Fluid wall shear pressure stress composite array sensor chip

Abstract

The invention discloses a fluid wall shear pressure stress composite array sensor chip, and belongs to the technical field of MEMS sensors. Comprising a plurality of shear stress sensors and pressure stress sensors which are integrated on a chip, the overall arrangement array of the shear stress sensors is in a regular cross shape, the overall arrangement array of the pressure stress sensors is in an X shape, and the two arrays are concentrically superposed to obtain a grid type array layout; the pressure sensor is arranged in the center of the grid-type array, the shear stress sensors are arranged in an outward radiation mode in the regular cross direction with the center pressure sensor as the radiation center and used for measuring the two-dimensional shear stress, and the pressure stress sensors are arranged in an outward radiation mode in the X-shaped direction with the center pressure sensor as the radiation center and used for measuring the two-dimensional shear stress. Gradient pressure is measured. According to the method, the problem that actual flow field stress distribution is difficult to fully reflect by single-point measurement in a complex fluid environment is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of MEMS sensors, and in particular relates to a fluid wall shear-compression stress composite array sensor chip. Background Art

[0002] Wall shear stress and wall pressure stress have always been two important physical quantities in fluid dynamics research. Wall shear stress is affected by fluid viscosity and velocity gradient in the boundary layer, and pressure pulsation is caused by velocity field disturbance in the boundary layer. Realizing the simultaneous measurement of wall shear stress and pressure stress can effectively obtain the pulsation characteristics of the boundary layer evolution process, grasp the boundary layer flow noise information, and provide important data support for the optimization design of aircraft / vehicle drag reduction, stealth and noise reduction. Since wall shear stress and wall pressure stress have the characteristics of small value, high dynamics, and small flow characteristic size, traditional measurement methods are limited by low sensitivity, large volume, and high temperature resistance. It is also difficult for a single device to simultaneously meet the accurate measurement of two physical quantities.

[0003] Optical testing technology has significant advantages in shear stress and pressure measurement, mainly reflected in its non-contact measurement, high resolution and anti-interference ability. First of all, optical testing technology does not require direct contact with the physical surface being measured, avoiding the mechanical interference and surface damage that may be caused by traditional sensors, and is particularly suitable for use in extreme environments such as high temperature and high-speed flow. Secondly, optical testing technology has high spatial and temporal resolution, and can accurately capture tiny stress changes and transient phenomena, meeting the needs of high-precision measurement of dynamic processes. In addition, the optical system is insensitive to electromagnetic interference, which significantly improves the robustness of the measurement process and the reliability of the data, and shows irreplaceable advantages in applications with high precision, long-term monitoring and complex environments.

[0004] Currently, in the relevant technology, a single compressive stress sensor or a two-dimensional shear stress sensor is used for testing, and the single compressive stress sensor or the two-dimensional shear stress sensor is usually arbitrarily arranged in an array. Since it is an array of a single sensor, firstly, errors will occur in the installation, and secondly, single-point measurement is difficult to fully reflect the actual flow field stress distribution. Therefore, in a complex fluid environment, a single array-arranged compressive stress sensor or a two-dimensional shear stress sensor cannot obtain accurate measurement results. Summary of the invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the prior art, the present invention provides a fluid wall shear and compressive stress composite array sensor chip, which combines the two-dimensional shear stress sensor and the compressive stress sensor of the fluid wall into an array composite to obtain an integrated shear and compressive stress sensor array structure capable of measuring gradient pressure; the two-dimensional shear stress sensor and the compressive stress sensor with similar structure are arranged in a grid array, which not only reduces the volume and weight of the sensor, but also reduces the assembly error. Multiple sensors can collect data synchronously at different positions to achieve mutual correction of data and high spatial resolution measurement. The present invention solves the problem that single-point measurement is difficult to fully reflect the actual flow field stress distribution in a complex fluid environment, improves the measurement accuracy, and also provides an accurate test method for stress changes in fields such as fluid mechanics, meeting the multi-point stress measurement needs in a complex fluid environment.

