring the flow direction of water around a bridge pier according to claim 1 or 2, characterized in that: The bearing (11) is located on the bottom surface of the outer hollow cylinder (10).

7. The optical fiber sensor for monitoring the flow direction of water around a bridge pier according to claim 1, characterized in that: The flow direction rudder (3), the flow direction shaft (8) and the flow direction indicator (9) constitute a fluid direction indicator, and the rotation angle is 360°.

8. The optical fiber sensor for monitoring the flow direction of water around a bridge pier according to claim 1 or 2, characterized in that: The cylindrical radius of the inner cylinder (7), the inclination angle of the stepped mirror (2), the distance from the end face of the optical fiber (1) to the inner cylinder (7), and the length of the flow axis (8) can be adjusted according to the required sensitivity.

9. The optical fiber sensor for monitoring the flow direction of water around a bridge pier according to claim 1, characterized in that: The bearing (11) reduces sliding friction, making the rotation smoother and the measurement result more accurate.

10. The optical fiber sensor for monitoring the flow direction of water around a bridge pier according to claim 1 or 2, characterized in that: The optical fiber (1) is located above the outer side of the circumference of the stepped mirror surface (2) or below the outer side of the circumference of the stepped mirror surface (2).

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