[0007] The technical solution of the present invention is: a fluid wall shear and pressure stress composite array sensor chip, including a plurality of shear stress sensors and pressure stress sensors integrated on the chip, the overall arrangement formation of the shear stress sensors is in the shape of a right cross, the overall arrangement formation of the pressure stress sensors is in the shape of an X, and the two formations are concentrically superimposed to obtain a square array layout; the center position of the square array is a pressure sensor, and a plurality of shear stress sensors are arranged radiating outward along the right cross direction with the central pressure sensor as the radiation center to measure two-dimensional shear stress, and a plurality of pressure stress sensors are arranged radiating outward along the X direction with the central pressure sensor as the radiation center to measure gradient pressure.

[0008] A further technical solution of the present invention is that the shear stress sensor and the compressive stress sensor are integrated and processed on a chip through MEMS processing technology.

[0009] A further technical solution of the present invention is that the shear stress sensor and the compressive stress sensor both include a support layer, a cavity and a structural layer, the upper surface of the support layer and the lower surface of the structural layer are both provided with a reflective film, and the surface of the cavity is provided with an anti-reflective coating.

[0010] A further technical solution of the present invention is that: the support layer of the compressive stress sensor is provided with a plurality of through holes for positioning and fixing the optical fiber, and the internal reflection film is a metal reflection film.

[0011] A further technical solution of the present invention is: the structural layer of the shear stress sensor is a floating structure, and its internal reflection film is a grating film; the floating structure includes an elastic beam, a floating element, and a fixed anchor point, and the floating element is connected to the fixed anchor point through a circumferentially arranged elastic beam, which can drive the grating film installed on the lower surface of the floating element to produce displacement.

[0012] A further technical solution of the present invention is: the reflective film is a silicon nitride film, a chromium film layer and a gold film layer from bottom to top, and a dielectric multilayer film with alternating low and high refractive indices is plated on the surface of the gold film layer, in the order of low refractive medium layer / high refractive medium layer / low refractive medium layer / high refractive medium layer, and the thickness of each layer is λ / 4.

[0013] A further technical solution of the present invention is: the low-refractive dielectric layer of the dielectric multilayer film is Al2O3, and the high-refractive dielectric layer is ZrO2, which is 120nmAl2O3 / 100nmZrO2 / 120nmAl2O3 / 100nmZrO2 respectively.

[0014] A method for measuring the gradient pressure of a fluid wall shear-compression stress composite array sensor chip, the specific steps are as follows:

[0015] Arrange multiple compressive stress sensors in an X shape on the chip, and the spacing between adjacent compressive stress sensors in a single radial arrangement direction is equal;

[0016] Through experiments, it is found that the measured values ​​of each level of pressure stress sensor from the center to the outside show a linear gradient change law;

[0017] Identify outliers and system errors based on the gradient descent variation rule, and determine the measurement points where error values ​​are generated;

[0018] After the error is identified and confirmed, the pressure data of each measuring point is corrected by interpolation or weighted average method to obtain accurate measurement values.

[0019] A further technical solution of the present invention is: the method for identifying abnormal values ​​and systematic errors is:

[0020] The identification of the outlier, for the compressive stress sensors located in the same radiation direction, compares the measured difference of the adjacent compressive stress sensors with the threshold value obtained based on the linear gradient descent change law, and judges it as an outlier when the difference exceeds the threshold value; for the compressive stress sensors located at the same circumferential gradient level, the measured values ​​should be consistent, if there is a difference, the point is judged as an outlier;

[0021] The identification of the system error compares the identified abnormal value with the normal value, screens the deviation range to distinguish between the real error and the instantaneous abnormality caused by noise or environmental interference, and identifies the measurement point of the real error as the system error.

[0022] A further technical solution of the present invention is: the method for correcting the pressure data of each measuring point is to interpolate between the measuring point identified as an outlier and the normal value measuring points adjacent to it on both sides, and determine the true pressure value of the outlier by multi-point interpolation; in this way, each outlier is corrected to obtain an effective test of the pulsating characteristics of the turbulent boundary layer formation and separation process.

[0023] Beneficial Effects

[0024] The beneficial effects of the present invention are as follows: the fluid wall shear and compressive stress composite array sensor chip of the present invention, on the one hand, adopts MEMS technology to integrate the two-dimensional shear stress sensor and the compressive stress sensor of the fluid wall on the same millimeter-level chip using an integrated synchronous manufacturing process, thereby simplifying the processing flow. On the other hand, the grid array layout not only reduces the volume and weight of the sensor, but also reduces the assembly error; multiple sensors can also collect data synchronously at different positions to achieve mutual correction of data and high spatial resolution measurement. This not only improves the measurement accuracy, but also provides a precise test method for stress changes in fields such as fluid mechanics, meeting the needs of multi-point stress measurement in complex fluid environments. The specific advantages are analyzed as follows:

[0025] 1. The grid array design can obtain pressure data from multiple spatial points and calculate the pressure gradient by differential calculation. The shear stress sensor at the centerline position can measure two-dimensional shear stress in orthogonal directions, thereby comprehensively obtaining the stress distribution in the fluid.

[0026] 2. There is no circuit structure inside the chip, which can be used not only in extreme high temperature environments, but also in the measurement of underwater fluid stress. This is suitable for the study of complex flow phenomena, and for effectively testing the pulsation characteristics of the formation and separation process of the turbulent boundary layer, laying the foundation for effectively evaluating the friction resistance and flow noise of the aerodynamic structure of aircraft / craft.

[0027] 3. The pressure gradient measurement method can directly reflect the pressure changes of the fluid at different spatial positions, and provide basic data for analyzing flow characteristics. In complex flow fields, pressure gradients often affect the flow direction, velocity distribution and boundary layer characteristics of the fluid, which is of key significance to the study of turbulence, separation phenomena, etc. Therefore, the dynamic behavior of the fluid can be more accurately grasped by measuring the pressure gradient, which is particularly important for fields such as aerospace that have strict requirements on aerodynamic characteristics and flow control. The present invention measures the pressure gradient through a multi-point layout of a palace-shaped array sensor, which can achieve high spatial resolution monitoring, so that the system can obtain detailed pressure change information. In addition, the palace-shaped array layout can realize mutual correction of data, effectively reduce single-point measurement errors through multi-point sampling and differential calculation, and improve measurement accuracy and data reliability. This method not only improves the comprehensiveness of the measurement, but also reduces the influence of external interference on the measurement results through self-calibration, and is particularly suitable for precise monitoring in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is an array top view of a fluid wall shear and compressive stress composite array sensor chip in an embodiment of the present invention;

[0029] Figure 2 A bottom view of a floating structure layer of a shear stress sensor according to an embodiment of the present invention;

[0030] Figure 3 A top view of a support layer on which a shear stress sensor floats in an embodiment of the present invention;

[0031] Figure 4 A bottom view of a compressive stress sensor structure layer in an embodiment of the present invention;

[0032] Figure 5 A top view of a compressive stress sensor support layer in an embodiment of the present invention;

[0033] Figure 6 This is an AA cross-sectional view of a fluid wall shear and compressive stress composite array sensor chip in an embodiment of the present invention;

[0034] Figure 7 Schematic diagram of a 4×4 grid array structure in an embodiment of the present invention.

[0035] Explanation of the accompanying drawings: 1. compressive stress sensor; 2. shear stress sensor; 3. elastic beam; 4. floating element; 5. cavity; 6. grating film; 7. fixed anchor point; 8. metal reflective film; 9. through hole; 10. floating structure; 11. structural layer; 12. supporting layer. DETAILED DESCRIPTION

[0036] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0038] Based on the problem that the prior art uses a separate pressure stress sensor or a two-dimensional shear stress sensor for testing, which will cause errors in installation and is difficult to fully reflect the actual flow field stress distribution, resulting in an inability to obtain accurate measurement results, the present invention provides a fluid wall shear and pressure stress composite array sensor chip, including a plurality of shear stress sensors and pressure stress sensors integrated on the chip, the overall arrangement formation of the shear stress sensors is in a right cross shape, the overall arrangement formation of the pressure stress sensors is in an X shape, and the two formations are concentrically superimposed to obtain a square array layout; the center position of the square array is a pressure sensor, a plurality of shear stress sensors are arranged radiating outward along the right cross direction with the central pressure sensor as the radiation center, so as to measure the two-dimensional shear stress, and a plurality of pressure stress sensors are arranged radiating outward along the X direction with the central pressure sensor as the radiation center, so as to measure the gradient pressure.

[0039] Specifically, the chip is composed of an optical compressive stress sensor and a shear stress sensor. The two sensors have similar structures, including a support layer, a cavity and a structural layer from bottom to top, and can be processed by MEMS processing technology to achieve integrated synchronous structure. A reflective film is provided on the upper surface of the support layer to reduce the crosstalk of external light sources; an anti-reflective coating is provided on the surface of the cavity to enhance the contrast of the reflective film, and the area of ​​the anti-reflective coating is larger than that of the reflective film. A reflective film is provided on the lower surface of the structural layer for receiving and reflecting optical signals.

[0040] Specifically, the reflective film of the pressure stress sensor is a metal reflective film, and the reflective film of the shear stress sensor is a grating film structure. The metal reflective film and the grating film structure can be processed synchronously by MEMS graphic sputtering metal film process. Using a metal film with high reflectivity as a grating can improve the sensitivity of the sensor, but under the high temperature condition of 350°C, the electrostatic repulsion between gold molecules of the gold grating film is weakened, while the interaction forces such as van der Waals force are enhanced, thereby promoting the mutual attraction of molecules, forming clusters and clumps, and affecting the intensity of reflected light. In order to suppress the agglomeration effect of gold and further improve the reflection efficiency of the grating film at high temperature, a dielectric layer film is plated on the gold grating. Based on the theory of the metal-dielectric reflective film model, a dielectric multilayer film with alternating high and low refractive indices and each layer λ / 4 thick is plated on the metal film to improve the reflectivity and high temperature resistance of the gold grating film. In practical applications, low-refractive-index aluminum oxide (Al2O3) and high-refractive-index (ZrO2) can be used in combination. This sensor is plated with 120nmAl2O3 / 100nmZrO2 / 120nmAl2O3 / 100nmZrO2 on the gold grating film to ensure that the gold grating film does not agglomerate above 400°C and still has high reflectivity.

[0041] Specifically, the pressure sensor is provided with a plurality of through holes in the support layer for positioning and fixing the optical fiber. The structural layer of the shear stress sensor is provided with a floating structure, and the floating structure is located above the concave cavity.

[0042] The present invention provides a method for measuring the gradient pressure of a fluid wall shear and compressive stress composite array sensor chip, and the specific steps are as follows:

[0043] Step 1: Arrange a plurality of compressive stress sensors in an X shape on the chip, and the spacing between adjacent compressive stress sensors in a single radial arrangement direction is equal;

[0044] Step 2: Through experiments, it is obtained that the measured values ​​of each level of pressure stress sensor from the central pressure stress sensor to the outside show a linear gradient change law;

[0045] Step 3: Identify outliers and system errors based on the gradient descent variation rule, and determine the measurement point where the error value is generated;

[0046] Specifically, the identification of the outlier, for the compressive stress sensors located in the same radiation direction, compares the measured difference between the adjacent compressive stress sensors with the threshold value obtained based on the linear gradient descent change law, and judges it as an outlier when the difference exceeds the threshold value; for the compressive stress sensors located at the same circumferential gradient level, the measured values ​​should be consistent, if there is a difference, the point is judged as an outlier;

[0047] The identification of the system error compares the identified abnormal value with the normal value, screens the deviation range to distinguish between the real error and the instantaneous abnormality caused by noise or environmental interference, and identifies the measurement point of the real error as the system error.

[0048] Step 4: After the error is identified and confirmed, the pressure data of each measuring point is corrected by interpolation or weighted average method to obtain an accurate measurement value.

[0049] Specifically, the method for correcting the pressure data of each measuring point is to interpolate between the measuring point identified as an outlier and the normal value measuring points adjacent to it on both sides, and determine the true pressure value of the outlier by multi-point interpolation; in this way, each outlier is corrected to obtain an effective test of the pulsation characteristics of the turbulent boundary layer formation and separation process.

[0050] The above technical solution is further described below with reference to examples and drawings:

[0051] Reference Figure 1 As shown, the present embodiment of a fluid wall shear and pressure stress composite array sensor chip includes a plurality of pressure stress sensors 1 and a shear stress sensor 2, and the two sensors are arranged on the same millimeter-level chip in a 3×3 grid array structure; the pressure stress sensor 1 is arranged at the diagonal position of the grid array, and each pressure sensor unit can independently measure the pressure value at its position, and by accurately controlling the position and spacing of each sensor unit in the array, the pressure data of multiple spatial points can be obtained. By performing differential calculation on these data, the pressure change of the fluid between different positions can be obtained, thereby realizing the measurement of the pressure gradient; the shear stress sensor 2 is arranged at the two center line positions in the X and Y directions of the array structure, and the shear stress sensor should be arranged vertically in the grid array structure according to the sensitive direction to realize the measurement of two-dimensional shear stress.

[0052] Reference Figure 6 As shown, the pressure sensor 1 and the shear stress sensor 2 each include a support layer 12, a cavity 5 and a structural layer 11 from bottom to top, and the support layer 12 is connected to the structural layer 11 by anodic bonding. A reflective film is provided on the lower surface of the structural layer 11 for receiving and reflecting optical signals. The reflective film of the pressure stress sensor 1 is a metal reflective film 8, and the reflective film of the shear stress sensor 2 is a grating film 6. The metal reflective film 8 and the grating film 6 can be patterned by photolithography and sputtering metal films through the same mask.

[0053] In this embodiment, the material of the structural layer 11 of the shear stress sensor 2 is 40-50 um silicon. Figure 2As shown, the shear stress sensor 2 is provided with a floating structure 10 on the structural layer 11. The floating structure 10 is located above the concave cavity 5. The floating structure 10 is composed of a plurality of elastic beams 3, a floating element 4, and a plurality of fixed anchor points 7. The floating element 4 is movably arranged on the fixed anchor points 7 through the elastic beams 3. The thickness of the floating element 4 is 20-30um. The lower surface of the floating element has a grating film 6 with a thickness of 320-420nm. The grating film 6 is composed of a 100-120nm silicon nitride film, a 20-50nm chromium film layer, and a 200-250nm gold film layer. The lower surface of the structural layer 11 is provided with a concave cavity 5. The depth of the concave cavity 5 is 20-30um, and the area of ​​the concave cavity 5 is larger than that of the floating element 4. The area of ​​the floating element 4 is larger than that of the grating film 6.

[0054] In this embodiment, the material of the structural layer 11 of the compressive stress sensor 1 is 40-50 um silicon, and a cavity 5 is provided on the lower surface of the structural layer 11. The depth of the cavity 5 is 20-30 um. Figure 4 As shown, the lower surface of the structural layer 11 is also provided with a metal reflective film 8 with a thickness of 320-420nm, the metal reflective film 8 is composed of a 100-120nm silicon nitride film, a 20-50nm chromium film layer and a 200-250nm gold film layer, and the area of ​​the cavity 5 is larger than the metal reflective film 8. Figure 5 As shown, a plurality of through holes 9 are provided in the support layer 12 of the pressure sensor 1 for positioning and fixing the optical fiber.

[0055] In this embodiment, refer to Figure 3 and Figure 5 As shown, the material of the support layer 12 of the compressive stress sensor 1 and the shear stress sensor 2 can be Borofloat 33, with a thickness of 300-500um, and a grating film 6 and a metal reflective film 8 with a thickness of 220-300nm on the surface. The grating film 6 and the metal reflective film 8 are both composed of a 100-120nm silicon nitride film, a 20-50nm chromium film layer and a 200-250nm gold film layer (or composed of a 20-50nm chromium film layer and a 200-250nm gold film layer). The area of ​​the cavity 5 is larger than the area of ​​the grating film 6, and the area of ​​the cavity 5 is larger than the area of ​​the metal reflective film 8. The support layer 12 is also provided with a plurality of through holes 9 with a diameter of 800um-1000um, as shown in FIG. Figure 3 and Figure 5 shown.

[0056] In this embodiment, the wafer is connected to the structural layer 11 and the support layer 12 by anodic bonding, and the thickness of the wafer is 340-550 um. Figure 6 Shown is the AA cross-sectional view of the fluid wall shear and compression stress composite array sensor chip.

[0057] Through the above-mentioned fluid wall shear and compressive stress composite array sensor chip, on the one hand, MEMS technology is used to integrate the two-dimensional shear stress sensor and the compressive stress sensor of the fluid wall on the same millimeter-level chip using an integrated synchronous manufacturing process, which simplifies the processing flow. On the other hand, through the palace-shaped array layout, not only the volume and weight of the sensor are reduced, but multiple sensors can also collect data synchronously at different positions to achieve mutual correction of data and high spatial resolution measurement. The palace-shaped array design can also obtain pressure data of multiple spatial points, and calculate the pressure gradient by differential. The shear stress sensor at the centerline position can measure the two-dimensional shear stress in the orthogonal direction, thereby comprehensively obtaining the stress distribution in the fluid. In addition, there is no circuit structure inside the chip, which can be used to measure fluid stress in high temperature environments and underwater. This is suitable for the study of complex flow phenomena and lays the foundation for effectively evaluating the friction resistance and flow noise of the aerodynamic structure of aircraft / aircraft.

[0058] In this embodiment, in the "nine-square grid" array structure, the pressure sensors on the diagonal lines implement self-calibration through the following three steps. The specific steps are as follows:

[0059] Step 1: Error identification: First, the pressure sensors on the diagonal line will compare their data with the data of the sensors at the adjacent positions. When the measured value of a sensor is too different from the value of the adjacent sensor and exceeds the preset threshold range, it is determined that there may be an error. The error may come from system drift or occasional factors. The error identification process aims to accurately detect these abnormal values ​​for subsequent correction.

[0060] Step 2: Data comparison: Next, the diagonal sensor will compare the sensor data of adjacent positions multiple times to further screen the detected deviations. This step can effectively distinguish between real errors and transient anomalies caused by noise or environmental interference. By comparing the normal and abnormal values ​​of adjacent sensors, the source and size of the error can be more accurately confirmed, providing basic data for the calibration step.

[0061] Step 3: Error calibration: After the error is identified and confirmed, the system uses the multi-point measurement values ​​in the array to correct the error value through multi-point interpolation or weighted averaging. The sensor affected by the error will correct its own data based on the average or interpolation results of adjacent sensors to get closer to the actual pressure value. This process ensures the accuracy of the sensor data and improves the measurement consistency of the entire array.

[0062] Through the self-calibration operation, the system can accurately identify and correct measurement errors. By comparing the data of adjacent sensors, the system can detect abnormal values ​​and make corrections, thereby effectively reducing noise interference and avoiding errors caused by environmental factors, sensor drift or external interference. This process significantly improves the measurement accuracy and ensures the reliability and consistency of the data, especially under dynamic changes or extreme high temperature conditions. The self-calibration operation also enhances the robustness of the system, enabling it to adapt to complex environmental conditions including high temperature and underwater, ensuring long-term stable operation. In addition, the nine-square array structure improves the spatial resolution of the system through data fusion of multiple sensor points. Sensors at different locations can collect data synchronously, covering more measurement points, which not only improves the comprehensive perception of pressure distribution, but also enables the system to accurately capture tiny pressure changes, further improving the ability to respond to fluid pressure gradients. By differentially calculating the pressure gradient, the system can provide more detailed and accurate analysis of fluid characteristics. This high-precision data support provides a solid foundation for the analysis of complex flow phenomena, especially for the study of phenomena such as turbulence, boundary layer and flow separation.

[0063] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A fluid wall shear and compressive stress composite array sensor chip, characterized in that: It comprises a plurality of shear stress sensors and pressure stress sensors integrated on a chip, wherein the overall arrangement formation of the shear stress sensors is in the shape of a right cross, and the overall arrangement formation of the pressure stress sensors is in the shape of an X, and the two formations are concentrically superimposed to obtain a square-shaped array layout; the center position of the square-shaped array is a pressure sensor, and a plurality of shear stress sensors are arranged radiating outward along the right cross direction with the central pressure sensor as the radiation center to measure two-dimensional shear stress, and a plurality of pressure stress sensors are arranged radiating outward along the direction of an X with the central pressure sensor as the radiation center to measure gradient pressure.

2. According to claim 1, a fluid wall shear and compressive stress composite array sensor chip is characterized by: The shear stress sensor and the compressive stress sensor are integrated and processed on a chip in an integrated and synchronous manner through MEMS processing technology.

3. According to claim 2, a fluid wall shear and compressive stress composite array sensor chip is characterized in that: The shear stress sensor and the compressive stress sensor both comprise a supporting layer, a cavity and a structural layer. The upper surface of the supporting layer and the lower surface of the structural layer are both provided with a reflective film, and the surface of the cavity is provided with an anti-reflective coating.

4. According to claim 3, a fluid wall shear and compressive stress composite array sensor chip is characterized in that: The support layer of the compressive stress sensor is provided with a plurality of through holes for positioning and fixing the optical fiber, and the internal reflection film is a metal reflection film.

5. The fluid wall shear and compressive stress composite array sensor chip according to claim 4, characterized in that: The structural layer of the shear stress sensor is a floating structure, and its internal reflection film is a grating film; the floating structure includes an elastic beam, a floating element, and a fixed anchor point. The floating element is connected to the fixed anchor point through a circumferentially arranged elastic beam, and can drive the grating film installed on the lower surface of the floating element to produce displacement.

6. The fluid wall shear and compressive stress composite array sensor chip according to claim 5, characterized in that: The reflective film is composed of a silicon nitride film, a chromium film layer and a gold film layer from bottom to top, and a dielectric multilayer film with alternating low and high refractive indices is plated on the surface of the gold film layer, in the order of low refractive medium layer / high refractive medium layer / low refractive medium layer / high refractive medium layer, and each layer is λ / 4 thick.

7. The fluid wall shear and compressive stress composite array sensor chip according to claim 6, characterized in that: The low-refractive dielectric layer of the dielectric multilayer film is Al2O3, and the high-refractive dielectric layer is ZrO2, which is 120nmAl2O3 / 100nmZrO2 / 120nmAl2O3 / 100nmZrO2 respectively.

8. A method for measuring the gradient pressure of the fluid wall shear stress composite array sensor chip according to any one of claims 1 to 7, characterized in that The specific steps are as follows: Arrange multiple compressive stress sensors in an X shape on the chip, and the spacing between adjacent compressive stress sensors in a single radial arrangement direction is equal; Through experiments, it is found that the measured values ​​of each level of pressure stress sensor from the center to the outside show a linear gradient change law; Identify abnormal values ​​and systematic errors based on the gradient variation law, and determine the measurement points where error values ​​are generated; After the error is identified and confirmed, the pressure data of each measuring point is corrected by interpolation or weighted average method to obtain accurate measurement values.

9. The gradient pressure measurement method according to claim 8, characterized in that: The method for identifying abnormal values ​​and systematic errors is: The identification of the abnormal value, for the compressive stress sensors located in the same radiation direction, compares the measured difference of the adjacent compressive stress sensors with the threshold value obtained based on the linear gradient change law, and judges it as an abnormal value when the difference exceeds the threshold value; for the compressive stress sensors located at the same circumferential gradient level, the measured values ​​should be consistent, if there is a difference, the point is judged as an abnormal value; The identification of the system error compares the identified abnormal value with the normal value, screens the deviation range to distinguish between the real error and the instantaneous abnormality caused by noise or environmental interference, and identifies the measurement point of the real error as the system error.

10. The gradient pressure measurement method according to claim 8, characterized in that: The method for correcting the pressure data of each measuring point is to interpolate between the measuring point identified as an abnormal value and the normal value measuring points adjacent to it on both sides, and determine the true pressure value of the abnormal value by multi-point interpolation; by using this method, each abnormal value is corrected to obtain an effective test of the pulsation characteristics of the turbulent boundary layer formation and separation process.

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